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Introduction of ports subdirectory where all ports are moved to

The main change in this release is the introduction of a "ports/"
subdirectory at the top-level of the repository, and all of the ports are
moved here.  In the process the "stmhal" port is renamed to "stm32" to
better reflect the MCU that it targets.  In addition, the STM32 CMSIS and
HAL sources are moved to a new submodule called "stm32lib".

The bytecode has changed in this release, compared to the previous release,
and as a consequence the .mpy version number has increased to version 3.
This means that scripts compiled with the previous mpy-cross must be
recompiled to work with this new version.

There have also been various enhancements and optimisations, such as:
check for valid UTF-8 when creating str objects, support for reverse
special binary operations like __radd__, full domain checking in the math
module, support for floor-division and modulo in the viper emitter,
and addition of stack overflow checking when executing a regex.

The stm32 port sees improved support for F7 MCUs, addition of a new board
B_L475E_IOT01A based on the STM32L475, and support for the Wiznet W5500
chipset along with improved socket behaviour.

A detailed list of changes follows.

py core:
- objstr: startswith, endswith: check arg to be a string
- nlrx86,x64: replace #define of defined() with portable macro usage
- objtype: handle NotImplemented return from binary special methods
- objtype: mp_obj_class_lookup: improve debug logging
- map: remove unused new/free functions
- make m_malloc_fail() have void return type, since it doesn't return
- modstruct: in struct.pack, stop converting if there are no args left
- modstruct: check and prevent buffer-read overflow in struct unpacking
- modstruct: check and prevent buffer-write overflow in struct packing
- nlrthumb: get working again on standard Thumb arch (ie not Thumb2)
- objfloat: fix binary ops with incompatible objects
- obj: fix comparison of float/complex NaN with itself
- objtype: implement fallback for instance inplace special methods
- objtuple: properly implement comparison with incompatible types
- objstr: add check for valid UTF-8 when making a str from bytes
- objlist: properly implement comparison with incompatible types
- runtime0.h: move relational ops to the beginning of mp_binary_op_t
- runtime0.h: move MP_BINARY_OP_DIVMOD to the end of mp_binary_op_t
- objtype: make sure mp_binary_op_method_name has full size again
- runtime0.h: put inplace arith ops in front of normal operations
- builtinhelp: simplify code slightly by extracting object type
- runtime: implement dispatch for "reverse op" special methods
- nlrx86: fix building for Android/x86
- builtinhelp: change signature of help text var from pointer to array
- runtime.h: change empty mp_warning macro so var-args are non empty
- modbuiltins: implement abs() by dispatching to MP_UNARY_OP_ABS
- {objfloat,objcomplex}: optimise MP_UNARY_OP_ABS by reusing variables
- mpconfig.h: add note that using computed gotos in VM is not C99
- objstr: strip: don't strip "\0" by default
- objexcept: prevent infinite recursion when allocating exceptions
- stream: remove unnecessary checks for NULL return from vstr_add_len
- vstr: raise a RuntimeError if fixed vstr buffer overflows
- vm: use lowercase letter at start of exception message
- persistentcode: define mp_raw_code_save_file() for any unix target
- add config option to print warnings/errors to stderr
- objfloat: support raising a negative number to a fractional power
- objset: simplify set and frozenset by separating their locals dicts
- objset: check that RHS of a binary op is a set/frozenset
- objset: include the failed key in a KeyError raised from set.remove
- objtype: change type of enum-to-qstr table to uint16_t to save space
- objstr: make empty bytes object have a null-terminating byte
- mpprint: only check for null string printing when NDEBUG not defined
- objtype: clean up unary- and binary-op enum-to-qstr mapping tables
- persistentcode: bump .mpy version number to version 3
- bc: update opcode_format_table to match the bytecode
- modmath: add full checks for math domain errors
- modmath: convert log2 macro into a function
- formatfloat: don't print the negative sign of a NaN value
- formatfloat: use standard isinf, isnan funcs instead of custom ones
- modbuiltins: use existing utf8_get_char helper in builtin ord func
- emitnative: implement floor-division and modulo for viper emitter
- objtype: use CPython compatible method name for sizeof
- objtype: fit qstrs for special methods in byte type
- objtype: define all special methods if requested
- objtype: introduce MICROPY_PY_ALL_INPLACE_SPECIAL_METHODS

extmod:
- modubinascii: only include uzlib/tinf.h when it's really needed
- modussl_mbedtls: allow to compile with MBEDTLS_DEBUG_C disabled
- machine_pinbase: put PinBase singleton in ROM
- re1.5: upgrade to v0.8.2, adds hook for stack overflow checking
- modure: add stack overflow checking when executing a regex
- uos_dupterm: update uos.dupterm() and helper funcs to have index
- uos_dupterm: swallow any errors from dupterm closing the stream
- vfs: replace VLA in proxy func with small, static sized array
- modussl: add finaliser support for ussl objects
- modussl_mbedtls: allow to compile with unix coverage build

lib:
- add new submodule, stm32lib containing STM32 CMSIS and HAL source
- embed/abort_: use mp_raise_msg helper function
- libm: fix tanhf so that it correctly handles +/- infinity args
- libm: remove implementation of log2f, use MP_NEED_LOG2 instead
- axtls: update, support for SSL_EAGAIN return code
- berkeley-db-1.xx: update, allow to override MINCACHE, DEFPSIZE

drivers:
- memory/spiflash: change from hard-coded soft SPI to generic SPI
- display/ssd1306.py: improve performance of graphics methods
- nrf24l01: make nRF24L01 test script more portable
- display/ssd1306: implement SSD1306_I2C poweron method
- display/ssd1306: make poweron() work the same with SSD1306_SPI
- wiznet5k: improve the performance of socket ops with threading
- wiznet5k: get low-level W5500 driver working

tools:
- upip: upgrade to 1.2.2
- pyboard: use repr() when quoting data in error messages
- pyboard: update docstring for additional device support

tests:
- object_new: better messages, check user __new__() method
- class_new: add checks for __init__ being called and other improvements
- class_new: add another testcase for __new__/__init__ interaction
- class_inplace_op: test for inplace op fallback to normal one
- run-bench-tests: update locations of executables, now in ports/
- class_reverse_op: test for reverse arith ops special methods
- run-tests: skip class_inplace_op for minimal profile
- run-tests: fix copy-paste mistake in var name
- cpydiff: add cases for locals() discrepancies
- extmod: add test for ure regexes leading to infinite recursion
- extmod: add test for '-' in character class in regex
- run-tests: close device under test using "finally"
- net_inet: update tls test to work with CPython and incl new site

unix port:
- rename modsocket.c to modusocket.c
- modusocket: remove #if MICROPY_SOCKET_EXTRA code blocks
- enable MICROPY_PY_REVERSE_SPECIAL_METHODS

stm32 port:
- modmachine: make machine.bootloader() work when MPU is enabled
- modmachine: improve support for sleep/deepsleep on F7 MCUs
- compute PLL freq table during build instead of at run time
- modmachine: for F7 MCU, save power by reducing internal volt reg
- boards/pllvalues.py: make script work with both Python 2 and 3
- Makefile: use lib/stm32lib instead of local cmsis and hal files
- remove cmsis and hal files, they are now a submodule
- Makefile: automatically fetch stm32lib submodule if needed
- update to new STM Cube HAL library
- fix clock initialisation of L4 MCUs
- rename stmhal port directory to stm32
- remove unused usbd_msc.c file
- boards: change remaining stm32f4xx_hal_conf.h to unix line ending
- boards: change linker scripts to use "K" instead of hex byte size
- boards: fix I2C1 pin mapping on NUCLEO_F401RE/F411RE boards
- i2c: when scanning for I2C devices only do 1 probe per address
- modnwwiznet5k: release the GIL on blocking network operations
- boards: add new board B_L475E_IOT01A based on STM32L475
- make-stmconst.py: make sure mpz const data lives in ROM
- timer: make pyb.Timer() instances persistent
- mpconfigport.h: add configuration for max periphs on L4 series
- usbdev: make the USBD callback struct const so it can go in ROM
- usbdev: change static function variable to non-static
- usbdev: put all CDC state in a struct
- usbdev: put all HID state in a struct
- usbdev: simplify CDC tx/rx buffer passing
- usbdev: simplify HID tx/rx buffer passing
- usbdev/core: add state parameter to all callback functions
- usbdev: put all state for the USB device driver in a struct
- usbdev: simplify pointers to MSC state and block dev operations
- usbdev: merge all global USB device state into a single struct
- usbdev: make device descriptor callbacks take a state pointer
- usbdev: move all the USB device descriptor state into its struct
- timer: enable ARPE so that timer freq can be changed smoothly
- modnwwiznet5k: get the IP address of an established socket
- boards: fix typos in stm32f767_af.csv table
- usbd_cdc_interface: don't reset CDC output buf on initialisation
- modnwwiznet5k: implement WIZNET5K.isconnected() method
- modusocket: make getaddrinfo() work when passed an IP address
- modusocket: return OSError(-2) if getaddrinfo fails
- mpconfigport.h: add MICROPY_THREAD_YIELD() macro
- modnwwiznet5k: add support for W5500 Ethernet chip
- modnwwiznet5k: increase SPI bus speed to 42MHz
- modnwwiznet5k: implement stream ioctl for the Wiznet driver
- mphalport: improve efficiency of mp_hal_stdout_tx_strn_cooked
- make uos.dupterm() conform to specs by using extmod version

cc3200 port:
- enable micropython.kbd_intr() method
- use standard implementation of keyboard interrupt

esp8266 port:
- rename axtls_helpers.c to posix_helpers.c
- posix_helpers: set ENOMEM on memory alloc failure
- set DEFPSIZE=1024, MINCACHE=3 for "btree" module
- esp_mphal: send data in chunks to mp_uos_dupterm_tx_strn
- modnetwork: add "bssid" keyword arg to WLAN.connect() method
- modules/webrepl_setup: add info about allowed password length

zephyr port:
- Makefile: revamp "test" target after ports were moved to ports/
- use CONFIG_NET_APP_SETTINGS to setup initial network addresses
- switch to interrupt-driven pull-style console

pic16bit port:
- add definition of SEEK_SET to unistd.h

docs:
- pyboard/tutorial: add "timeout=0" to UART in pass-through example
- more xrefs to "MicroPython port" in glossary
- library/network: fix ref to "socket" module (should be "usocket")
- machine.Signal: improve style/grammar and add usage example
- library: add description of "index" parameter to uos.dupterm()
- library/micropython: fix typo in RST formatting
- library/framebuf.rst: generalise constructor to all colour formats
- btree: describe page caching policy of the underlying implementation
- esp8266/tutorial: update neopixel with example of using 4 bbp
- library/network: clarify usage of "bssid" arg in connect() method
- pyboard/quickref: add info for Switch, RTC, CAN, Accel classes
- pyboard/tutorial: update now that yellow LED also supports PWM
- esp8266/quickref: add quickref info for RTC class
- library: add missing cross-ref links for classes in pyb module
- library/network: update docs to state that W5500 is supported
- uselect: document one-shot polling mode
- usocket: elaborate descriptions
- usocket: document inet_ntop(), inet_pton()
- library/network: add dhcp_hostname parameter
- reference/isr_rules: minor typo correction
- ussl: fix module name refs and use "MicroPython port" term
- esp8266/general: add section on TLS limitations
- usocket: document that settimeout() isn't supported by all ports
- ure: add "|" (alternative) to the list of supported operators
- reference/isr_rules.rst: add tutorial on use of micropython.schedule()

travis:
- use --upgrade when pip is installing cpp-coveralls
- update build command now that stm32 Wiznet config has changed

examples:
- hwconfig_console: add .on()/.off() methods

all:
- convert mp_uint_t to mp_unary_op_t/mp_binary_op_t where appropriate
- convert remaining "mp_uint_t n_args" to "size_t n_args"
- make new ports/ sub-directory and move all ports there
- update Makefiles and others to build with new ports/ dir layout
- remove inclusion of internal py header files
- use NULL instead of "" when calling mp_raise exception helpers

README:
- update "Dependencies" section
- add explicit section on contributing
- add gcc and arm-none-eabi-newlib to list of required components

.gitattributes:
- remove obsolete entries for stmhal/hal, stmhal/cmsis
- add entries for files that will move to ports/ dir

Double precision math library and support on pyboard, and improved ussl

This release brings general improvements and bug fixes to the core and
various ports, as well as documentation additions, clean-ups and better
consistency.  And effort has been made to clean up the source code to
make it more consistent across the core and all ports.

There is a new tool "mpy_bin2res.py" to convert arbitrary (binary) files
to Python resources for inclusion in source code (frozen or otherwise).

The ussl module has seen improvements, including implementation of
server_hostname (for axtls) and server_side mode (for mbedtls).

There is now a double-precision float math library and stmhal has support
to build firmware with software or hardware double-precision.

A detailed list of changes follows.

py core:
- formatfloat: fix number of digits and exponent sign when rounding
- modthread: raise RuntimeError in release() if lock is not acquired
- compile: raise SyntaxError if positional args are given after */**
- objint: support "big" byte-order in int.to_bytes()
- objint: in to_bytes(), allow length arg to be any int and check sign
- compile: fix bug with break/continue in else of optimised for-range
- compile: optimise emitter label indices to save a word of heap
- builtinimport: remove unreachable code for relative imports
- objnamedtuple: simplify and remove use of alloca building namedtuple
- mpprint: remove unreachable check for neg return of mp_format_float
- binary: add missing "break" statements
- runtime: mark m_malloc_fail() as NORETURN
- objstr: remove unnecessary "sign" variable in formatting code
- vm: make "if" control flow more obvious in YIELD_FROM opcode
- modmath: check for zero division in log with 2 args
- makeversionhdr.py: update to parse new release line in docs/conf.py
- objdict: factorise dict accessor helper to reduce code size
- change mp_uint_t to size_t in builtins code
- repl: change mp_uint_t to size_t in repl helpers
- compile: combine arith and bit-shift ops into 1 compile routine
- compile: use switch-case to match token and operator
- objgenerator: allow to hash generators and generator instances
- gc: refactor assertions in gc_free function
- vm: make n_state variable local to just set-up part of VM
- asmx64: support moving a 64-bit immediate to one of top 8 registers
- modmicropython: cast stack_limit value so it prints correctly
- builtinevex: add typechecking of globals/locals args to eval/exec
- py.mk: make berkeley-db C-defs apply only to relevant source files
- mperrno: allow mperrno.h to be correctly included before other hdrs
- mpz: make mpz_is_zero() an inline function
- implement raising a big-int to a negative power
- mkrules.mk: show frozen modules sizes together with executable size
- objtuple: allow to use inplace-multiplication operator on tuples
- objstr: raise an exception for wrong type on RHS of str binary op
- modsys: initial implementation of sys.getsizeof()
- binary.c: fix bug when packing big-endian 'Q' values
- add verbose debug compile-time flag MICROPY_DEBUG_VERBOSE
- binary: change internal bytearray typecode from 0 to 1
- objstringio: prevent offset wraparound for io.BytesIO objects
- objstringio: fix regression with handling SEEK_SET
- stream: seek: Consistently handle negative offset for SEEK_SET
- mkrules.mk: use "find -path" when searching for frozen obj files
- compile: remove unused pn_colon code when compiling func params
- objcomplex: remove unnecessary assignment of variable
- formatfloat: don't post-increment variable that won't be used again
- use "static inline" for funcs that should be inline
- asmthumb: use existing macro to properly clear the D-cache

extmod:
- modussl_axtls: update for axTLS 2.1.3
- modussl_axtls: implement server_hostname arg to wrap_socket()
- move modonewire.c from esp8266 to extmod directory
- modure: if input string is bytes, return bytes results too
- modubinascii: add check for empty buffer passed to hexlify
- modussl_axtls: allow to close ssl stream multiple times
- modussl_mbedtls: support server_side mode
- modussl_mbedtls: when reading and peer wants to close, return 0
- modframebuf: fix invalid stride for odd widths in GS4_HMSB fmt
- modussl_mbedtls: make socket.close() free all TLS resources
- modframebuf: consistently use "col" as name for colour variables
- modussl_mbedtls: implement non-blocking SSL sockets
- machine_signal: fix parsing of invert arg when Pin is first arg
- modframebuf: use correct initialization for .locals_dict
- modlwip: implement setsockopt(IP_ADD_MEMBERSHIP)
- modussl_mbedtls.c: add ussl.getpeercert() method
- modubinascii: rewrite mod_binascii_a2b_base64
- modubinascii: don't post-increment variable that won't be used
- modonewire: rename public module to mp_module_onewire
- for uos.stat interpret st_size member as an unsigned int
- use "static inline" for funcs that should be inline

lib:
- axtls: upgrade to axTLS 2.1.3 + MicroPython patchset
- libm/math: remove implementations of float conversion functions
- add libm_dbl, a double-precision math library, from musl-1.1.16

drivers:
- onewire: move onewire.py, ds18x20.py from esp8266 to drivers
- onewire: enable pull-up when init'ing the 1-wire pin

tools:
- gen-cpydiff: use case description as 3rd-level heading
- pyboard: add license header
- mpy_bin2res: tools to convert binary resources to Python module
- mpy-tool.py: don't generate const_table if it's empty
- mpy-tool.py: fix missing argument in dump() function

tests:
- net_inet/test_tls_sites.py: integration test for SSL connections
- net_inet: add tests for accept and connect in nonblocking mode
- basics: add tests for for-else statement
- net_inet: move tests which don't require full Internet to net_hosted
- connect_nonblock: refactor towards real net_hosted test
- auto detect floating point capabilites of the target
- import: add a test for the builtin __import__ function
- import: update comment now that uPy raises correct exception
- basics/namedtuple1: add test for creating with pos and kw args
- unix/extra_coverage: add test for mp_vprintf with bad fmt spec
- basics: add tests for arithmetic operators precedence
- cpydiff/modules_deque: elaborate workaround
- cpydiff/core_class_mro: move under Classes, add workaround
- cpydiff/core_arguments: move under Functions subsection
- cpydiff/core_class_supermultiple: same cause as core_class_mro
- cpydiff: improve wording, add more workarounds
- cpydiff: add case for str.ljust/rjust
- rename exec1.py to builtin_exec.py
- basics/builtin_exec: test various globals/locals args to exec()

minimal port:
- Makefile: enable gc-sections to remove unused code
- remove unused stmhal include from Makefile
- use size_t for mp_builtin_open argument

unix port:
- modtime: replace strftime() with localtime()
- mpconfigport.mk: update descriptions of readline and TLS options
- Makefile: disable assertions in the standard unix executable
- modjni: convert to mp_rom_map_elem_t
- for uos.stat interpret st_size member as an unsigned int

stmhal port:
- mpconfigport.h: remove config of PY_THREAD_GIL to use default
- make error messages more consistent across peripherals
- add initial implementation of Pin.irq() method
- add .value() method to Switch object, to mirror Pin and Signal
- move pybstdio.c to lib/utils/sys_stdio_mphal.c for common use
- add "quiet timing" enter/exit functions
- make available the _onewire module, for low-level bus control
- modules: provide sym-link to onewire.py driver
- boards/stm32f405.ld: increase FLASH_TEXT to end of 1MiB flash
- sdcard: allow a board to customise the SDIO pins
- add possibility to build with double-precision floating point
- boards: enable double-prec FP on F76x boards
- Makefile: use hardware double-prec FP for MCUs that support it
- Makefile: rename FLOAT_IMPL to MICROPY_FLOAT_IMPL to match C name
- Makefile: add CFLAGS_EXTRA to CFLAGS so cmdline can add options
- mpconfigport.h: allow MICROPY_PY_THREAD to be overridden
- boards: add configuration files for NUCLEO_F429ZI
- boards/NUCLEO_F429ZI: change USB config from HS to FS peripheral
- reduce size of ESPRUINO_PICO build so it fits in flash
- servo: make pyb.Servo(n) map to Pin('Xn') on all MCUs
- servo: don't compile servo code when it's not enabled
- use "static inline" for funcs that should be inline

cc3200 port:
- modusocket: simplify socket.makefile() function
- make non-zero socket timeout work with connect/accept/send
- modusocket: fix connect() when in non-blocking or timeout mode
- use the name MicroPython consistently in code

esp8266 port:
- Makefile: bump axTLS TLS record buffer size to 5K
- Makefile: allow FROZEN_DIR,FROZEN_MPY_DIR to be overridden
- Makefile: add LIB_SRC_C variable to qstr auto-extraction list
- make onewire module and support code usable by other ports
- modonewire: move low-level 1-wire bus code to modonewire.c
- modonewire: make timings static and remove onewire.timings func
- reinstate 1-wire scripts by sym-linking to drivers/onewire/
- move mp_hal_pin_open_drain from esp_mphal.c to machine_pin.c
- enable MICROPY_ENABLE_FINALISER
- README: make "Documentation" a top-level section
- machine_rtc: use correct arithmetic for aligning RTC mem len
- mpconfigport_512k: use terse error messages to get 512k to fit
- mpconfigport.h: make socket a weak link
- modesp: remove unused constants: STA_MODE, etc
- general: add known issue of WiFi RX buffers overflow
- use size_t for mp_builtin_open argument
- fix UART stop bit constants

zephyr port:
- Makefile: rework dependencies and "clean" target
- Makefile: revert prj.conf construction rule to the previous state
- remove long-obsolete machine_ptr_t typedef's
- Makefile: explicitly define default target as "all"
- modusocket: allow to use socketized net_context in upstream
- modusocket: socket, close: switch to native Zephyr socket calls
- modusocket: bind, connect, listen, accept: Swtich to native sockets
- modusocket: send: switch to native sockets
- modusocket: recv: switch to native sockets
- modusocket: fully switch to native Zephyr sockets
- modzephyr: add current_tid() and stacks_analyze() functions
- prj_base.conf: enable CONFIG_INIT_STACKS
- modusocket: update struct sockaddr family field name
- prj_96b_carbon.conf: re-enable networking on Carbon
- modzephyr: add shell_net_iface() function

docs:
- btree: add hints about opening db file and need to flush db
- select: rename to uselect, to match the actual module name
- license: update copyright year
- esp8266/tutorial/intro: discourage use of 512kb firmwares
- esp8266/tutorial/intro: Sphinx requires blank lines around literal blocks
- conf.py: include 3 levels of ToC in latexpdf output
- gc: mark mem_alloc()/mem_free() as uPy-specific
- gc: document gc.threshold() function
- builtins: list builtin exceptions
- conf.py: set default_role = 'any'
- lcd160cr: group related constants together and use full sentences
- ref/speed_python: update and make more hardware-neutral
- library/gc: fix grammar and improve readability of gc.threshold()
- move all ports docs to the single ToC
- topindex.html: remove link to wipy.io, it's no longer available
- conf.py: add .venv dir to exclude_patterns
- move topindex.html to templates/ subdir
- differences/index_template: use consistent heading casing
- builtins: add AssertionError, SyntaxError, ZeroDivisionError
- add glossary
- conf.py: switch to "new" format of intersphinx_mapping
- conf.py: add file for global replacements definition
- library: add CPython docs xref to each pertinent module
- replace.inc: add |see_cpython|, to xref individual symbols from CPython
- conf.py: set "version" and "release" to the same value
- *_index: drop "Indices and tables" pseudo-section
- pyboard: move hardware info into General Info chapter
- uerrno: document "uerrno" module
- esp8266/general.rst: fix name of NTP module
- pyboard: move info about using Windows from topindex to general
- uzlib: update description of decompress() and mention DecompIO
- pyboard/tutorial/amp_skin: add example for playing large WAV files
- library/ubinascii: update base64 docs
- library/usocket: move socket.error to its own section
- library/usocket: describe complete information on address formats
- glossary: elaborate on possible MicroPython port differences
- glossary: fix typos in micropython-lib paragraph
- index: rewrite introduction paragraph to avoid confusion
- use the name MicroPython consistently in documentation
- consistently link to micropython-lib in glossary

all:
- make more use of mp_raise_{msg,TypeError,ValueError} helpers
- unify header guard usage
- remove trailing spaces, per coding conventions
- don't include system errno.h when it's not needed
- use the name MicroPython consistently in comments
- make use of $(TOP) variable in Makefiles, instead of ".."
- raise exceptions via mp_raise_XXX
- make static dicts use mp_rom_map_elem_t type and MP_ROM_xxx macros

README:
- mention support for bytecode and frozen bytecode
- improve description of precompiled bytecode; mention mpy-cross

CODECONVENTIONS:
- clarify MicroPython changes sign-off process
- start to describe docs conventions
- describe docs use of markup for None/True/False

travis:
- build STM32F769DISC board instead of F7DISC to test dbl-prec FP
- pin cpp-coveralls at 0.3.12

Fixes for stmhal USB mass storage, lwIP bindings and VFS regressions

This release provides an important fix for the USB mass storage device in
the stmhal port by implementing the SCSI SYNCHRONIZE_CACHE command, which
is now require by some Operating Systems.  There are also fixes for the
lwIP bindings to improve non-blocking sockets and error codes.  The VFS has
some regressions fixed including the ability to statvfs the root.

All changes are listed below.

py core:
- modbuiltins: add core-provided version of input() function
- objstr: catch case of negative "maxsplit" arg to str.rsplit()
- persistentcode: allow to compile with complex numbers disabled
- objstr: allow to compile with obj-repr D, and unicode disabled
- modsys: allow to compile with obj-repr D and PY_ATTRTUPLE disabled
- provide mp_decode_uint_skip() to help reduce stack usage
- makeqstrdefs.py: make script run correctly with Python 2.6
- objstringio: if created from immutable object, follow copy on write policy

extmod:
- modlwip: connect: for non-blocking mode, return EINPROGRESS
- modlwip: fix error codes for duplicate calls to connect()
- modlwip: accept: fix error code for non-blocking mode
- vfs: allow to statvfs the root directory
- vfs: allow "buffering" and "encoding" args to VFS's open()
- modframebuf: fix signed/unsigned comparison pendantic warning

lib:
- libm: use isfinite instead of finitef, for C99 compatibility
- utils/interrupt_char: remove support for KBD_EXCEPTION disabled

tests:
- basics/string_rsplit: add tests for negative "maxsplit" argument
- float: convert "sys.exit()" to "raise SystemExit"
- float/builtin_float_minmax: PEP8 fixes
- basics: convert "sys.exit()" to "raise SystemExit"
- convert remaining "sys.exit()" to "raise SystemExit"

unix port:
- convert to use core-provided version of built-in import()
- Makefile: replace references to make with $(MAKE)

windows port:
- convert to use core-provided version of built-in import()

qemu-arm port:
- Makefile: adjust object-file lists to get correct dependencies
- enable micropython.mem_*() functions to allow more tests

stmhal port:
- boards: enable DAC for NUCLEO_F767ZI board
- add support for NUCLEO_F446RE board
- pass USB handler as parameter to allow more than one USB handler
- usb: use local USB handler variable in Start-of-Frame handler
- usb: make state for USB device private to top-level USB driver
- usbdev: for MSC implement SCSI SYNCHRONIZE_CACHE command
- convert from using stmhal's input() to core provided version

cc3200 port:
- convert from using stmhal's input() to core provided version

teensy port:
- convert from using stmhal's input() to core provided version

esp8266 port:
- Makefile: replace references to make with $(MAKE)
- Makefile: add clean-modules target
- convert from using stmhal's input() to core provided version

zephyr port:
- modusocket: getaddrinfo: Fix mp_obj_len() usage
- define MICROPY_PY_SYS_PLATFORM (to "zephyr")
- machine_pin: use native Zephyr types for Zephyr API calls

docs:
- machine.Pin: remove out_value() method
- machine.Pin: add on() and off() methods
- esp8266: consistently replace Pin.high/low methods with .on/off
- esp8266/quickref: polish Pin.on()/off() examples
- network: move confusingly-named cc3200 Server class to its reference
- uos: deconditionalize, remove minor port-specific details
- uos: move cc3200 port legacy VFS mounting functions to its ref doc
- machine: sort machine classes in logical order, not alphabetically
- network: first step to describe standard network class interface

examples:
- embedding: use core-provided KeyboardInterrupt object

New VFS subsystem and scheduling framework, and less need for the heap

This release adds some fundamental new components, allows for more Python
operations without using the heap and has reduced code size and stack
usage.

Changes in the way iterators are handled allows to iterate without
allocating on the heap for the types: tuple, list, str, bytes, bytearray,
array, dict, set, frozenset.  It also allows to call the builtins all, any,
min max and sum without allocating heap memory for the iterator argument.
And improvements to the handling of super() means that super().foo() method
calls are now heap-less.

A new generic VFS subsystem has been added which allows to mount arbitrary
filesystems (even written in Python) at the root or at a mount-point within
the root.  The FatFS driver has been replaced with an object-oriented
version (oofatfs) which allows a fully customisable filesystem layout.

A scheduling framework has been implemented in the core which gives the
ability to schedule callbacks to be called "as soon as possible".  This
allows ports to implement "soft IRQs" which allow the programmer to
allocate memory during an interrupt handler, at the cost of some
performance related to response time of the handler.  The new
micropython.schedule() function gives access to the scheduler.

Other improvements to the core include: consts can now be big-nums, for
example "X = const(1 << 100)"; addition of "help('modules')" to list
available modules; stack usage reduced for a Python call by 8 bytes on ARM
Cortex-M architectures; micropython.kbd_intr() function added to disable
Ctrl-C capture; addition of uio.resource_stream(); mpy-cross is built
automatically if needed; a helper tool mpy_cross_all.py is added to run
mpy-cross on an entire project.

The bytecode has changed in this version so existing .mpy files will need
recompiling.  There have also been some changes to the C API, most notably
with mp_uint_t changed to size_t in many places.

In the extended modules the following main changes have been made: addition
of machine.Signal class to allow inversion on a Pin; framebuf has new
formats of the form MONO_xxx; addition of uselect.ipoll() for allocation-
free polling; addition of uos.ilistdir() for efficient iteration of a
directory listing; machine.Pin high/low methods are renamed to on/off in
esp8266 and zephyr (this is a backwards-incompatible change);
machine.time_pulse_us() function no longer throws exceptions, but returns
negative values instead.

For stmhal the pyb.fault_debug() function is added, and default behaviour
for a hard-fault is now an immediate reset.  There is better support for F7
MCUs, in particular DMA and SD card support.  A bug has been fixed with the
USB VCP (USB serial) where it would in rare cases (usually when the host PC
was under load) would lose characters.  Pyboard now automatically mounts
all available partitions on the SD card.  Multithreading has been
implemented and is available via the _thread module, but this feature is
disabled by default and must be enabled at compile time using the
MICROPY_THREAD and MICROPY_THREAD_GIL options.  The ability to skip booting
from SD card is now available by creating an empty file on the flash called
"SKIPSD".

The cc3200 port has had some backwards incompatible changes, in particular
with I2C, Pin, UART and uos.  Please see the documentation for the new
behaviour.

The esp8266 port has had a change in the size of the firmware in order to
accommodate additional features.  As such the filesystem for this version
is incompatible with v1.8.7 and a device requires backup and erasure before
flashing this version.  Soft IRQs are now implemented for Pin and Timer
callbacks, along with the general improvements described above.

In the documentation there is now a section describing the differences
between MicroPython and CPython.  And code coverage is up to 98% across py/
and extmod/.

Changes in code size (in bytes) between v1.8.7 and this version are:

   bare-arm: -1104
    minimal: -1324
   unix x64: -1115
unix nanbox: -11106
     stmhal: +18116
     cc3200: +1032
    esp8266: +3060

Note that stmhal has increased significantly due to the addition of frozen
bytecode and the LCD160CR driver.

A detailed list of changes follows.

py core:
- builtinimport: raise ValueError for bad relative import, per CPython
- builtinimport: remove unreachable code and change obj-import comment
- runtime: refactor assert(0) to improve coverage
- runtime: fix handling of throw() when resuming generator
- objgenerator: when throwing an object, don't make an exc instance
- objgenerator: don't raise RuntimeError if GeneratorExit ignored
- parse: refactor code to remove assert(0)'s
- emitnative: remove assert(0)'s or replace with mp_not_implemented
- objexcept: replace if-cond and assert(0) with simple assert
- runtime: refactor default case of switch to remove assert(0)
- binary: mp_binary_get_size: Raise error on unsupported typecodes
- formatfloat: remove unreachable code
- objint_mpz: refactor switch-statement to remove unreachable default
- mpz: implement mpz_set_from_bytes() as a foundation for int.from_bytes()
- objint: from_bytes(): implement "byteorder" param and arbitrary precision
- objint_longlong: add stub for mp_obj_int_from_bytes_impl()
- add builtin help function to core, with default help msg
- move weak-link map to objmodule.c, and expose module maps as public
- builtinhelp: implement help('modules') to list available modules
- objint: fix left-shift overflow in checking for large int
- objmodule: move module init/deinit code into runtime functions
- objstr: optimize string concatenation with empty string
- showbc: make sure to set the const_table before printing bytecode
- py.mk: add CFLAGS_MOD flag to set config file for FatFs
- objstringio: allow to specify initial capacity by passing numeric argument
- objset: make inplace binary operators actually modify the set
- objfloat: raise ZeroDivisionError for 0 to negative power
- objcomplex: correctly handle case of 0j to power of something
- objset: fix inplace binary ops so frozensets are not modified
- added optimised support for 3-argument calls to builtin.pow()
- objstr: give correct behaviour when passing a dict to %-formatting
- mpconfig.h: move PY_BUILTINS_POW3 config option to diff part of file
- objstr: convert some instances of mp_uint_t to size_t
- objcomplex: fix typo in ternary expression
- asmxtensa.h: explicitly cast args to 32-bits so left-shift is legal
- map: change mp_uint_t to size_t where appropriate
- nlr: fix execstack builds for ARM
- objtype: add __delattr__/__setattr__ configured by MICROPY_PY_DELATTR_SETATTR
- emitbc: produce correct line number info for large bytecode chunks
- objtype: replace non-ASCII single-quote char with ASCII version
- modthread: use system-provided mutexs for _thread locks
- vm: add MICROPY_PY_THREAD_GIL_VM_DIVISOR option
- runtime: convert mp_uint_t to size_t where appropriate
- mpz: convert mp_uint_t to size_t where appropriate
- mpz: remove obsolete declaration of mpz_as_str_size
- mpz: change type of "base" args from mp_uint_t to unsigned int
- persistentcode: replace mp_uint_t with size_t where appropriate
- objtuple: convert mp_uint_t to size_t where appropriate
- objlist: convert mp_uint_t to size_t where appropriate
- objdict: convert mp_uint_t to size_t where appropriate
- objset: convert mp_uint_t to size_t where appropriate
- objstr: convert mp_uint_t to size_t (and use int) where appropriate
- objarray: convert mp_uint_t to size_t where appropriate
- objfun: convert mp_uint_t to size_t where appropriate
- objclosure: convert mp_uint_t to size_t where appropriate
- objexcept: convert mp_uint_t to size_t where appropriate
- objint: convert mp_uint_t to size_t where appropriate
- vm: convert mp_uint_t to size_t where appropriate
- add iter_buf to getiter type method
- allow bytecode/native to put iter_buf on stack for simple for loops
- make FOR_ITER opcode pop 1+4 slots from the stack when finished
- optimise storage of iterator so it takes only 4 slots on Py stack
- remove unused "use_stack" argument from for_iter_end emit function
- runtime: optimise case of identity iterator so it doesn't alloc RAM
- compile: optimise list/dict/set comprehensions to use stack iter
- de-optimise some uses of mp_getiter, so they don't use the C stack
- grammar: group no-compile grammar rules together to shrink tables
- lexer: don't generate string representation for period or ellipsis
- persistentcode: bump .mpy version due to change in bytecode
- lexer: simplify handling of indenting of very first token
- lexer: move check for keyword to name-tokenising block
- lexer: use strcmp to make keyword searching more efficient
- lexer: simplify handling of line-continuation error
- do adjacent str/bytes literal concatenation in lexer, not compiler
- lexer: convert mp_uint_t to size_t where appropriate
- grammar: remove unused rule
- objlist: for list slice assignment, allow RHS to be a tuple or list
- moduerrno: make uerrno.errorcode dict configurable
- moduerrno: make list of errno codes configurable
- parse: allow parser/compiler consts to be bignums
- create str/bytes objects in the parser, not the compiler
- parse: simplify handling of errors by raising them directly
- runtime: mp_raise_msg(): Accept NULL argument for message
- objarray: disallow slice-assignment to read-only memoryview
- map: fix bugs with deletion of elements from OrderedDict
- move locals/globals dicts to the thread-specific state
- nlr.h: mark nlr_jump_fail as NORETURN
- nlrxtensa: convert from assembler to C file with inline asm
- nlrx64: convert from assembler to C file with inline asm
- nlrx86: convert from assembler to C file with inline asm
- py.mk: force nlr files to be compiled with -Os
- modsys: use MP_SMALL_INT_MAX for sys.maxsize in case of LONGINT_IMPL_NONE
- runtime.c: remove optimization of '*a,=b', it caused a bug
- use mp_obj_get_array where sequence may be a tuple or a list
- nlrx86: add workaround for Zephyr
- nlrx64: fixes to support Mac OS
- objint_longlong: implement mp_obj_int_from_bytes_impl()
- allow lexer to raise exceptions during construction
- objint: allow to print long-long ints without using the heap
- emitnative: use assertions and mp_not_implemented correctly
- emitnative: remove obsolete commented out code
- mpprint: fix int formatting so "+" is printed for 0-valued integer
- mkrules.mk: remove special check for "-B" in qstr auto generation
- objstr: fix eager optimisation of str/bytes addition
- reduce size of mp_code_state_t structure
- provide mp_decode_uint_value to help optimise stack usage
- objstr: use better msg in bad implicit str/bytes conversion exception
- add micropython.schedule() function and associated runtime code
- vm: don't release the GIL if the scheduler is locked
- bc: provide better error message for an unexpected keyword argument
- use size_t as len argument and return type of mp_get_index
- sequence: convert mp_uint_t to size_t where appropriate
- define and use MP_OBJ_ITER_BUF_NSLOTS to get size of stack iter buf
- lexer: remove obsolete comment, since lexer can now raise exceptions
- modmath: allow trunc/ceil/floor to return a big int if necessary
- objint: handle special case of -0 when classifying fp as int
- modbuiltins: for round() builtin use nearbyint instead of round
- modbuiltins: allow round() to return a big int if necessary
- objtype: use size_t where appropriate, instead of mp_uint_t or uint
- objnamedtuple: use size_t where appropriate, instead of mp_uint_t
- use mp_locals/mp_globals accessor funcs instead of MP_STATE_CTX
- remove MP_STATE_CTX, use MP_STATE_THREAD instead (it's an alias)
- objarray: use mp_obj_str_get_str instead of mp_obj_str_get_data
- nlrx86: better check for Zephyr (requires 1.7)
- obj: change mp_uint_t to size_t for mp_obj_get_array_fixed_n len arg
- vm: fix VM opcode tracing to print correct stack pointer
- compile: when compiling super(), handle closed-over self variable
- objmap: convert mp_uint_t to size_t
- use mp_raise_TypeError/mp_raise_ValueError helpers where possible
- lexer: simplify and reduce code size for operator tokenising
- compile: simplify syntax-error messages for illegal assignments
- shorten a couple of error messages
- compile: provide terse error message for invalid dict/set literals
- convert mp_uint_t to size_t for tuple/list accessors
- change mp_uint_t to size_t for mp_obj_str_get_data len arg
- objzip: convert mp_uint_t to size_t
- obj.h: make sequence grow more efficient and support overlapping
- objstr: use MICROPY_FULL_CHECKS for range checking when constructing bytes
- add very simple but correct hashing for float and complex numbers
- objint: consolidate mp_obj_new_int_from_float to one implementation
- raise a ValueError if range() step is zero
- objtuple: add support for inplace add (same as normal add)
- make sure that static emg-exc-buffer is aligned to size of mp_obj_t
- runtime: when init'ing kbd intr exc, use tuple ptr instead of object
- objint: extract small int value directly because type is known
- objint: use unsigned arithmetic when formatting an integer
- obj: clean up and add comments describing mp_obj_type_t struct
- optimise types for common case where type has a single parent type
- objfloat: add implementation of high-quality float hashing
- nlrsetjmp: add check for failed NLR jump
- gc: execute finaliser code in a protected environment
- modmicropython: add micropython.kbd_intr() function
- reduce str/repr precision of float numbers when floats are 30-bit
- objtype: mp_obj_new_super doesn't need to be public, so inline it
- compile: don't do unnecessary check if parse node is a struct
- compile: extract parse-node kind at start of func for efficiency
- compile: add COMP_RETURN_IF_EXPR option to enable return-if-else opt
- compile: don't do unnecessary check if iter parse node is a struct
- compile: refactor handling of special super() call
- add LOAD_SUPER_METHOD bytecode to allow heap-free super meth calls
- mpz: strip trailing zeros from mpz value when set from bytes
- mpz: in mpn_sub, use existing function to remove trailing zeros
- cleanup use of global DEBUG preprocessor definition
- modio: implement uio.resource_stream(package, resource_path)
- objint: in int.from_bytes, only create big-int if really needed
- modio: resource_stream: Implement "package" param handling
- binary: handle storing big-ints to all arrays types
- lexer: simplify lexer startup by using dummy bytes and next_char()
- mkrules.mk: add dependency of .mpy files upon mpy-cross
- lexer: process CR earlier to allow newlines checks on chr1
- modsys: update conditionals for code referencing sys.stdout
- objstringio: fix StringIO reads at or beyond EOF
- sequence: fix boundary errors when slicing with a negative step
- objrange: fix slicing of range when step of slice is negative
- mkenv.mk: use $(TOP) instead of ".." to reference tools, mpy-cross
- vm: fix bug with stackless mode and unwinding of exceptions
- vm: fix bug with unwind jump popping the iterator from a for loop
- emitbc: fix bug with BC emitter computing Python stack size
- mkrules.mk: fix auto-qstr generation when "make -B" is used
- objstringio: catch mp_uint_t overflow of stream position in write()
- move BYTES_PER_WORD definition from ports to py/mpconfig.h

extmod:
- modframebuf: optimize fill_rect subroutine call
- modframebuf: clip pixels drawn by line method
- modframebuf: add GS4_HMSB format
- vfs_fat: rework so it can optionally use OO version of FatFS
- rename vfs_fat_file.h to vfs_fat.h
- add generic VFS sub-system
- vfs_fat: rework to support new generic VFS sub-system
- vfs: add ability for VFS sub-system to import using VfsFat
- modlwip: add socket.readinto() method
- vfs: expose mp_vfs_mount_t type
- vfs_fat: use SECSIZE macro to determine FatFs sector size
- machine_signal: implement "Signal" abstraction for machine module
- vfs_fat: update to use FF_DIR instead of DIR
- vfs: expose lookup_path_raw as mp_vfs_lookup_path
- vfs_fat: remove MICROPY_READER_FATFS component
- vfs_fat: remove MICROPY_FSUSERMOUNT_ADHOC config option
- remove MICROPY_FSUSERMOUNT and related files
- vfs_fat: remove MICROPY_FATFS_OO config option
- merge old fsusermount.h header into vfs.h and vfs_fat.h
- vfs_fat: remove unused fatfs_builtin_open function
- vfs_fat: remove unused function fat_vfs_listdir
- vfs_reader: fix use of NLR by popping context
- vfs_fat.c: use explicit include path for timeutils.h
- machine_pulse: make time_pulse_us() not throw exceptions
- machine_spi: remove EVENT_POLL_HOOK from soft-SPI transfer func
- machine_signal: implement Signal .on() and .off() methods
- vfs: allow to mount a block device, not just a VFS object
- vfs: raise OSError(EEXIST) on attempt to mkdir a mount point
- vfs: allow to stat the root directory
- modlwip: add my copyright
- modurandom: use mp_raise_ValueError()
- modutimeq: make scheduling fair (round-robin)
- modutimeq: add peektime() function (provisional)
- vfs_fat: remove obsolete and unused str/len members
- vfs_fat: allow to compile with MICROPY_VFS_FAT disabled
- vfs: rewrite path lookup algo to support relative paths from root
- modframebuf: add support for monochrome horizontal format
- utime_mphal: don't exit/enter the GIL in generic sleep functions
- modlwip: use mp_obj_str_get_str instead of mp_obj_str_get_data
- vfs_fat: fix calculation of total blocks in statvfs
- moduselect: update to use size_t for array accessor
- update for changes to mp_obj_str_get_data
- modframebuf: make monochrome bitmap formats start with MONO_
- machine_signal: support all Pin's arguments to the constructor
- machine_signal: rename "inverted" arg to "invert", it's shorter
- moductypes: fix bigint handling for 32-bit ports
- crypto-algorithms/sha256: remove non-standard memory.h header
- moduselect: convert to MP_ROM_QSTR and friends
- moduselect: refactor towards introduction of poll.ipoll()
- moduselect: implement ipoll() method for alloc-free polling
- modlwip: getaddrinfo: Allow to accept all 6 standard params
- modlwip: ioctl POLL: Fix handling of peer closed socket
- vfs: allow a VFS to be mounted at the root dir
- vfs: implement mp_vfs_ilistdir()
- vfs_fat: replace listdir() with implementation of ilistdir()
- vfs: use MP_S_IFDIR, MP_S_IFREG consts instead of magic numbers
- vfs_fat_misc: remove dot-dirs filter since FatFS already does it

lib:
- utils: remove old pyhelp helper, replaced with py/builtinhelp.c
- utils/pyexec: only print help prompt if HELP feature is enabled
- oofatfs: add OO version of FatFS library
- fatfs: remove old fatfs library component, it's replaced by oofatfs
- oofatfs/ffconf.h: allow to configure FS_EXFAT option
- oofatfs/ffconf.h: add MICROPY_FATFS_NORTC option
- utils/pyexec: allow to compile when the uPy compiler is disabled
- utils/pyexec: refactor to put lexer constructors all in one place
- memzip: make lexer constructor raise exception when file not found
- utils/pyexec: fix bug with pyexec_file not setting flag for source
- libm: add implementation of nearbyintf, from musl-1.1.16
- netutils: update for changes to mp_obj_str_get_data
- utils/pyexec: update event-driven REPL to match non-event REPL

drivers:
- fix some minor spelling mistakes
- display: add driver and test for uPy LCD160CR display
- memory: add SPI flash driver, written in C
- display/lcd160cr: use correct variable in set_power()
- display/lcd160cr: fix bugs with lcd.get_pixel()
- display/lcd160cr: fix bug with save_to_flash method
- display/lcd160cr: add check that JPEG size is less than 65536
- nrf24l01: update to work on newer ports, using machine, utime
- display/lcd160cr: fix get_line method and enhance screen_dump
- display/lcd160cr_test: allow test to take orientation parameter
- replace deprecated Pin.high()/low() methods with .__call__(1/0)

tools:
- tinytest-codegen.py: blacklist heapalloc_str.py test for qemu-arm
- upip: update to 1.1.5. Better and more user-friendly error handling
- add gen-cpydiff.py to generate docs differences
- gen-cpydiff.py: set the Python import path to find test modules
- gen-cpydiff.py: configurable CPython and micropython executables
- tinytest-codegen: update for recent test renaming ("intbig" suffix)
- pyboard: tighten up Pyboard object closure on errors
- pyboard: add "exec" and "execpty" pseudo-devices support
- pyboard: execpty: Use shell=False to workaround some curdir issues
- pyboard: processPtyToTerminal: Add workaround for PySerial bug
- pyboard: provide more details when expected reply not received
- mpy-tool: make work if run from another directory
- upip: upgrade to 1.1.6, supports commented lines in requirements.txt
- upip: upgrade to 1.2
- mpy-tool.py: use MP_ROM_xxx macros to support nanbox builds
- mpy_cross_all.py: helper tool to run mpy-cross on the entire project
- mpy-tool.py: fix regression with freezing floats in obj repr C

tests:
- add feature check for "const" keyword and skip related tests
- update test suite to be compatible with CPython 3.6
- improve stream.c test coverage
- import: improve builtinimport.c test coverage
- improve frozen import test coverage
- update tests, and add new ones, for recent generator tweaks
- io: improve test coverage of io.BufferedWriter
- basics: improve runtime.c test coverage
- extmod: improve test coverage of ure module
- float: add test for assigning to attribute of complex number
- extmod/framebuf1: add test for no-op fill_rect
- micropython/opt_level: add test for opt_level 3
- misc/non_compliant: add test for inability to assign func attrs
- basics: add test for assignment of attribute to bound method
- add test for int.from_bytes() for arbitrary-precision integer
- heapalloc_int_from_bytes: test that int.from_bytes() can work w/o alloc
- add test for builtin help function
- basics/builtin_help: add test for help('modules')
- make sure special tests can be skipped as well
- extmod/framebuf4: add tests for GS4_HMSB framebuf format
- extmod/framebuf1: fix test for framebuf invalid constructor
- extmod: add test for ure debug printing when compiling a regex
- heapalloc_str: test for alloc-free string operations
- extmod: update vfs_fat tests for new OO FatFs library
- extmod/vfs_fat: update tests to work with new VFS sub-system
- extmod/vfs_fat_ramdisk: make it work on pyboard
- run-tests: skip frozenset tests if set literal syntax is not available
- basics/zip: make skippable
- thread: make thread_exc2 runable on baremetal
- thread: fix stack size test so tests run reliably on baremetal
- heapalloc_bytesio: test for BytesIO with preallocates space
- basics/set_binop: add tests for inplace set operations
- float: add tests for zero to a negative power
- split tests for 2- and 3-arg pow()
- basics/string_format_modulo: add more tests for dict formatting
- pyb: adjust tests so they can run on PYB and PYBLITE
- misc: add test for line number printing with large bytecode chunk
- add option to not clear MICROPYPATH when running tests
- run-tests: allow to skip tests using async/await keywords
- comprehension1, containment: split set tests to separate files
- builtin_dir: the most expected thing in sys is exit, test for it
- basic/[a-f]*: make skippable
- dict_fromkeys: revert to use reversed() to run in native codegen mode
- extmod: make tests skippable
- thread: replace busy waiting loops with a loop that sleeps
- thread: add stress-test for creating many threads
- gen_yield_from_close: use range() instead of reversed()
- basic/: make various tests skippable
- cmdline: update tests to pass with latest changes to bytecode
- cmdline/cmd_showbc: update to work with recent changes
- micropython: add test for iterating with the heap locked
- micropython/heapalloc_iter: add tests for contains and unpack
- cmdline: update cmd_parsetree test for changes to grammar order
- cmdline/cmd_parsetree: update to work with changes to grammar
- basics/string_join: add more tests for string concatenation
- heapalloc_exc_raise.py: heap alloc test for raising/catching exc
- cpydiff: add initial set of tests for uPy-CPython differences
- cpydiff: add a test for storing iterable to a list slice
- micropython: add test for consts that are bignums
- extmod: add test for machine.Signal class
- basics: add further tests for OrderedDict
- run-tests: check for big int availability and skip related tests
- basic: split tests into working with small ints and not working
- float/complex1: split out intbig test
- float2int*: suffix with _intbig, don't run on any other int type
- string_format_modulo2: split off intbig test
- basics/string_join.py: add test case where argument is not iterable
- basics/unpack1.py: test if *a, = b copies b when b is a list
- micropython/: split off intbig tests
- uctypes_array_assign_native_le: split off intbig part
- basic: make various tests skippable
- float: make various tests skippable
- extmod: add very basic feature test for ussl module
- extmod: add websocket tests
- dict_fromkeys: split out skippable part
- micropython: make uio-using tests skippable
- micropython/heapalloc_traceback: fix backtrace line # after refactor
- micropython/opt_level: clarify the expected output for opt_level == 3
- feature_check/int_big: rework "big int" detection
- basics/fun_error: split out skippable test
- extmod: rename websocket test to websocket_basic
- misc/: make few tests skippable
- extmod: add a test for core VFS functionality, sans any filesystem
- extmod/vfs_basic: add more tests for basic VFS functionality
- extmod: improve re1.5/recursiveloop.c test coverage
- improve binary.c test coverage
- basics/struct_micropython: add test for 'S' typecode in ustruct
- run-tests: re-instate skipping of doubleprec test on pyboard
- extmod/vfs_basic: unmount all existing devices before doing test
- extmod: improve tinfgzip.c test coverage
- micropython/viper_error: add more tests to improve coverage
- basics/string_format2: adjust comment now that tests succeed
- basics: add test for string module formatting with int argument
- basics: move string-modulo-format int tests to dedicated file
- basics/bytes_add: add tests for optimised bytes addition
- micropython: add tests for micropython.schedule()
- heapalloc_str: test no-replacement case for str.replace()
- float: add tests for math funcs that return ints
- float: add tests for round() of inf, nan and large number
- basics: add test for super() when self is closed over
- basics: add tests for list and bytearray growing using themselves
- run-tests: be sure to close Pyboard object on completion
- vfs_fat_fileio.py is too big to be parsed in 16K heap, split in 2
- extmod/vfs_fat_fileio*: improve skippability
- float/byte*_construct: skip on missing array module
- micropython/heapalloc_iter: improve skippability
- run-tests: introduce generic "minimal" target
- float: add tests for hashing float and complex numbers
- run-tests: update names of tests that may need skipping
- basics: add tests for raising ValueError when range() gets 0 step
- basics: add test for tuple inplace add
- extmod/utimeq1: improve coverage of utimeq module
- run-tests: search feature checks wrt to main script location
- run-tests: don't post-process CRASH result in any way
- micropython: add test for micropython.kbd_intr()
- add tests for calling super and loading a method directly
- basics: add tests for int.from_bytes when src has trailing zeros
- cpydiff/core_arguments: fill in cause/workaround
- cpydiff/core_function_userattr: clarify, fill in cause and workaround
- cpydiff/core_import_prereg: fill in cause and workaround
- io/resource_stream: add test for uio.resource_stream()
- cpydiff/core_import_path: test showing difference in package.__path__
- cpydiff/core_import_split_ns_pkgs: test for split namespace packages
- cpydiff/core_function_unpacking: fill in workaround
- extmod: add more tests for VFS FAT
- extmod: add some more VFS tests
- micropython: add test for int.from_bytes with many zero bytes
- move super-as-local test from cpydiff to basic tests
- basics: update array test for big-int with lL typecodes
- basics: add memoryview test for big ints
- basics/lexer: add lexer tests for input starting with newlines
- extmod: make some vfs tests fully unmount FSs before running
- extmod/vfs: update tests to reflect new ilistdir() method
- basics/lexer: add line continuation tests for lexer
- extmod/vfs_fat: add test for ilistdir of a non-existent directory
- extmod/vfs_fat_more: make skippable is uos is not available
- io/bytesio_ext: test read() after seek() past end of BytesIO object
- basics/list_slice_3arg: add more tests for negative slicing
- basics/builtin_range: add tests for negative slicing of range
- basics: add more tests for unwind jumps from within a try-finally

mpy-cross:
- main: move lexer constructor to within NLR handler block
- fix compiler detection for including windows/fmode.c
- Makefile: override undefine any inherited variables
- Makefile: guard "override undefine" by test for make feature

bare-arm port:
- main: move lexer constructor to within NLR handler block
- Makefile: change C standard from gnu99 to c99

minimal port:
- update frozentest.mpy file for new .mpy version
- add ability and description to build without the compiler
- main: move lexer constructor to within NLR handler block
- Makefile: change C standard from gnu99 to c99
- main: make Cortex-M vector table constant

unix port:
- coverage: move coverage #if guard back to top of file
- enable builtin help function in coverage build
- enable MICROPY_PY_BUILTINS_HELP_MODULES in coverage build
- switch to OO version of FatFS library
- get minimal version compiling again
- change to use new generic VFS sub-system in coverage build
- fatfs_port: include new oofatfs header
- mpconfigport.h: remove obsolete MICROPY_FATFS_VOLUMES config
- modos: remove VfsFat from uos module, it's now in uos_vfs module
- make stack be non-executable
- fix freedos port build problems
- main: properly handle MICROPYPATH starting with ':'
- moduselect: implement ipoll() method with no-allocation policy
- modmachine: add Signal class to machine module
- remove remaining, obsolete traces of GNU readline support
- moduselect: properly implement ipoll object iteration
- main: refactor to put lexer constructors all in one place
- use mp_handle_pending() in time.sleep()
- coverage: enable scheduler and add tests for it
- use mp_obj_str_get_str instead of mp_obj_str_get_data
- convert mp_uint_t to size_t for use of mp_obj_list_get
- convert mp_uint_t to size_t in alloc.c
- enabled high-quality float hashing in coverage build
- remove obsolete MICROPY_FATFS macro
- main: ignore SIGPIPE signal, instead make EPIPE arrive
- main: don't allow to specify too small heap size
- main: implement -m option for packages
- Makefile: enable frozen bytecode modules dir
- move upip to frozen bytecode dir
- Makefile: don't add frozen bytecode to minimal build
- add ilistdir in uos module
- use core-provided KeyboardInterrupt exception object

windows port:
- .gitignore: ignore VC.db and VC.opendb files from VS2015
- make msvc project file support any version from VS2013 to VS2017
- bring mpconfigport.h up-to-date with unix port
- README: convert to Markdown
- README: fix some typos and grammar
- README: add a note about stack usage for msvc
- use core-provided KeyboardInterrupt exception object
- msvc: add machine/pin-related sources to build
- msvc: remove directory with generated files when cleaning
- msvc: do not define DEBUG for debug builds
- msvc: rebuild all qstrs when mpconfig headers are modified
- msvc: workaround parser bug in older MSBuild versions

qemu-arm port:
- don't compile tests in "REPL" mode
- mpconfigport.h: enable MICROPY_PY_BUILTINS_POW3 option
- enable machine module and associated tests
- add basic uos module with generic VFS capabilities
- move lexer constructors to within NLR handler block

stmhal port:
- support PortG on STM32L476 and STM32L486
- fix wrong usage of gcc -print-libgcc-file-name
- fix USB HID receive not receiving the first packet
- implement ioctl for USB HID read
- implement SNAK/CNAK mechanism for USB HID receive
- convert to use builtin help function
- enable help('modules') feature
- add default frozen-bytecode directory and link lcd160cr driver
- fix examples in openocd configs to include addresses
- add ability to have filesystem stored on external SPI flash
- boards/STM32L476DISC: use external SPI flash for filesystem
- mpconfigport.h: reorganise the config options into groups
- usbd_msc_storage: use storage functions instead of disk ones
- convert to use VFS sub-system and new ooFatFs component
- fix name of automatically created boot.py
- moduos: remove duplicated chdir
- use LED constants from PYBv4 onwards
- set the FatFs partition number when initialising VFS object
- fix stack pointer initialisation for F411 and F429 boards
- README: add paragraph about building mpy-cross
- on boot, mount all available partitions of the SD card
- main: put /sd directory before /flash in sys.path
- pin: add C-level pin ioctl method
- modmachine: add machine.Signal type
- main: guard init_sdcard_fs with MICROPY_HW_HAS_SDCARD
- pendsv: fill in comments about what the stack contains
- initial implementation of multithreading, currently disabled
- main: use _estack value to initialise stack extents
- fix build issue when MICROPY_PY_THREAD is disabled
- mpconfigport.h: enable MICROPY_PY_BUILTINS_POW3 option
- on HardFault, print stack pointer and do a stack dump
- add pyb.fault_debug() function, to control hard-fault behaviour
- use MICROPY_EVENT_POLL_HOOK instead of __WFI where appropriate
- add ability to skip booting from SD card via /flash/SKIPSD file
- Makefile: drop use of -mabi=aapcs-linux; link libgcc by default
- boards: for STM32F411DISC, change I2C pin according to datasheet
- implement a proper thread scheduler
- use generic interrupt char code
- main: remove unnecessary header includes
- use mp_hal_delay_ms instead of HAL_Delay
- rename sys_tick ticks/delay functions to corresp. mp_hal ones
- modpyb: use utime ticks ms/us functions instead of custom ones
- modnwcc3k: add include for mp_hal_delay_ms
- mphalport: get ticks_cpu() working on F7 MCUs
- main: allocate flash's VFS struct on the heap to trace root ptrs
- enable micropython.schedule()
- pendsv: disable interrupts during a thread switch
- irq: shift IRQ priorities of TIM and EXTINT to be above PENDSV
- pybthread: allow interrupts to work during lock/unlock of mutex
- systick: make mp_hal_delay_ms release the GIL when sleeping
- boards: fix alt-func config for PA5 of STM32F767
- board: fix existing and add more pin defs for NUCLEO_F767ZI
- spi: clean and/or invalidate D-cache before SPI DMA transfers
- hal: for F7 MCUs, expose DMA_CalcBaseAndBitshift function
- dma: fix reinitialisation of DMA on F7 MCUs, following F4
- update to use size_t for tuple/list accessors
- update for changes to mp_obj_str_get_data
- spi: increase SPI transfer timeout, proportional to num bytes
- support SDMMC alternate functions in pin generation
- sdcard: add support for SDMMC2 on F7 MCUs
- boards: update F76x alternate function table to add SDMMC2
- boards/STM32F769DISC: get SD card working by using SDMMC2
- boards/STM32F769DISC: fix user switch pin, and document stlink
- boards: remove F769 alt function table, it's same as for F767
- dma: don't include SDMMC2 struct if SDMMC2 is not available
- move L4/F7 I2C timing constants from mpconfigboard.h to i2c.c
- i2c: clean the cache so that I2C DMA works on F7 MCUs
- usbd_cdc_interface: increase in-endpoint timeout to 500ms
- usbd_cdc_interface: change CDC RX to use a circular buffer
- enable parsing of all Pin constructor args by machine.Signal
- timer: clear interrupt flag before setting callback
- convert all module and method tables to use MP_ROM macros
- modmachine: add machine.UART class, linking to pyb.UART
- modmachine: remove TODO comment that is now implemented
- add machine.Pin on/off methods
- add ilistdir in uos module

cc3200 port:
- convert to use builtin help function
- add implementations of mp_import_stat and builtin_open
- modusocket: remove deprecated socket.error
- convert to use new VFS sub-system and new ooFatFs library
- refactor "ticks" functions to use common extmod implementation
- move stoupper to ftp.c and define in terms of unichar_toupper
- use simplelink API instead of emulated BSD API
- remove util/std.h, can just use stdio.h instead
- mods/modwlan: remove unused header includes; simplify others
- mods/modwlan: make multi-threaded a proper compile-time option
- mods/modwlan: allow antenna diversity to be fully compiled out
- mods/modwlan: add int casts to silence compiler warnings
- remove remaining references to std.h
- move wlan socket glue functions from modwlan to modusocket
- convert to using uPy internal errno numbers
- when raising OSError's use MP_Exxx as arg instead of a string
- enable uerrno module with short, custom list of error codes
- mods/modusocket: init vars to 0 to silence compiler warnings
- remove socket.timeout class, use OSError(ETIMEDOUT) instead
- moduos: remove uos.sep, as it's strictly optional
- mptask: allocate flash VFS struct on the heap to trace root ptrs
- mods/modutime: use generic sleep_ms and sleep_us implementations
- update to use size_t for tuple/list accessors
- update for changes to mp_obj_str_get_data
- mods/pybi2c: raise OSError if readfrom_mem fails to write addr
- modmachine: return frequency value directly, like other ports
- pybuart: make parity specifications consistent with HW API
- mods/pybi2c: make machine.I2C constructor/init conform to HW API
- mods/pybi2c: make readfnom_mem_into/writeto_mem return None
- mods/pybpin: remove toggle() method

teensy port:
- convert to use builtin help function
- main: remove unnecessary header includes
- lexerfrozen: make mp_lexer_new_from_file raise an exception

esp8266 port:
- convert to use builtin help function
- factor out common linker code to esp8266_common.ld
- switch to use OO version of FatFs library
- change to use new generic VFS sub-system
- fatfs_port: include new oofatfs header
- machine_pin: implement pin ioctl protocol
- modmachine: add Signal class
- mpconfigport.h: remove obsolete MICROPY_FATFS_VOLUMES config
- uart: add support for polling uart device
- moduos: populate release field of uname in case it was GC'd
- mpconfigport.h: enable help('modules') feature
- update lexer constructors so they can raise exceptions
- only execute main.py if in friendly REPL mode
- enable micropython.schedule() with locking in pin callback
- change machine.Timer callback to soft callback
- machine_pin: add "hard" parameter to pin.irq, soft by default
- machine_pin: make pin.irq arguments positional
- machine_pin: fix memset size for zeroing of pin_irq_is_hard
- machine_pin: fix pin.irq() to work when all args are keywords
- modesp: use mp_obj_str_get_str instead of mp_obj_str_get_data
- modesp: remove long-obsolete and unused espconn bindings
- update to use size_t for tuple/list accessors
- update for changes to mp_obj_str_get_data
- remove unused entry in port root pointers
- README: replace reference of alpha status to beta status
- README: add notice about 512K version
- change default settings to mount flash at root dir
- esp8266.ld, esp8266_ota.ld: grow main firmware size by 32KB
- modesp: flash_user_start: Use value from linker script
- modules/flashbdev: reserve one sector for native code storage
- scripts: move drivers/modules to modules/ (frozen bytecode)
- scripts: move initsetup & port_diag tools to modules/
- ets_alt_task.c: prevent spurious large increment of ticks_ms()
- modnetwork: in connect, fix potential buffer overflows
- machine_uart: add uart.any() method
- modules: mount filesystem at root when creating for first time
- mpconfigport.h: remove duplicate link to lwip module
- rename machine.Pin high/low methods to on/off
- add ilistdir in uos module

zephyr port:
- help: update n_args param type to size_t
- remove deprecated .mdef file
- add separate Zephyr config for "minimal" build
- enable SLIP networking for the default build
- convert to use builtin help function
- make sure that correct Zephyr config is used for "minimal" build
- allow to have per-board Zephyr config fragments
- prj_frdm_k64f.conf: add, enable Ethernet support
- Makefile.zephyr: support and default to networked (SLIP) QEMU
- README: describe many gotchas of networked builds
- enable IPv6 networking in addition to IPv4
- add qemu_cortex_m3 config fragment
- main: don't unconditionally dump stats on each GC
- README: network startup issues with frdm_k64f resolved
- modzephyr: add a module for Zephyr-specific things
- modzephyr: fix typo in identifier
- make sure that generated prj.conf is updated only on content changes
- move "minimal" configuration building to a separate wrapper script
- main: nlr_jump_fail: Fix noreturn warning
- main: remove unused __fatal_error()
- main: move lexer constructor to within NLR handler block
- zephyr_getchar: use native k_sem instead of legacy nano_sem
- prj_base.conf: disable legacy kernel compatibility
- prj_base.conf: enable TCP (and UDP explicitly)
- Makefile: rework to use modern, official build integration
- Makefile: add workaround (fix?) for broken builds for DTS targets
- fix NLR segfault in minimal build
- modusocket: initial version of usocket module for Zephyr
- integrate modusocket into build
- modusocket: implement bind() and connect()
- modusocket: implement send()
- modusocket: implement recv() for UDP sockets
- modusocket: implement recv() for TCP sockets
- prj_base.conf: add config for net_buf logging
- modusocket: be sure to use MP_OBJ_FROM_PTR
- modusocket: factor out socket_new() function
- zephyr_getchar: explicitly yield to other threads on char availability
- Makefile: add "test" target, runs testsuite in QEMU
- modusocket: factor out "extended k_fifo API"
- modusocket: implement listen()
- modusocket: socket_bind: Don't set recv callback on STREAM sockets
- modusocket: implement accept()
- mpconfigport.h: fix build if usocket module is disabled
- modmachine: add Signal class
- machine_pin: implement pin protocol for machine.Signal support
- modusocket: call net_nbuf_print_frags() in recv callback if DEBUG > 1
- modusocket: strip packet header right in the receive callback
- modmachine: implement machine.reset()
- main: configure IPv4 netmask and gateway to allow Internet access
- add 96b_carbon configuration
- modusocket: refactor send() into stream write() method
- modusocket: enable stream write() method
- modusocket: refactor recv() into stream read() method
- modusocket: add read/readline/readinto stream methods
- modusocket: sock_read: Check socket status only at the start of packet
- modusocket: add dummy makefile() implementation
- Makefile: add debugserver Zephyr target
- mpconfigport.h: enable line number information for scripts
- main: remove superfluous include
- modusocket: add dummy setsockopt() implementation
- modusocket: add SOL_SOCKET and SO_REUSEADDR constants
- prj_qemu_x86.conf: bump RAM size to 320K
- README: update to require Zephyr 1.8
- modusocket: wrap pkt_get_info() call
- modusocket: update for net_pkt refactor
- modusocket: switch to net_pkt_append() returning length
- modusocket: if there're no packets in recv_q, cancel waiter
- modusocket: implement getaddrinfo()
- modusocket: first step to switch to alternative FIFO processing
- modusocket: get rid of cur_pkt object member
- main: check default netif before applying operations to it
- modusocket: getaddrinfo: Use RAISE_ERRNO for proper error decoding
- modusocket: getaddrinfo: Raise OSError on resolution timeout, etc
- modusocket: use DEBUG_PRINT macro name as other modules do
- rename machine.Pin high/low methods to on/off
- don't send more than MTU allows
- modusocket: handle a case when recv_q is empty when EOF is signaled

pic16bit port:
- main: make nlr_jump_fail never return
- main: make mp_lexer_new_from_file raise an exception

README:
- explicitly mention "await" support, and formatting for keywords
- add link to docs.micropython.org
- describe extmod/ dir
- change Travis & Coveralls badges to not use link references

travis:
- unconditionally run coveralls analysis, even if others failed
- change an stmhal rule to build PYBV11 instead of default PYBV10

gitattributes:
- add .mpy files to list of binary files
- remove obsolete lines

docs:
- fix some minor spelling mistakes
- add documentation for lcd160cr module
- pyboard/tutorial: add tutorial for LCD160CR
- library/lcd160cr: fix set_brightness range, should be 0..31
- machine.Timer: move WiPy adhoc parts to its documentation
- machine: add explicit note on machine module level and scope
- usocket: clarify exceptions used
- usocket: elaborate "Constants" section
- usocket: clarify description of various methods
- usocket: dedent Methods section
- uio: describe differences between uPy an CPy stream hierarchy
- conf.py: add myself as a copyright holder on the docs
- uio: typo fixes/lexical improvements
- pyboard/tutorial/lcd160cr_skin: fix typo, get_touched->get_touch
- for LCD160CR driver and tutorial, add link to positioning image
- esp8266/tutorial: specify the baudrate in picocom example command
- add M-logo as favicon
- library/pyb.Pin: minor typo fix, B6 should be A0
- library/machine: make separate TOC for WiPy vs non-WiPy
- uos: remove mention of uos.sep
- library/lcd160cr: mention the valid values for set_power() method
- modify Makefile and indexes to generate cPy-differences pages
- uhashlib: provide port-neutral description
- Makefile: define and use PYTHON as the interpreter for CPYDIFF
- machine: fix formatting of Constants section
- library/lcd160cr: add note about supported JPEG format/encodings
- library: add framebuf documentation
- library/lcd160cr: add link to framebuf page
- esp8266/tutorial: update since esptool 1.3 added Python 3 support
- library/framebuf: fix typo in bit-width for MVLSB description
- library/machine.I2C: fix scan() doc to match implementation
- library/btree: add btree module docs
- utime: de-conditionalize description of sleep_ms() and friends
- uos: de-conditionalize statvfs() description
- machine.SPI: remove outdated wipy chunk
- machine.Pin: move wipy-specific details to its own docs
- machine.Pin: move wipy-specific methods to its docs
- esp8266/general: start explicit "Known Issues", mentioned RTC inaccuracy
- library/builtins: int: Add notice on byteorder param for to/from_bytes
- library/machine.UART: remove some conditionals
- utime: deconditionalize description of sleep()
- usocket: deconditionalize
- uhashlib: deconditionalize
- esp8266/tutorial/intro: reword section on flash size requirement
- library/micropython: deconditionalize
- library/uos: urandom: Generalize description
- library/ussl: deconditionalize, wipy notes moved to its documentation
- machine.UART: deconditionalize normal methods
- machine: move machine.main() misnomer to wipy's known issues
- library/machine: typo fix in machine_callbacks section
- library/machine.UART: remove pyboard-specific section
- wipy/quickref: update reference for change to I2C API
- wipy/general: add section about specifics of I2C implementation
- library/machine.I2C: deconditionalise all methods
- library/machine.*: add cross-reference label to individual classes
- esp8266/quickref: add links from quickref page to machine classes
- library/machine.I2C: remove WiPy-specific return values
- library/machine.SPI: fix formatting of bullet list to stop warning
- library/uos: add description of uos.ilistdir() function
- machine.Pin: there's no toggle() method in MicroPython hardware API
- machine.Signal: add initial draft description of Signal class
- library/index: add important summary of the intro section as warning
- change single occurrence of "Micropython" to "MicroPython"
- library/micropython: document the newer micropython functions
- library/machine.UART: update and improve uart.any() docs
- library/machine.Pin: remove .id() method and .board class attr

examples:
- hwapi: use Signal for inverted LED on ESP-12
- hwapi: consistently use Signal class to define LEDs
- button_reaction: update for time_pulse_us() no longer raising exc
- hwapi: add hwconfig_pyboard.py for pyboard
- hwapi: be sure to import Signal when it's used
- hwapi/soft_pwm: use Signal on()/off() methods
- embedding/README: convert to markdown, grammar and clarity fixes
- embedding: place lexer constructor within NLR handler block
- hwapi: add config for Zephyr port of 96Boards Carbon
- hwapi/hwconfig*: use inline Signal() args where possible
- hwapi/soft_pwm2_uasyncio: update for call_later_ms()

Support for Xtensa emitter and assembler, and upgraded F4 and F7 STM HAL

This release adds support for the Xtensa architecture as a target for the
native emitter, as well as Xtensa inline assembler.  The int.from_bytes
and int.to_bytes methods now require a second argument (the byte order)
per CPython (only "little" is supported at this time).  The "readall"
method has been removed from all stream classes that used it; "read" with
no arguments should be used instead.  There is now support for importing
packages from compiled .mpy files.  Test coverage is increased to 96%.

The generic I2C driver has improvements: configurable clock stretching
timeout, "stop" argument added to readfrom/writeto methods, "nack"
argument added to readinto, and write[to] now returns num of ACKs
received.  The framebuf module now handles 16-bit depth (generic colour
format) and has hline, vline, rect, line methods.  A new utimeq module is
added for efficient queue ordering defined by modulo time (to be
compatible with time.ticks_xxx functions).  The pyboard.py script has been
modified so that the target board is not reset between scripts or commands
that are given on a single command line.

For the stmhal port the STM Cube HAL has been upgraded: Cube F4 HAL to
v1.13.1 (CMSIS 2.5.1, HAL v1.5.2) and Cube F7 HAL to v1.1.2.  There is a
more robust pyb.I2C implementation (DMA is now disabled by default, can be
enabled via an option), and there is an implementation of machine.I2C with
robust error handling and hardware acceleration on F4 MCUs.  It is now
recommended to use machine.I2C instead of pyb.I2C.  The UART class is now
more robust with better handling of errors/timeouts.  There is also more
accurate VBAT and VREFINT measurements for the ADC.  New boards that are
supported include: NUCLEO_F767ZI, STM32F769DISC and NUCLEO_L476RG.

For the esp8266 port select/poll is now supported for sockets using the
uselect module.  There is support for native and viper emitters, as well
as an inline assembler (with limited iRAM for storage of native functions,
or the option to store code to flash).  There is improved software I2C
with a slight API change: scl/sda pins can be specified as positional only
when "-1" is passed as the first argument to indicate the use of software
I2C.  It is recommended to use keyword arguments for scl/sda.  There is
very early support for over-the-air (OTA) updates using the yaota8266
project.

A detailed list of changes follows.

py core:
- emitnative: fix native import emitter when in viper mode
- remove readall() method, which is equivalent to read() w/o args
- objexcept: allow clearing traceback with 'exc.__traceback__ = None'
- runtime: mp_resume: handle exceptions in Python __next__()
- mkrules.mk: rework find command so it works on OSX
- *.mk: replace uses of 'sed' with $(SED)
- parse: move function to check for const parse node to parse.[ch]
- parse: make mp_parse_node_new_leaf an inline function
- parse: add code to fold logical constants in or/and/not operations
- factor persistent code load/save funcs into persistentcode.[ch]
- factor out persistent-code reader into separate files
- lexer: rewrite mp_lexer_new_from_str_len in terms of mp_reader_mem
- lexer: provide generic mp_lexer_new_from_file based on mp_reader
- lexer: rewrite mp_lexer_new_from_fd in terms of mp_reader
- lexer: make lexer use an mp_reader as its source
- objtype: implement __call__ handling for an instance w/o heap alloc
- factor out common code from assemblers into asmbase.[ch]
- stream: move ad-hoc ioctl constants to stream.h and rename them
- compile: simplify configuration of native emitter
- emit.h: remove long-obsolete declarations for cpython emitter
- move arch-specific assembler macros from emitnative to asmXXX.h
- asmbase: add MP_PLAT_COMMIT_EXEC option for handling exec code
- asmxtensa: add low-level Xtensa assembler
- integrate Xtensa assembler into native emitter
- allow inline-assembler emitter to be generic
- add inline Xtensa assembler
- emitinline: embed entire asm struct instead of a pointer to it
- emitinline: move inline-asm align and data methods to compiler
- emitinline: move common code for end of final pass to compiler
- asm: remove need for dummy_data when doing initial assembler passes
- objint: from_bytes, to_bytes: require byteorder arg, require "little"
- binary: do zero extension when storing a value larger than word size
- builtinimport: support importing packages from compiled .mpy files
- mpz: remove unreachable code in mpn_or_neg functions
- runtime: zero out fs_user_mount array in mp_init
- mpconfig.h: enable MICROPY_PY_SYS_EXIT by default
- add MICROPY_KBD_EXCEPTION config option to provide mp_kbd_exception
- compile: add an extra pass for Xtensa inline assembler
- modbuiltins: remove unreachable code
- objint: rename mp_obj_int_as_float to mp_obj_int_as_float_impl
- emitglue: refactor to remove assert(0), to improve coverage
- lexer: remove unreachable code in string tokeniser
- lexer: remove unnecessary check for EOF in lexer's next_char func
- lexer: permanently disable the mp_lexer_show_token function
- parsenum: simplify and generalise decoding of digit values
- mpz: fix assertion in mpz_set_from_str which checks value of base
- mpprint: add assertion for, and comment about, valid base values
- objint: simplify mp_int_format_size and remove unreachable code
- unicode: comment-out unused function unichar_isprint
- consistently update signatures of .make_new and .call methods
- mkrules.mk: add MPY_CROSS_FLAGS option to pass flags to mpy-cross
- builtinimport: fix bug when importing names from frozen packages

extmod:
- machine_i2c: make the clock stretching timeout configurable
- machine_i2c: raise an error when clock stretching times out
- machine_i2c: release SDA on bus error
- machine_i2c: add a C-level I2C-protocol, refactoring soft I2C
- machine_i2c: add argument to C funcs to control stop generation
- machine_i2c: rewrite i2c.scan in terms of C-level protocol
- machine_i2c: rewrite mem xfer funcs in terms of C-level protocol
- machine_i2c: remove unneeded i2c_write_mem/i2c_read_mem funcs
- machine_i2c: make C-level functions return -errno on I2C error
- machine_i2c: add 'nack' argument to i2c.readinto
- machine_i2c: make i2c.write[to] methods return num of ACKs recvd
- machine_i2c: add 'stop' argument to i2c readfrom/writeto meths
- machine_i2c: remove trivial function wrappers
- machine_i2c: expose soft I2C obj and readfrom/writeto funcs
- machine_i2c: add hook to constructor to call port-specific code
- modurandom: allow to build with float disabled
- modframebuf: make FrameBuffer handle 16bit depth
- modframebuf: add back legacy FrameBuffer1 "class"
- modframebuf: optimise fill and fill_rect methods
- vfs_fat: implement POSIX behaviour of rename, allow to overwrite
- moduselect: use stream helper function instead of ad-hoc code
- moduselect: use configurable EVENT_POLL_HOOK instead of WFI
- modlwip: add ioctl method to socket, with poll implementation
- vfs_fat_file: allow file obj to respond to ioctl flush request
- modbtree: add method to sync the database
- modbtree: rename "sync" method to "flush" for consistency
- modframebuf: add hline, vline, rect and line methods
- machine_spi: provide reusable software SPI class
- modframebuf: make framebuf implement the buffer protocol
- modframebuf: store underlying buffer object to prevent GC free
- modutimeq: copy of current moduheapq with timeq support for refactoring
- modutimeq: refactor into optimized class
- modutimeq: make time_less_than be actually "less than", not less/eq

lib:
- utils/interrupt_char: use core-provided mp_kbd_exception if enabled

drivers:
- display/ssd1306.py: update to use FrameBuffer not FrameBuffer1
- onewire: enable pull up on data pin
- onewire/ds18x20: fix negative temperature calc for DS18B20

tools:
- tinytest-codegen: blacklist recently added uheapq_timeq test (qemu-arm)
- pyboard.py: refactor so target is not reset between scripts/cmd
- mpy-tool.py: add support for OPT_CACHE_MAP_LOOKUP_IN_BYTECODE

tests:
- micropython: add test for import from within viper function
- use read() instead of readall()
- basics: add test for logical constant folding
- micropython: add test for creating traceback without allocation
- micropython: move alloc-less traceback test to separate test file
- extmod: improve ujson coverage
- basics: improve user class coverage
- basics: add test for dict.fromkeys where arg is a generator
- basics: add tests for if-expressions
- basics: change dict_fromkeys test so it doesn't use generators
- basics: enable tests for list slice getting with 3rd arg
- extmod/vfs_fat_fileio: add test for constructor of FileIO type
- extmod/btree1: exercise btree.flush()
- extmod/framebuf1: add basics tests for hline, vline, rect, line
- update for required byteorder arg for int.from_bytes()/to_bytes()
- extmod: improve moductypes test coverage
- extmod: improve modframebuf test coverage
- micropython: get heapalloc_traceback test running on baremetal
- struct*: make skippable
- basics: improve mpz test coverage
- float/builtin_float_round: test round() with second arg
- basics/builtin_dir: add test for dir() of a type
- basics: add test for builtin locals()
- basics/set_pop: improve coverage of set functions
- run-tests: for REPL tests make sure the REPL is exited at the end
- basics: improve test coverage for generators
- import: add a test which uses ... in from-import statement
- add tests to improve coverage of runtime.c
- add tests to improve coverage of objarray.c
- extmod: add test for utimeq module
- basics/lexer: add a test for newline-escaping within a string
- add a coverage test for printing the parse-tree
- utimeq_stable: test for partial stability of utimeq queuing
- heapalloc_inst_call: test for no alloc for simple object calls
- basics: add tests for parsing of ints with base 36
- basics: add tests to improve coverage of binary.c
- micropython: add test for micropython.stack_use() function
- extmod: improve ubinascii.c test coverage
- thread: improve modthread.c test coverage
- cmdline: improve repl.c autocomplete test coverage
- unix: improve runtime_utils.c test coverage
- pyb/uart: update test to match recent change to UART timeout_char
- run-tests: allow to skip set tests
- improve warning.c test coverage
- float: improve formatfloat.c test coverage using Python
- unix: improve formatfloat.c test coverage using C
- unix/extra_coverage: add basic tests to import frozen str and mpy
- types1: split out set type test to set_types
- array: allow to skip test if "array" is unavailable
- unix/extra_coverage: add tests for importing frozen packages

unix port:
- rename define for unix moduselect to MICROPY_PY_USELECT_POSIX
- Makefile: update freedos target for change of USELECT config name
- enable utimeq module
- main: allow to print the parse tree in coverage build
- Makefile: make "coverage_test" target mirror Travis test actions
- moduselect: if file object passed to .register(), return it in .poll()
- Makefile: split long line for coverage target, easier to modify
- enable and add basic frozen str and frozen mpy in coverage build
- Makefile: allow cache-map-lookup optimisation with frozen bytecode

windows port:
- enable READER_POSIX to get access to lexer_new_from_file

stmhal port:
- dma: de-init the DMA peripheral properly before initialising
- i2c: add option to I2C to enable/disable use of DMA transfers
- i2c: reset the I2C peripheral if there was an error on the bus
- rename mp_hal_pin_set_af to _config_alt, to simplify alt config
- upgrade to STM32CubeF4 v1.13.0 - CMSIS/Device 2.5.1
- upgrade to STM32CubeF4 v1.13.0 - HAL v1.5.1
- apply STM32CubeF4 v1.13.1 patch - upgrade HAL driver to v1.5.2
- hal/i2c: reapply HAL commit ea040a4 for f4
- hal/sd: reapply HAL commit 1d7fb82 for f4
- hal: reapply HAL commit 9db719b for f4
- hal/rcc: reapply HAL commit c568a2b for f4
- hal/sd: reapply HAL commit 09de030 for f4
- boards: configure all F4 boards to work with new HAL
- make-stmconst.py: fix regex's to work with current CMSIS
- i2c: handle I2C IRQs
- dma: precalculate register base and bitshift on handle init
- dma: mark DMA sate as READY even if HAL_DMA_Init is skipped
- can: clear FIFO flags in IRQ handler
- i2c: provide custom IRQ handlers
- hal: do not include <stdio.h> in HAL headers
- mphalport.h: use single GPIOx->BSRR register
- make-stmconst.py: add support for files with invalid utf8 bytes
- update HALCOMMITS due to change to hal
- make-stmconst.py: restore Python 2 compatibility
- update HALCOMMITS due to change to hal
- moduselect: move to extmod/ for reuse by other ports
- i2c: use the HAL's I2C IRQ handler for F7 and L4 MCUs
- updates to get F411 MCUs compiling with latest ST HAL
- i2c: remove use of legacy I2C_NOSTRETCH_DISABLED option
- add beginnings of port-specific machine.I2C implementation
- i2c: add support for I2C4 hardware block on F7 MCUs
- i2c: expose the pyb_i2c_obj_t struct and some relevant functions
- machine_i2c: provide HW implementation of I2C peripherals for F4
- add support for flash storage on STM32F415
- add back GPIO_BSRRL and GPIO_BSRRH constants to stm module
- add OpenOCD configuration for STM32L4
- add address parameters to openocd config files
- adc: add "mask" selection parameter to pyb.ADCAll constructor
- adc: provide more accurate measure of VBAT and VREFINT
- adc: make ADCAll.read_core_temp return accurate float value
- adc: add ADCAll.read_vref method, returning "3.3v" value
- adc: add support for F767 MCU
- adc: make channel "16" always map to the temperature sensor
- sdcard: clean/invalidate cache before DMA transfers with SD card
- moduos: implement POSIX behaviour of rename, allow to overwrite
- adc: use constants from new HAL version
- refactor UART configuration to use pin objects
- uart: add support for UART7 and UART8 on F7 MCUs
- uart: add check that UART id is valid for the given board
- cmsis: update STM32F7 CMSIS device include files to V1.1.2
- hal: update ST32CubeF7 HAL files to V1.1.2
- port of f4 hal commit c568a2b to updated f7 hal
- port of f4 hal commit 09de030 to updated f7 hal
- port of f4 hal commit 1d7fb82 to updated f7 hal
- declare and initialise PrescTables for F7 MCUs
- boards/STM32F7DISC: define LSE_STARTUP_TIMEOUT
- hal: update HALCOMMITS due to change in f7 hal files
- refactor to use extmod implementation of software SPI class
- cmsis: add CMSIS file stm32f767xx.h, V1.1.2
- add NUCLEO_F767ZI board, with openocd config for stm32f7
- cmsis: add CMSIS file stm32f769xx.h, V1.1.2
- add STM32F769DISC board files
- move PY_SYS_PLATFORM config from board to general config file
- mpconfigport: add weak-module links for io, collections, random
- rename mp_const_vcp_interrupt to mp_kbd_exception
- usb: always use the mp_kbd_exception object for VCP interrupt
- use core-provided keyboard exception object
- led: properly initialise timer handle to zero before using it
- mphalport.h: explicitly use HAL's GPIO constants for pull modes
- usrsw: use mp_hal_pin_config function instead of HAL_GPIO_Init
- led: use mp_hal_pin_config function instead of HAL_GPIO_Init
- sdcard: use mp_hal_pin_config function instead of HAL_GPIO_Init
- add support for STM32 Nucleo64 L476RG
- uart: provide a custom function to transmit over UART
- uart: increase inter-character timeout by 1ms
- enable utimeq module

cc3200 port:
- tools/smoke.py: change readall() to read()
- pybspi: remove static mode=SPI.MASTER parameter for latest HW API
- mods/pybspi: remove SPI.MASTER constant, it's no longer needed
- update for moduselect moved to extmod/
- re-add support for UART REPL (MICROPY_STDIO_UART setting)
- enable UART REPL by default
- README: (re)add information about accessing REPL on serial
- make: rename "deploy" target to "deploy-ota"
- add targets to erase flash, deploy firmware using cc3200tool
- README: reorganize and update to the current state of affairs
- modwlan: add network.WLAN.print_ver() diagnostic function

esp8266 port:
- enable uselect module
- move websocket_helper.py from scripts to modules for frozen BC
- refactor to use extmod implementation of software SPI class
- mpconfigport_512k: disable framebuf module for 512k build
- enable native emitter for Xtensa arch
- enable inline Xtensa assembler
- add "ota" target to produce firmware binary for use with yaota8266
- use core-provided keyboard exception object
- add "erase" target to Makefile, to erase entire flash
- when doing GC be sure to trace the memory holding native code
- modesp: flash_user_start(): support configuration with yaota8266
- force relinking OTA firmware image if built after normal one
- scripts/inisetup: dump FS starting sector/size on error
- Makefile: produce OTA firmware as firmware-ota.bin
- modesp: make check_fw() work with OTA firmware
- enable utimeq module
- Makefile: put firmware-ota.bin in build/, for consistency
- modules/flashbdev: add RESERVED_SECS before the filesystem
- modules/flashbdev: remove code to patch bootloader flash size
- modules/flashbdev: remove now-unused function set_bl_flash_size
- modules/flashbdev: change RESERVED_SECS to 0

zephyr port:
- add .gitignore to ignore Zephyr's "outdir" directory
- zephyr_getchar: update to Zephyr 1.6 unified kernel API
- switch to Zephyr 1.6 unified kernel API
- support raw REPL
- implement soft reset feature
- main: initialize sys.path and sys.argv
- use core-provided keyboard exception object
- uart_core: access console UART directly instead of printk() hack
- enable slice subscription

docs:
- remove references to readall() and update stream read() docs
- library/index: elaborate on u-modules
- library/machine.I2C: refine definitions of I2C methods
- library/pyb.Accel: add hardware note about pins used by accel
- library/pyb.UART: added clarification about timeouts
- library/pyb.UART: moved writechar doc to sit with other writes
- esp8266/tutorial: update intro to add Getting the firmware section
- library/machine.I2C: fix I2C constructor docs to match impl
- esp8266/tutorial: close socket after reading page content
- esp8266/general: add "Scarcity of runtime resources" section
- library/esp: document esp.set_native_code_location() function
- library/esp: remove para and add further warning about flash
- usocket: clarify that socket timeout raises OSError exception

travis:
- build STM32 F7 and L4 boards under Travis CI
- include persistent bytecode with floats in coverage tests

examples:
- hwapi: button_led: Add GPIO pin read example
- hwapi: add soft_pwm example converted to uasyncio
- http_client: use read() instead of readall()
- hwapi: add uasyncio example of fading 2 LEDs in parallel
- hwapi: add example for machine.time_pulse_us()
- hwapi: add hwconfig for console tracing of LED operations
- accellog.py: change 1: to /sd/, and update comment about FS
- hwapi/hwconfig_console: don't alloc memory in value()

ESP8266 port uses SDK 2.0, has more heap, has support for 512k devices

This release brings some code size reductions to the core as well as
more tests and improved coverage which is now at 94.3%.

The time.ticks_diff(a, b) function has changed: the order of the arguments
has been swapped so that it behaves like "a - b", and it can now return a
negative number if "a" came before "b" (modulo the period of the ticks
functions).

For the ESP8266 port the Espressif SDK has been updated to 2.0.0, the
heap has been increased from 28k to 36k, and there is support for 512k
devices via "make 512k".  upip is included by default as frozen bytecode.
The network module now allows access-point reconnection without WiFi
credentials, and exposes configuration for the station DHCP hostname.  The
DS18B20 driver now handles negative temperatures, and NeoPixel and APA102
drivers handle 4 bytes-per-pixel LEDs.

For the CC3200 port there is now support for loading of precompiled .mpy
files and threading now works properly with interrupts.

A detailed list of changes follows.

py core:
- py.mk: automatically add frozen.c to source list if FROZEN_DIR is defined
- be more specific with MP_DECLARE_CONST_FUN_OBJ macros
- specialise builtin funcs to use separate type for fixed arg count
- {modbuiltins,obj}: use MP_PYTHON_PRINTER where possible
- modbuiltins: add builtin "slice", pointing to existing slice type
- add "delattr" builtin, conditional on MICROPY_CPYTHON_COMPAT
- sequence: fix reverse slicing of lists
- fix null pointer dereference in mpz.c, fix missing va_end in warning.c
- remove asserts that are always true in emitbc.c
- fix wrong assumption that m_renew will not move if shrinking
- change config default so m_malloc0 uses memset if GC not enabled
- add MICROPY_FLOAT_CONST macro for defining float constants
- move frozen bytecode Makefile rules from ports to common mk files
- strip leading dirs from frozen mpy files, so any path can be used

extmod:
- vfs_fat_file: check fatfs f_sync() and f_close() returns for errors
- vfs_fat_file: make file.close() a no-op if file already closed
- utime_mphal: ticks_diff(): switch arg order, return signed value
- utime_mphal: add MP_THREAD_GIL_EXIT/ENTER warppers for sleep functions
- utime_mphal: implement ticks_add(), add to all maintained ports
- utime_mphal: allow ticks functions period be configurable by a port

lib:
- utils/pyhelp.c: use mp_printf() instead of printf()
- utils/pyexec: add mp_hal_set_interrupt_char() prototype
- libm: move Thumb-specific sqrtf function to separate file

drivers:
- add "from micropython import const" when const is used

tools:
- upgrade upip to 1.1.4: fix error on unix when installing to non-existing
  absolute path
- pip-micropython: remove deprecated wrapper tool
- check_code_size.sh: code size validation script for CI
- replace upip tarball with just source file, to make its inclusion as
  frozen modules in multiple ports less magic

tests:
- extmod/vfs_fat: improve VFS test coverage
- basics/builtin_slice: add test for "slice" builtin name
- basics: add test for builtin "delattr"
- extmod/vfs_fat_fsusermount: improve fsusermount test coverage
- extmod/vfs_fat_oldproto: test old block device protocol
- basics/gc1: garbage collector threshold() coverage
- extmod/uhashlib_sha1: coverage for SHA1 algorithm
- extmod/uhashlib_sha256: rename sha256.py test
- btree1: fix out of memory error running on esp8266
- extmod/ticks_diff: test for new semantics of ticks_diff()
- extmod/framebuf1: test framebuffer pixel clear, and text function

minimal port:
- Makefile: split rule for firmware.bin generation

unix port:
- Makefile: remove references to deprecated pip-micropython
- modtime: use ticks_diff() implementation from extmod/utime_mphal.c
- mphalport.h: add warning of mp_hal_delay_ms() implementation
- modtime: switch ticks/sleep_ms/us() to utime_mphal
- fix symbol references for x86 Mac
- replace upip tarball with just source file

windows port:
- enable utime_mphal following unix, define mp_hal_ticks_*
- fix utime_mphal compilation for msvc
- implement mp_hal_ticks_cpu in terms of QueryPerformanceCounter

qemu-arm port:
- exclude ticks_diff test for qemu-arm port
- exclude extmod/vfs_fat_fileio.py test
- exclude new vfs_fat tests
- enable software floating point support, and float tests

stmhal port:
- modutime: refactor to use extmod's version of ticks_cpu
- refactor pin usage to use mp_hal_pin API
- led: refactor LED to use mp_hal_pin_output() init function
- Makefile: use standard rules for frozen module generation
- modutime: consistently convert to MP_ROM_QSTR/MP_ROM_PTR
- enable SD power save (disable CLK on idle)

cc3200 port:
- use mp_raise_XXX helper functions to reduce code size
- mods/pybspi: allow "write" arg of read/readinto to be positional
- enable loading of precompiled .mpy files
- fix thread mutex's so threading works with interrupts

teensy port:
- update to provide new mp_hal_pin_XXX functions following stmhal

esp8266 port:
- Makefile: use latest esptool.py flash size auto-detection
- esp_init_data: auto-initialize system params with vendor SDK 2.0.0
- esp8266.ld: move help.o to iROM
- esp8266.ld: move modmachine.o to iROM
- esp8266.ld: move main.o to iROM
- add MP_FASTCODE modifier to put a function to iRAM
- main: mark nlr_jump_fail() as MP_FASTCODE
- modules/webrepl: enforce only one concurrent WebREPL connection
- etshal.h: add few more ESP8266 vendor lib prototypes
- modesp: add flash_user_start() function
- add support for building firmware version for 512K modules
- scripts: make neopixel/apa102 handle 4bpp LEDs with common code
- modutime: consistently convert to MP_ROM_QSTR/MP_ROM_PTR
- modnetwork: config(): fix copy-paste error in setting "mac"
- scripts/port_diag: add descriptions for esf_buf types
- modnetwork.c: allows AP reconnection without WiFi credentials
- main: bump heap size to 36K
- etshal.h: add prototypes for SPIRead/SPIWrite/SPIEraseSector
- etshal.h: adjust size of MD5_CTX structure
- modules: fix negative temperature in ds18x20 driver
- rename "machine" module implementation to use contemporary naming
- rework webrepl_setup to run over wired REPL
- espneopixel.c: solve glitching LED issues with cpu at 80MHz
- include upip as a standard frozen bytecode module
- update docs for esptool 1.2.1/SDK 2.0 (--flash_size=detect)
- modnetwork.c: expose configuration for station DHCP hostname

zephyr port:
- implement utime module
- use board/SoC values for startup banner based on Zephyr config
- initial implementation of machine.Pin
- zephyr_getchar: update for recent Zephyr refactor of console hooks
- support time -> utime module "weaklink"
- README: update for the current featureset, add more info
- mpconfigport.h: move less important params to the bottom
- Makefile: allow to adjust heap size from make command line
- Makefile: update comments to the current state of affairs
- Makefile: allow to override Zephyr config from make command line
- Makefile: add minimal port
- Makefile: add -fomit-frame-pointer to reduce code size
- mphalport.h: update for new "unified" kernal API (sleep functions)

docs:
- machine.SPI: bring up to date with Hardware API, make vendor-neutral
- machine.SPI: improve descriptions of xfer methods
- library/builtins: add docs for delattr and slice
- library/network: reword intro paragraph
- library/network: typo fixes, consistent acronym capitalization
- library/index: update TOCs so builtins sorted before modules
- utime: document ticks_cpu() in more detail
- utime: describe new semantics of ticks_diff() (signed ring arithmetics)
- utime: add docs for ticks_add(), improvements for other ticks_*()
- esp8266: update for new WebREPL setup procedure
- */quickref.rst: use new semantics of ticks_diff()
- library/machine.Pin: update Pin docs to align with new HW API

travis:
- integrate tools/check_code_size.sh
- minimal: Use CROSS=1, for binary size check

examples:
- http_server_simplistic: add "not suitable for real use" note
- hwapi: example showing best practices for HW API usage in apps
- hwapi: add hwconfig for DragonBoard 410c

New port to Zephyr, upip runs on baremetal, and reduction in code size

This release adds a new port of MicroPython to run on top of the Zephyr
real-time operating system.  As part of this there is now basic support for
using mbedTLS as the ussl module.  The release also brings initial support
for running the package manager upip on baremetal systems with low heap
memory (such as esp8266), through a Python module interface.

Work has been done in this release to clean up the core, removing redundant
and/or unreachable code, and factoring existing duplicated code patterns.
This brings a reduction of 828 bytes in code size to the bare-arm port, and
1368 bytes to the minimal port.  There is also improved coverage through
the addition of new tests for corner cases.

The "micropython" module sees the addition of the "const" identity function
which should be used as "from micropython import const" in scripts that
want to use the MicroPython constant optimisations in the compile stage.
There is also the addition of the "opt_level" function to change the
parser/compiler optimisation level at runtime.

The behaviour of "sys.exit" (and "raise SystemExit") on baremetal is now
changed: this function no longer does a soft-reset of the board, rather it
just stops the running script and drops to the REPL.  In order to do an
actual soft reset the "machine.soft_reset" function has been added (to the
stmhal port only, for the time being).

Following CPython, KeyError exceptions for dictionary lookups now have the
failed key stored as the argument of the exception instance, accessible as
exc.args[0].  The "ujson.load" function has also been added, to load JSON
data from an arbitrary stream.

The I2C support in the machine module now has clock stretching, the
addition of the "addrsize" parameter in memory transfer methods, and I2C
scanning now uses dummy writes instead of dummy reads to make the scanning
more reliable.

The CMSIS library has been upgrade to v4.30, and the boards section of
the stmhal port has been refactored to use a common.ld script.  The stmhal
port now has a full implementation of the machine.SPI class, with support
for both hardware SPI peripherals and fast software SPI.  The USB HID
driver in stmhal has added support to receive USB HID messages from the
host.

py core:
- asmthumb: flush D-cache, and invalidate I-cache on STM32F7
- makeqstrdefs.py: use python 2.6 syntax for set creation
- objnone: remove unnecessary handling of MP_UNARY_OP_BOOL
- move frozen modules rules from esp8266 port for reuse across ports
- combine 3 comprehension emit functions (list/dict/set) into 1
- combine 3 comprehension opcodes (list/dict/set) into 1
- vstr: remove vstr.had_error flag and inline basic vstr functions
- objnone: use mp_generic_unary_op instead of custom one
- showbc: make printf's go to the platform print stream
- remove 'name' member from mp_obj_module_t struct
- builtinimport: fix nanbox build after change to better handle -m modules
- stream: remove unnecessary check for NULL return from vstr_extend
- py.mk: suppress some compiler warnings when building berkeley-db
- shrink mp_arg_t struct by using reduced-size integer members
- update opcode format table because 3 opcodes were removed, 1 added
- parse: only replace constants that are standalone identifiers
- py.mk: add support for building modussl_mbedtls
- only store the exception instance on Py stack in bytecode try block
- vm: use MP_OBJ_FROM_PTR to cast a type to an object
- modmicropython: add micropython.const, alias for identity function
- objstr: remove unreachable function used only for terse error msgs
- emitbc: remove/refactor unreachable code, to improve coverage
- objfun: remove unnecessary check for viper fun with 5 or more args
- objfun: use if instead of switch to check return value of VM execute
- objset: use mp_check_self() to check args of set/frozenset methods
- objset: ensure that use of frozenset.update raises an exception
- compile: fix async-for/async-with to work with simpler exc on stack
- scope: use lookup-table to determine a scope's simple name
- scope: shrink scope_t struct by 1 machine word
- scope: factor common code to find locals and close over them
- compile: fix typo when checking for parse-node kind
- argcheck: simplify if-chain so that the last one is the default
- objbool: defer bool's unary op implementation to small int
- objbool: make a slight simplification of bool constructor
- modstruct: remove unreachable code, and add comment about CPy diff
- add mp_raise_OSError(errno) helper function
- objstringio: add readinto() method
- modmicropython: add micropython.opt_level([value]) function
- compile: remove unreachable code
- mpz: in divmod, replace check for rhs!=0 with assert
- mpz: use assert to verify mpz does not have a fixed digit buffer
- factor duplicated function to calculate size of formatted int
- objint: use size_t for arguments that measure bytes/sizes
- compile: remove debugging code for compiler dispatch
- lexer: remove unnecessary code, and unreachable code
- vstr: combine vstr_new_size with vstr_new since they are rarely used
- objdict: fix optimisation for allocating result in fromkeys
- objdict: actually provide the key that failed in KeyError exception
- use mp_raise_msg helper function where appropriate
- add the module specified by -m to sys.modules as '__main__'

extmod:
- modussl_mbedtls: initial implementation of mbedTLS ussl module
- uctypes: allow full 32-bit address range
- modubinascii: fix crc32() function on 32-bit platforms
- modussl_mbedtls: implement key= and cert= args to wrap_socket()
- modussl_mbedtls: use 2-component include paths
- machine_i2c: add clock stretching support
- modussl_mbedtls: add server_hostname param for wrap_socket()
- uzlib: add tinfgzip.c (gzip header parsing) from upstream
- moduzlib: DecompIO: Add support for gzip-formatted streams
- uzlib/: update uzlib to v2.0.3
- vfs_fat: add fat_vfs_statvfs(), reused from stmhal
- machine_i2c: add support for the addrsize parameter in mem xfers
- machine_spi: simplify SPI xfer function to only take one buf len
- machine_spi: factor out software SPI code from esp8266 to extmod
- machine_spi: use delay_half, not baudrate, for internal timing
- machine_spi: add optional support for fast software SPI
- vfs_fat: use mp_raise_OSError helper function
- modlwip: use mp_raise_OSError helper function
- use mp_raise_OSError helper function
- vfs_fat_file: use MP_Exxx errno constants
- uzlib: update to upstream v2.1
- machine_i2c: use writes not reads in i2c.scan()
- vfs_fat: add file and directory checks for remove and rmdir
- modujson: implement ujson.load() to load JSON from a stream
- modujson: fix nanbox build
- utime_mphal: factor out implementations in terms of mp_hal_* for reuse
- utime_mphal: sleep_us/ms(): Don't wait on negative argument
- modussl_mbedtls: add dummy setblocking() method

lib:
- interrupt_char: factor out typical Ctrl+C handling from esp8266 port
- cmsis: move CMSIS headers to lib/
- cmsis: remove CMSIS-DSP headers, they are unused
- cmsis: upgrade CMSIS-CORE to V4.30
- utils/pyexec: don't treat SystemExit as "forced exit"
- utils/pyexec: allow behaviour of SystemExit to be configurable

drivers:
- dht: use mp_raise_OSError helper function

tools:
- update upip to 0.8, fixes IPv6 support
- upgrade upip to 1.0, fully self-hosted release (without fallbacks), and
  uses stream gzip decompression (step towards support for limited-heap
  baremetal systems)
- upgrade upip to 1.1.3, initial support for running on a baremetal,
  low-heap systems (like esp8266), using Python module interface

tests:
- pyb: add test for ExtInt when doing swint while disabled
- pyb: update exp file for previously updated extint test
- extmod/urandom: add urandom tests for error cases
- basics: add errno1 test, to check basics of uerrno module
- extmod: add test for machine.time_pulse_us()
- struct1: test "l" specifier to improve coverage
- array1: add tests for "l", "L" array types to improve coverage
- get cmdline verbose tests running again
- run-tests: add --via-mpy option to run test from precompiled code
- uzlib_decompio_gz: test for DecompIO with gzip bitstream
- basics: add test case for overflowing Py stack in try-finally
- micropython: add tests for const names being replaced in parser
- cmdline/cmd_showbc: fix test now that 1 value is stored on stack
- extmod/vfs_fat_ramdisk: add test for VFS.statvfs()
- float: add test for parsing a float from an empty string
- basics: add test for set.difference_update with arg being itself
- basics: add further tests for nonlocal scoping and closures
- import: add test for compiling "import a.b as c"
- basics: add test constructing a set from a non-trivial expression
- basics: add test for printing OSError when errno is unknown
- run-tests: disable cmdline/cmd_showbc test on Windows
- extmod/btree1: checks for put, seq, string print and unsupported binary op
- fix expected output of verbose cmdline test
- extmod/uzlib: test adaptive huffman tree for tinflate coverage
- improve coverage of struct with test for non-compliant behaviour
- io/write_ext: add description comment
- io/bytesio_ext: add test for readinto()
- micropython: add test for micropython.opt_level() function
- improve test coverage of py/compile.c
- extmod/vfs_fat: test coverage for remove() and rmdir()
- extmod: add test for ujson.load()
- extmod/vfs_fat: replace asserts with prints and expected outputs
- micropython: add tests for heap_lock, and emergency exceptions
- cmdline: improve coverage test for printing bytecode
- improve coverage of array, range, dict, slice, exc, unicode
- add test to print full KeyError exc from failed dict lookup
- run-tests: enable extmod/machine1.py on pyboard

unix port:
- fix build for when MICROPY_PY_SOCKET=0
- modjni: implement subscription for object arrays
- modjni: add array() top-level function to create Java array
- modjni: array(): Support creation of object arrays
- enable btree module for coverage build
- use mp_raise_OSError helper function
- use common RAISE_ERRNO macro from mphalport.h

windows port:
- enable MICROPY_PY_UERRNO

qemu-arm port:
- enable lots of extmods and enable tests for them

stmhal port:
- lcd: de-assert chip select after completing SPI transmission
- {accel,lcd}: use GPIO_{set,clear}_pin
- extint: force 0 to 1 transition on swint()
- boards: add pllvalues.py script to compute PLL values for sysclk
- boards: for OLIMEX_E407, enable UART1 and fix I2C1 mapping
- use attribute to avoid inlining
- put common definitions from linker files to common.ld
- remove STM32CubeF2 HAL files, they are unused/unsupported
- modmachine: fix clearing of reset-cause flags
- add virtual com port support for STM32L476DISC
- remove CMSIS STM32F2xx files, they are unused/unsupported
- spi: simplify spi_transfer function to take only one buf len arg
- mphalport: implement mp_hal_pin_{input,output,write}
- spi: make machine.SPI class conform to correct API
- mphalport: fix mp_hal_pin_write to use correct pin_mask
- spi: use software SPI if no periph id given, even if pins given
- spi: enable use of fast software SPI
- fix linker map for STM32L476 chips
- usbdev: add OUT endpoint to HID interface
- usb: add support to receive USB HID messages from host
- usb: use correct ClassData structure for HID receive
- usb: use real packet size (not maximum) in HID receive
- fix ESPRUINO_PICO by adding ld scripts with correct flash size
- mphalport: change pin obj type to const pointer, to avoid casts
- moduos: implement total-number-of-blocks field in statvfs
- disable network and usocket for ESPRUINO_PICO
- enable machine.time_pulse_us() function
- use mp_raise_OSError helper function
- pybstdio: use size_t instead of mp_uint_t
- modutime: refactor to use extmod/utime_mphal.c
- implement machine.soft_reset()
- enable str.center(), str.[r]partition() and builtin compile()

cc3200 port:
- add ssl_version argument to ssl.wrap_socket()

esp8266 port:
- Makefile: rename SCRIPTDIR to FROZEN_DIR for consistency with FROZEN_MPY_DIR
- ets_alt_task: ets_post: Should return 0 on success, !0 - failure
- esp_mphal: add tentative change to mp_hal_stdin_rx_chr() to wait IRQ
- extend system microsecond counter to 64-bits; use in ticks_ms
- add uos.statvfs() to get filesystem status
- moduos: move stat/statvfs funcs to sit within #if VFS guard
- modmachine: idle(): Return number of CPU cycles spent idling
- main: put /lib before / in sys.path
- modpybrtc.c: implement machine.RTC.alarm_left()
- make PY_UHASHLIB_SHA1 config depend on PY_USSL and SSL_AXTLS
- add FLASH_MODE,FLASH_SIZE options for make deploy target
- use mp_raise_OSError helper function
- make neopixel support configurable
- mpconfigport: enable MICROPY_PY_BUILTINS_SLICE_ATTRS
- enable sys.{stdin,stdout,stderr}.buffer for raw serial access
- enable importing of precompiled .mpy files
- enable micropython.alloc_emergency_exception_buf()

zephyr port:
- initial Zephyr RTOS port, MicroPython part
- initial Zephyr RTOS port, Zephyr part
- add zephyr_getchar module to handle console input
- switch to microkernel, required for network to work in background
- automatically derive ARCH
- support extra make targets
- Makefile: automatically derive target-specific CFLAGS
- use recently added "make outputexports" Zephyr target
- add README
- enable stack checking and micropython.mem_info()
- enable frozen modules support
- main: execute main.py frozen module on boot, if available
- zephyr_getchar: add support for Ctrl+C handling
- add Ctrl+C handling
- implement the help() function
- add copyright blurbs

README:
- remove issue-stats badges, the service is no longer available
- mention _thread module availability in select ports

docs:
- library/pyb.SPI: init(): describe "bits" argument
- library/machine: update description of disable/enable IRQ funcs
- uos: add uos.statvfs() documentation
- wipy: correct deep sleep current figure
- wipy: small doc fixes
- reference: add constrained.rst doc

travis:
- abandon mingw32 in favour of mingw-w64
- run feature and coverage test for precompiled mpy files

examples:
- network/http_client*: use \r\n line-endings in request

Support for stream decompression in uzlib, and more ESP8266 features

This release includes some bug fixes, code clean-up, updates to the docs,
more tests, and various feature additions.  The uzlib module now supports
efficient stream decompression in the form of the uzlib.DecompIO class.
Freezing of bytecode now supports floats for the ESP8266 port, as well as
complex numbers for all ports.  The stmhal port has ADC working on L4
microcontrollers, fixed initialisation for DAC, and addition of the
machine.WDT class and machine.reset_cause function.

For the ESP8266 port Pin(16) now works as an input pin and the hardware
SPI peripheral is exposed as machine.SPI(1).  The os.umount function is
implemented and the port supports mounting of externally connected SD
cards.  The machine.WDT class is added, wlan.scan() is fixed to return all
access points, and there is support for DS18S20 devices.

py core:
- runtime: factor out exception raising helpers
- runtime: define mp_check_self(pred) helper macro
- objdict: get rid of asserts (remove/replace with mp_check_self())
- get rid of assert() in method argument checking functions
- objtuple: in tuple_cmp_helper, use mp_check_self instead of raising
- objstr: use mp_raise_{Type,Value}Error instead of mp_raise_msg
- obj.h: for obj reprs A,B,C use void* explicitly for mp_obj_t typedef
- mpconfigport.h: remove typedef of machine_ptr_t, it's no longer needed
- sequence: allow to use bignums as indices in slice objects
- stream.c: use mp_obj_get_type in mp_get_stream_raise
- gc: add MICROPY_GC_CONSERVATIVE_CLEAR option to always zero memory
- compile: don't compile assert statements when optimisations enabled
- modstruct: use more compact mp_raise_ValueError function
- emitglue: use more compact mp_raise_ValueError function
- rename struct mp_code_state to mp_code_state_t
- mkrules.mk: allow to override name of libmicropython.a
- mpprint: fail an assertion with unsupported format specifiers
- makeqstrdata.py: compute the qstr hash from bytes, not characters
- if str/bytes hash is 0 then explicitly compute it
- emitglue.c: provide mp_raw_code_load_file for any unix architecture
- add MICROPY_USE_INTERNAL_PRINTF option, defaults to enabled

extmod:
- modwebrepl: set_password(): raise exception for too long password
- uzlib/: update uzlib to v2.0: new API supporting stream decompression
- moduzlib: refactor to new stream-compatible uzlib 2.0 API
- uzlib/: update uzlib to v2.0.1: fixes for pedantic compiler warnings
- uzlib/: update uzlib to v2.0.2: consistently use stdint types
- modbtree: do CHECK_ERROR after __bt_seq()
- modubinascii: implement binascii.crc32
- modubinascii: make crc32() support configurable
- modframebuf: fix pixel accessor to return a 1-bit result
- add machine_spi with generic SPI C-protocol and helper methods
- modframebuf: fix fill and scroll when height not divisible by 8
- moduzlib: implement zlib stream decompressor class, DecompIO
- moduzlib: use mperrno.h for error constants
- modframebuf: include font from stmhal directory explicitly
- moduzlib: support wbits arg to DecompIO
- framebuf: add the xstep!=0 case to scroll() method

lib:
- utils/stdout_helpers: fix function signature to match py/mphal.h
- berkeley-db-1.xx: update to upstream, fixes MacOSX build
- utils/pyexec: qstr_pool_info() requires size_t* parameters

drivers:
- sdcard: port the SDCard driver to new machine API, with backwards
  compatibility for pyboard

tools:
- mpy-tool.py: support freezing float literals with obj-repr C
- mpy-tool.py: store qstr config values in global config object
- mpy-tool.py: compute the hash value for str/bytes objects
- mpy-tool.py: support freezing of complex numbers

tests:
- rename zlibd_decompress.py -> uzlib_decompress.py
- basics: add more tuple tests to improve coverage testing
- basics: add more list tests to improve coverage testing
- misc/non_compliant: add tests to improve coverage testing
- basics: add test for break from within try within a for-loop
- basics: add a test file for overriding special methods
- basics/special_methods: enable tests for extra special methods
- uzlib_decompress: actually test raw DEFLATE stream
- run-tests: disable thread/thread_lock4.py on Travis
- run-tests: disable thread/stress_heap.py when running on Travis
- cmdline: add test for -O option to check optimisation value
- extmod/vfs_fat_ramdisk: add tests for VFS.umount()
- run-tests: disable thread_gc1.py test on Travis
- unix/extra_coverage: add test for str/bytes with invalid hash
- extmod: add test for uzlib.DecompIO
- extmod: add a test for framebuf module, tested by coverage build
- extmod/uzlib_decompio: add zlib bitstream testcases
- extmod/framebuf1: add tests for scrolling in the x-direction
- run-tests: disable thread/stress_recurse.py test on Travis

unix port:
- mpconfigport.h: don't include stdio.h on MacOS
- when find'ing frozen files don't use extra slash, do follow symlinks

qemu-arm port:
- enable MICROPY_PY_ALL_SPECIAL_METHODS

stmhal port:
- boards: update STM32L476 pin defs to include ADC channels
- adc.c: get ADC working on STM32L4 MCUs
- fix timer capture/compare interrupt handling for TIM1 and TIM8
- remove obsolete code for special handling of TIM3 irq settings
- make ADC channel 16 available on L4 MCUs
- update pin print to print new constants
- modusocket: set self->nic to MP_OBJ_NULL after socket close
- update boot.py files to use VCP instead of CDC
- spi: factor out SPI transfer code to a single function
- spi: support new machine SPI methods in legacy SPI object
- add machine.WDT class
- set STM32F7DISC CPU Frequency to 216 MHz
- dac: fix DAC (re-)initialisation by resetting DMA
- wdt: implement keyword args to WDT constructor
- modmachine: implement machine.reset_cause() function, and consts
- machine.POWER_ON is renamed to machine.PWRON_RESET
- when find'ing frozen files don't use extra slash, do follow symlinks

cc3200 port:
- add machine.PWRON_RESET constant (machine.POWER_ON is now deprecated)

teensy port:
- fix execution of frozen boot.py and main.py

esp8266 port:
- fix reading of pin object for GPIO16; Pin(16) now works as an input
- PULL_UP is not supported on Pin(16), so raise an exception in this case
- enable support for all special methods
- modpybhspi: add a HSPI module for hardware SPI support
- modmachinespi: add a factory method for SoftSPI/HSPI
- esp_mphal: no longer disable watchdog on startup
- modpybrtc: use 64-bit arithmetic when computing alarm expiry
- hspi: enable duplex operation of hardware SPI
- modous: add os.umount method to unmount a filesystem
- modmachinewdt: implement machine.WDT class
- modules: split onewire.py into OneWire and DS18X20 driver
- modules/onewire: change onewire.read() to onewire.readinto()
- modules/ds18x20.py: add support for DS18S20 devices
- modpybspi: use generic SPI helper methods to implement SPI
- modpybhspi: simplify HSPI driver by using 1 function for xfers
- modmachinewdt: add .deinit() method
- modmachine: add WDT_RESET and SOFT_RESET constants
- modmachine: don't expose internal SoftSPI and HSPI classes
- modmachine: simplify SPI class implementation multiplexing
- espneopixel: disable IRQs during eps.neopixel_write
- modnetwork: fix wlan.scan() method so it returns all networks
- modmachine: map PWR_ON_RESET to vendor's REASON_DEFAULT_RST
- machine.PWR_ON_RESET is renamed to machine.PWRON_RESET
- when find'ing frozen files don't use extra slash, do follow symlinks

docs:
- esp8266/tutorial/pins: fix typo in commands for pin input mode
- esp8266/intro: add command to install esptool.py 1.0.1 via pip
- library/machine.WDT: add note that WDT is only available on WiPy
- esp8266/quickref: fix and update the SPI docs
- esp8266: update quickref and tutorial for OneWire/DS18X20 driver
- pyboard: update USB mouse tutorial to use VCP instead of CDC
- pyboard: update USB mouse tutorial to use pyb.USB_HID()
- library: add reference for pyb.usb_mode and pyb.USB_HID
- pyboard/quickref: add links to pinouts for other pyboard variants
- pyboard/quickref: add section on "delay and timing" for utime mod
- esp8266/quickref: add internal links to docs for some modules
- esp8266/quickref: update information on SPI classes
- esp8266/quickref: further improvements for SPI subsections
- library/machine.WDT: add that WDT is available on pyboard
- reference/isr_rules.rst: two minor additions to docs for using ISR

misc:
- add *.pyc to .gitignore, because Python 2 doesn't use __pycache__
- build mpy-cross as part of the Travis process

Many small improvements and additions, with btree support in ESP8266 port

This release brings various improvements and additions to the core,
extended modules and the ESP8266 port, as well as enhancements to the docs.
There is now a "threshold" function in the gc module for the user to
configure the garbage collector to run earlier than usual, in order to help
reduce fragmentation of the heap.  The btree module is now available in the
ESP8266 port, and there is improved WebREPL file transfer: get file is now
non-blocking (this change requires an update of the client software).

py core:
- nlrx64.S: prefix mp_thread_get_state with an underscore on Mac
- stream: implement 2- and 3-arg write() method as an extension to CPython
- gc: implement GC running by allocation threshold, user configurable
- fix nlrthumb.c when DEBUG=1 is defined
- obj: issue a warning when str and bytes objects are compared
- mpconfig.h: fix description for MICROPY_PY_STR_BYTES_CMP_WARN
- objstrunicode: str_index_to_ptr: should handle bytes too
- objstrunicode: str_index_to_ptr: implement positive indexing properly
- stream: implement generic flush() method, in terms of C-level ioctl
- objstringio: add MP_STREAM_FLUSH ioctl and flush() method
- objstringio: implement MP_STREAM_SEEK ioctl and add seek() method
- stream: add adapter methods with POSIX-compatible signatures
- mpconfig.h: add MICROPY_STREAMS_POSIX_API setting
- py.mk: extra switches to build "embedded" BerkeleyDB BTree lib
- mkrules.mk: allow to add more items for "clean" target using CLEAN_EXTRA
- objstr: make .partition()/.rpartition() methods configurable
- mpconfig.h: define MP_ALWAYSINLINE for reuse

extmod:
- modussl: rename to modussl_axtls.c, to allow impl using other SSL libs
- modussl_axtls: further changes to allow alternative SSL modules
- modussl_axtls: add dummy setblocking() method
- vfs_fat: implement rmdir() method (aliases to unlink)
- modussl_axtls: use mp_stream_close() method
- modwebrepl: use mp_stream_close() method
- modbtree: check __bt_open() return value for error
- modbtree: switch to accepting stream object instead of filename
- modbtree: implement __contains__ operation
- modwebrepl: factor out "GET" iteration to write_file_chunk()
- modwebrepl: make GET_FILE operation non-blocking
- modbtree: open(): add option kwargs
- modwebsocket: add readline method
- modwebsocket: make compatible with non-default object models
- modwebsocket: use mp_rom_map_elem_t and friends
- modwebrepl: add GET_VER operation to query MicroPython version

lib:
- axtls: upgrade to axTLS 1.5.4 + MicroPython patchset
- axtls: update, fixes esp8266 build
- utils/stdout_helpers: move from minimal/uart_extra.c for reuse
- embed/abort_: implementation of abort_() function raising uPy exception
- berkeley-db-1.xx: switch to "embedded" branch
- berkeley-db-1.xx: update, sets default page size to 4096

tests:
- add test for extended arguments to stream .write() method
- extmod/machine_pinbase: skip if machine.PinBase is not available
- bytes_compare: rework test for bytes <-> str comparison
- extmod/btree1: close database at the end of test
- unicode_subscr.py: detailed test for subscripting unicode strings
- run-tests: make "regex'ed .exp" facility available to device tests
- io/bytesio_ext: test for .seek()/.flush() on BytesIO
- extmod/btree1: tests against in-memory DB (using io.BytesIO)
- machine_mem.py: too non-portable, rework as an example for unix port
- machine1: revamp to work with unix port (which has "umachine")
- basics: bytes/str.partition/rpartition are now optional

mpy-cross:
- fix Makefile to handle gc-sections linker flags on OS X
- use binary file translation mode for creating mpy files on windows
- fix mingw and msys2 compilation

minimal port:
- disable MICROPY_GC_ALLOC_THRESHOLD

unix port:
- mpthreadport: adjust minimum thread stack, and stack limit check
- cache libaxtls.a in local build dir
- disable MICROPY_GC_ALLOC_THRESHOLD for minimal build
- enable MICROPY_PY_STR_BYTES_CMP_WARN
- mpconfigport.h: include stdio.h by default
- file: implement MP_STREAM_FLUSH ioctl
- file: ioctl(): check that file is open before operations
- file: fdfile_ioctl(): fix argument to check_fd_is_open()
- file: use generic stream flush() method
- enable websocket module
- moduselect: allow poll.register(), etc. accept fd-like objects

stmhal port:
- fix malloc when used with external libraries
- make SPI NSS pin definition optional
- fix I2C mappings for STM32F429DISC board

esp8266 port:
- select axTLS for SSL implementation, following recent refactor
- moduos: add rmdir() function
- cache Xtensa-built libaxtls.a in local build dir
- enable MICROPY_PY_STR_BYTES_CMP_WARN
- dupterm_task_init() should be called before running _boot.py, etc
- _boot.py: set GC alloc threshold to half of heap size
- _boot.py: decrease GC alloc threshold to quarter of heap size
- modpybuart: fix UART parity setting
- axtls_helpers: remove abort_(), now in lib/embed/
- mpconfigport.h: include sys/types.h for POSIX types definitions
- esp_mphal: implement libc's errno
- enable btree module
- eagle.rom.addr.v6.ld: add Enable_QMode symbol from SDK 2.0.0
- make APA102 driver inclusion configurable
- makeimg.py: store firmware size as last 4 bytes of padding area
- makeimg.py: append md5 hash to the generated binary
- modesp: add check_fw() function to check integrity of the firmware
- scripts/port_diag.py: include esp.check_fw() call
- flashbdev: reserve extra sysparam sector for SDK 2.0.0 compatibility
- scripts/inisetup: add commented-out call to esp.osdebug(None)
- modmachine: implement idle() function
- esp_mphal.h: add mp_hal_ticks_cpu() for reuse
- modutime: actually implement ticks_cpu()
- modmachine: implement dummy sleep() function
- tutorial/intro: reword para abou -fm dio switch
- modules/flashbdev: start filesystem at 0x90000
- esp8266.ld: increase firmware image size to 0x90000 (576K)

docs:
- add DHT to ESP8266 Quick Ref and Tutorial
- fix some spelling mistakes
- array: document array module
- library/index: include array module in ToC
- esp8266/intro: rename to "Getting started" from "Introduction"
- esp8266/intro: add troubleshooting section
- esp8266/quickref: link to installation instructions
- esp8266/tutorial/intro: add anchor for link from quickeref
- esp8266/intro: focus on hazards of unearthed power wrt electronics
- uio: mention seek()/flush() support for io.BytesIO

misc:
- logo/1bit-logo A black & white version of the logo

examples:
- http_server*: update for buffered-like streams (read line by line)
- embedding: example for embedding MicroPython in an app
- embedding: add README
- http_client*: be sure to close socket
- network: split recv- and read-based HTTP servers

qemu-arm:
- enable gcc LTO option for nlrthumb.c

Thread support, ESP8266 memory improvements, btree module, improved docs

This release brings multi-threading support in the form of the _thread
module, which closely matches the semantics of the corresponding CPython
module.  There is support for GIL and non-GIL builds; without the GIL
enabled one must protect concurrent access to mutable Python state at the
Python level using Lock objects.  Threading with the GIL is enabled in
the cc3200 port on the WiPy.  Threading without the GIL is enabled on the
unix port.  The ESP8266 port has support for frozen bytecode (for scripts
in the modules/ subdirectory), as well as optimisations for reduced
memory usage and decreased memory fragmentation.  The ESP8266 RTC also
resumes correctly after a deepsleep.  An initial "btree" module has been
implemented for database support (unix port only), and the documentation
has been further improved, with pre-built PDF versions of the docs now
available.

py core:
- parse: treat constants that start with underscore as private
- objdict: implemented OrderedDict equality check
- support to build berkeley db 1.85 and "btree" module
- mpconfig.h: MP_NOINLINE is universally useful, move from unix port
- makeqstrdefs.py: remove restriction that source path can't be absolute
- mkrules.mk: define "lib" outside conditional block
- rename __QSTR_EXTRACT flag to NO_QSTR
- objtype: instance: inherit protocol vtable from a base class
- mphal.h: if virtpin API is used, automagically include its header
- objtype: inherit protocol vtable from base class only if it exists
- add MP_STATE_THREAD to hold state specific to a given thread
- add basic _thread module, with ability to start a new thread
- modthread: properly cast concrete exception pointer to an object
- modthread: add stack_size() function
- modthread: add exit() function
- modthread: implement lock object, for creating a mutex
- modthread: add with-context capabilities to lock object
- gc: make memory manager and garbage collector thread safe
- modthread: satisfy unused-args warning
- gc: fix 2 cases of concurrent access to ATB and FTB
- modthread: be more careful with root pointers when creating a thread
- modthread: call mp_thread_start/mp_thread_finish around threads
- gc: fix GC+thread bug where ptr gets lost because it's not computed
- make interning of qstrs thread safe
- implement a simple global interpreter lock (GIL)
- don't use gc or qstr mutex when the GIL is enabled, there is no need
- modthread: make Lock objects work when GIL is enabled
- mpthread.h: move GIL macros outside MICROPY_PY_THREAD block
- modthread: allow to properly set the stack limit of a thread
- nlrthumb: convert NLR thumb funcs from asm to C with inline-asm
- nlrsetjmp: update to take into account new location of nlr_top
- mpthread: include mpstate.h when defining GIL macros
- gc: be sure to count last allocated block at heap end in stats
- gc: calculate (and report) maximum contiguous free block size
- builtinimport: disable "imported as namespace package" warning
- mpconfig.h: mention MICROPY_PY_BTREE config option
- objarray: split out header to allow direct access to object
- rename mp_obj_type_t::stream_p to "protocol"

extmod:
- modbtree: initial implementation of "btree" module based on BerkeleyDB
- modbtree: handle default value and error check
- modbtree: implement .items() iterator
- modbtree: actually implement end key support for .items()
- modbtree: items(): Implement "end key inclusive" flag
- modbtree: items(): Implement DESC flag
- modbtree: __getitem__() should raise KeyError for non-existing key
- modbtree: open(): Support "in-memory" database with filename=None
- machine_pinbase: implementation of PinBase class
- machine_pinbase: fix nanbox build
- modlwip: store a chain of incoming pbufs, instead of only one
- modbtree: implement keys(), values(), items() iterators
- modbtree: cleverly implement "for key in btree:" syntax
- modwebsocket: add readinto() method
- modwebrepl: add readinto() method
- modbtree: fix unused argument warning
- modbtree: fixes for nanbox build
- moduos_dupterm: reserve buffer bytearray object for dupterm
- moduos_dupterm: reuse dupterm_arr_obj for write operations

lib:
- berkeley-db-1.xx: add Berkeley DB 1.85 as a submodule
- berkeley-db-1.xx: update to upstream which builds for uPy
- fatfs/option/ccsbcs: follow uPy optional features model
- libm: format code to pass gcc v6.1.1 warning
- libm: remove unused definition of "one"

drivers:
- display/ssd1306: add width arg and support 64px wide displays

tests:
- recursive_iternext: clang/Linux is even more stack-frugal than MacOS
- bench: add testcase to compare bytes(N) vs b"\0" * N
- add testcase for OrderedDict equality
- add a testcase for machine.PinBase class
- extmod: add "btree" module test
- btree1: add testcase for iterating btree object directly
- add tests for _thread module
- add 3 more tests for _thread module
- thread: remove need to sleep to wait for completion in some tests
- thread: add tests for running GC within a thread, and heap stress
- thread: rename thread_stress_XXX.py to stress_XXX.py
- thread: add tests that mutate shared objects
- thread: add test for concurrent interning of strings
- thread: add test for concurrent mutating of user instance
- thread: make stack-size test run correctly and reliable on uPy
- thread: make sure that thread tests don't rely on floating point
- thread: allow thread_sleep1 to run without floating point
- thread: allow some tests to run on ports with not much heap
- meminfo: update for addition of "max free sz" output
- run-tests: If running thread tests on unix, don't run mutate ones

unix port:
- unbreak "minimal" target by disabling FatFs
- mpconfigport_minimal.h: clearly mark where user-define config ends
- deprecate support for GNU Readline (MICROPY_USE_READLINE=2)
- time to build with --gc-sections
- move "utime" module config to C level instead of make level
- Makefile: libffi: Build with -Os
- alloc: add option to use uPy's alloc-exec implementation even for libffi
- alloc: make coverage build and its overzealous warnings happy
- disable FatFs VFS for normal build, keep enabled for coverage
- modmachine: include PinBase class
- modmachine: enable time_pulse_us() function
- fix Makefile to handle gc-sections linker flags on Mac OS
- add basic thread support using pthreads
- file: if write syscall returns because of EINTR then try again
- implement garbage collection with threading
- mpthreadport: use SA_SIGINFO for GC signal handler
- gccollect: provide declaration of exported function
- mpthreadport: suppress compiler warning about unused arguments
- modtime: release the GIL when sleeping
- enable btree module
- Makefile: make "minimal" build be minimal again
- mpconfigport_minimal.h: allow to print a string within 1KB of heap
- main: error out on unknown value of suffix in -X heapsize= option
- main: improve help for -X options a bit
- main: when preparing sys.path, allocate exact strings on uPy heap
- disable the GIL to improve performance of non-thread code

windows port:
- follow unix port changes regarding "utime" module
- msvc: include machine_pinbase.c in build and enable umachine module

stmhal port:
- add board definition files for Olimex STM32-E407
- port of f4 hal commit 1d7fb82 to l4 hal (SD card modifications)
- correct DMA to allow SD card on L4 MCUs
- enable SD card on L4 MCUs

cc3200 port:
- update FreeRTOS to v9.0.0
- define our own FreeRTOS heap so it can go in a special segment
- add basic threading capabilities
- fix call to new exception to be _msg instead of _arg1
- use xTaskCreateStatic instead of osi_TaskCreate
- mpthreadport: make mutex statically allocated
- mpthreadport: properly initialise the main thread's data
- gccollect: use MP_STATE_THREAD(stack_top) to get top of stack
- mpthreadport: scan more root pointers from thread data
- mpthreadport: move mem alloc outside the thread_mutex lock
- enable the GIL
- in FreeRTOSConfig.h, comment on configSUPPORT_STATIC_ALLOCATION
- remove .boot section attribute from osi_TaskCreate function
- start the simplelink spawn task using the static task creator
- shrink the FreeRTOS heap and place TCB+stack in freed location
- allow to compile bootloader with threading enabled
- remove obsolete singleton heart-beat object

teensy port:
- update the README with OSX specific information and tips

esp8266 port:
- modnetwork: use struct bss_info::ssid_len for ESSID length
- let RTC work correctly after deepsleep
- switch floating-point arith routines to BootROM
- Makefile: enable --verify option for esptool.py write_flash
- use RTC to set date & time stamps for files
- main.c: clear the command line history when (re)booting
- enable frozen bytecode, with scripts in modules/ subdir
- README: describe how to build mpy-cross
- websocket_helper.py: avoid extra string allocations
- websocket_helper.py: fix typo in debug output
- modpybuart: allow setting baudrate and other params
- explicitly collect garbage in bootstrap scripts
- switch webrepl_setup to use frozen bytecode
- switch webrepl to use frozen bytecode
- README: promote from "highly experimental" to "experimental"
- main: init recently added dupterm_arr_obj port state var
- esp_mphal: call_dupterm_read: Use readinto() method
- esp_mphal: properly handle dupterm EOF after switching to readinto()

qemu-arm port:
- disable gcc LTO option for nlrthumb.c

docs:
- esp8266/tutorial/network_basics: minor typo fix, ap becomes ap_if
- add link to PDF version of docs in sidebar
- library/network: wipy: fix literal block indentation
- esp.socket: remove unused file
- ure: typo fix
- usocket: there must be empty line after .only::
- library/machine.Pin: mention GPIO and cross-link .value() function
- machine.*: add "currentmodule:: machine" directive
- pyb.*: add "currentmodule:: pyb" directive
- machine.Pin: remove explicit target
- machine.UART: cleanup pyboard section
- machine.*: use proper class case in method headers
- machine.Pin: add class designator to all constants
- pyb.CAN: mark CAN.initfilterbanks() as classmethod explicitly
- pyb.Pin: af_list() is a normal method, not a class method
- pyb.ExtInt,pyb.Pin: mark up class methods as such
- pyb.*: use proper class case in method headers
- pyb.Pin: sort .af() and .af_list() methods together
- builtins: enumerate all builtin functions implemented
- library/index: add builtins.rst
- machine.Pin: disambiguate object call method
- machine*: remove explicit targets and "machine." prefixes on classes
- uctypes: improve documentation
- sys: detailed description of print_exception() diff from traceback module
- add sphinx_selective_exclude extension suite
- conf.py: active sphinx_selective_exclude extensions
- rebuild docs from scratch, as required for proper only:: handling
- select: add an article
- sys: print_exception: Fixes/clarifications
- conf.py: exclude cmath from modindex for wipy
- library: fix typo in docs for usocket.listen()

examples:
- unix/ffi_example.py: update for current "ffi" module API
- unix/ffi_example.py: remove TODO, make output more clear

Many ESP8266 improvements, enhanced WebREPL, and support for STM32L4 MCUs

This release brings general improvements and bug fixes, and some new
features.  There is now a uerror module for consistent errno handling
across ports, as well as textual names of OS errors that are printed when
an OSError is raised.  There is support for frozen packages, via both
frozen scripts and frozen bytecode.  WebREPL on the ESP8266 is greatly
improved with many bug fixes and now supports an unlimited (or very large)
number of reconnects.  The os module on the ESP8266 now has rename, chdir,
getcwd and stat.  The unix port now includes the ussl module by default.
The stmhal port has support for STM32L4 MCUs including the STM32L476
Discovery board and the LimiFrog board.

README:
- add explicit note that subdirs contain more READMEs
- add "make deplibs" to quick build section
- "quick build": Use "make axtls" after all

CODECONVENTIONS.md:
- describe git commit messages conventions

py core:
- obj: add warning note about get_array return value and GC blocks
- objstr: binary type of str/bytes for buffer protocol is 'B'
- runtime: properly handle passing user mappings to ** keyword args
- repl: if there're no better alternatives, try to complete "import"
- mpz: fix bug with overflowing C-shift in division routine
- mpz: do Python style division/modulo within bignum divmod routine
- mpz: fix mpn_div so that it doesn't modify memory of denominator
- vstr: vstr_null_terminated_str(): Extend string by at most one byte
- vstr: change allocation policy, +16 to requested size, instead of *2
- add mperrno.h file with uPy defined errno constants
- add uerrno module, with errno constants and dict
- parse: add uerrno to list of modules to look for constants in
- mperrno: add EAFNOSUPPORT definition
- repl: fix handling of backslash in quotes when checking continuation
- gc: gc_dump_alloc_table(): Show byte/str and (byte)array objects
- gc: make (byte)array type dumping conditional on these types being enabled
- gc: use '=' char for tail blocks when dumping heap
- mperrno: add some more MP_Exxx constants, related to networking
- moduerrno: add more constants to the errno module
- add mp_errno_to_str() and use it to provide nicer OSError msgs
- objfloat, py/modmath: ensure M_PI and M_E defined
- emitglue: fix build on AArch64 (ARMv8, etc.) related to loading .mpy files
- objexcept: don't convert errno to str in constructor, do it in print
- moduerrno: add EACCES, pretty common error on Unix
- gc: gc_dump_alloc_table(): dump heap offset instead of actual address
- objstr: make dedicated splitlines function, supporting diff newlines
- objstringio: add TODO comment about avoiding copying on .getvalue()
- modstruct: raise ValueError on unsupported format char
- stream: support both "exact size" and "one underlying call" operations
- declare constant data as properly constant
- stream: add mp_stream_close() helper function
- mphal.h: provide default prototypes for mp_hal_delay_us/mp_hal_ticks_us
- rework frozen modules support to support packages
- objstr: implement str.center()
- allow to stat and import frozen mpy files using new frozen "VFS"
- makeqstrdata.py: allow to have double-quote characters in qstrs
- objnamedtuple: allow passing field names as a tuple
- moduerrno: add EEXIST, EISDIR, ECONNREFUSED
- modstruct: allow to have "0s" in struct format

extmod:
- modlwip: convert errno's to use MP_Exxx symbols
- modlwip: rework how Python accept callback is called
- when including extmod headers, prefix path with extmod/
- modwebsocket: add close() method
- modwebrepl: add close() method
- moduos_dupterm: dumpterm subsystem is responsible for closing stream
- modussl: make more compatible with non-default obj representations
- machine_i2c: redo mp_hal_pin macros to use open_drain and od_low
- virtpin: initial implementation of open-ended C-level Pin interface
- vfs_fat: replace text error messages by POSIX error numbers
- vfs_fat: add chdir() method
- vfs_fat: add getcwd() method
- vfs_fat: add vfs.stat() method
- add machine time_pulse_us function (at C and Python level)
- machine: add MICROPY_PY_MACHINE_PULSE config for time_pulse_us

lib:
- timeutils/timeutils: timeutils_mktime may accept negative time values

drivers:
- cc3000: rename timeval to cc3000_timeval, to avoid clash
- add C-level function to read DHT11 and DHT22 devices
- display/ssd1306: update SSD1306_SPI to work with new API

tools:
- make-frozen.py: properly escape hex chars when making C strings
- make-frozen.py: quick fix to support package-modules
- mpy-tool.py: add checks for critical configuration vars
- make-frozen.py: update for latest changes in frozen modules support
- mpy-tool.py: include .py extension in frozen filename
- mpy-tool.py: don't strip directories from the frozen source name
- upgrade upip to 0.7: SSL cert warning, use uerrno, better usage message

tests:
- run-tests: factor out list of supported external boards
- disable memoryview tests that overflow int conversion
- basics/string_splitlines: reinstate feature test for splitlines
- struct1: add testcase for an unknown type char
- add testcase for str.center()
- extmod/vfs_fat_ramdisk: add testcases for chdir(), getcwd()
- misc/recursive_iternext.py: increase depth N from 1000 to 2000
- misc/recursive_iternext.py: provide more fine-grained selection of N
- pyb/rtc: make RTC test on pyboard more reliable by calling init()

mpy-cross:
- add -s option to specify the embedded source filename

unix port:
- mphalport: add mp_hal_delay_us() for consistency with other ports
- enable uerrno module
- add ability to include frozen bytecode in the build
- mpconfigport_coverage.h: add dedicated config file for coverage build
- unix_mphal: implement mp_hal_ticks_us()
- support frozen packages
- Makefile: nanbox build is not compatible with modussl, disable
- enable "ussl" module
- mpconfigport.mk: document MICROPY_STANDALONE make-level option
- Makefile: "make axtls": automatically fetch submodules if missing

windows port:
- enable multi-processor compilation for msvc

stmhal port:
- l4: adapt DMA to be able to support STM32L4 MCU series
- l4: adapt startup code, clock configuration and interrupts
- l4: make CCM/DTCM RAM start-up conditional on MCU type
- l4: add support for machine.sleep on STM32L4 MCUs
- dma: make DAC DMA descriptors conditional on having a DAC
- add board files for LIMIFROG board
- for LIMIFROG board, add early-init function to get to DFU mode
- dma: fix builds for boards with an F4 or F7 but no DAC
- sdcard: fix initialisation of DMA TX so that writes work
- can: allow to get existing CAN obj if constructed without args
- fix clock configuration for STM32L476-discovery; also add I2C2
- convert to use internal errno symbols; enable uerrno module
- for network drivers, convert to use MP_Exxx errno symbols
- led: allow LEDs to be in PWM mode with TIM1 and channels 1-4
- i2c: expose I2CHandle3 for use by custom C code
- sdcard: allow to do unaligned read-from/write-to SD card
- support frozen packages using .mpy files
- moduos: getcwd(): use mp_obj_new_exception_arg1()
- dac: add DAC deinit() method
- uart: fix wrong baudrate calculation for stm32l4 series

esp8266 port:
- scripts/: remove use of pin.PULL_NONE
- scripts/inisetup: don't start WebREPL on boot in master branch
- scripts/: add fill() to NeoPixel
- scripts/webrepl: add optional password argument to webrepl.start()
- scripts/webrepl: add start_foreground() method
- main: bump heap size to 28K
- mpconfigport: reduce various parser-related allocation params
- help: add "sta_if.active(True)" command
- convert to use new MP_Exxx errno symbols
- enable uerrno module, weak linked also as errno
- change to use internal errno's
- moduos.c: addition of the rename method to module uos
- scripts/port_diag: add network diagnostic output
- scripts/webrepl_setup: show password placeholder char
- scripts/webrepl_setup: add max password length check
- README: add a very first start section
- add APA102 serial individually controllable LEDs support
- enable collections.OrderedDict
- main: update _boot module loading for recent frozen modules refactors
- scripts/port_diag: dump network interface IP settings
- esp_mphal: fix NLR buffer leak in call_dupterm_read()
- esp_mphal: handle Ctrl+C from dupterm (e.g. WebREPL)
- esp_mphal: mp_uos_dupterm_deactivate() may raise exception
- add mp_hal_pin_input() and mp_hal_pin_output() functions
- modpybspi: configure pins when initialising an SPI object
- xtirq: add xtirq.h for controlling xtensa irqs
- ets_alt_task: don't run ets_loop_iter if irqs are disabled
- modmachine: add disable_irq and enable_irq functions
- enable DHT C-level driver
- add dht.py script for high-level control of DHT11/DHT22 sensor
- Makefile: document "disable" value for UART_OS
- modnetwork: scan() is only supported by STA when it's enabled
- modnetwork: protect scan() callback against memory errors
- modnetwork: allow to press ctrl-C while scan() is running
- uart: properly initialise UART0 RXD pin in uart_config
- moduos: add chdir() and getcwd() functions
- scripts/ntptime: allow to override NTP server
- modmachine: add machine.time_pulse_us function
- enable MICROPY_PY_IO_FILEIO to get compliant text/binary streams
- moduos.c: add stat() to the module uos of esp8266
- rtc: set RTC user memory length to 0 on first boot
- provide a dedicated variable to disable ets_loop_iter
- modpybrtc: handle RTC overflow

docs:
- machine.UART: filter out unimplemented UART methods from esp8266 docs
- esp8266/quickref: new way to get MAC address
- esp8266/quickstart: remove i2c examples with stop=False
- ustruct: describe supported type codes
- ussl: add basic description of axTLS-based modussl
- esp8266: Include ussl module in the docs
- machine: make disable_irq and enable_irq docs available for all
- library/machine: add documentation for machine.time_pulse_us
- math, cmath: add port availability information
- library/index: add intro paragraph regarding availability of modules
- README: add some hints for PDF docs generation
- wipy/tutorial: add note about screen key bindings on OS X
- esp8266/quickref: update WebREPL section for 1.8.1 release
- esp8266: fix ESP8266 Network tutorial
- esp8266/quickref: use local image of Adafruit Huzzah board
- esp8266/general: add note about RTC overflow

travis:
- install gcc-arm-none-eabi with --force-yes for now

First general release of ESP8266 port, and support for frozen bytecode

This release marks the first general release of official ESP8266 support
within the MicroPython code base.  The ESP8266 port has many improvements
and additions, including: websocket and webrepl modules, deep-sleep mode,
reading on UART, enhanced I2C support, enhanced network configuration,
full sequence of start-up scripts (built-in _boot.py, boot.py and
main.py), improved filesystem support with automatic flash-size detection
as well as documentation and a tutorial.

Known issues with ESP8266 port are:
- Basic SSL support is available but it works only with relatively short
  data lengths (a few kilobytes).
- WebREPL over SSL is not supported.
- Only 5 or so WebREPL sessions in succession can be started (including
  file transfer sessions), after that the board requires a hard reset.
- File transfer over WebREPL has issues with large files (above a few
  tens of kilobytes).
- By design, only one concurrent WebREPL connection is supported.
- Soft reset doesn't reset the network stack.

In addition to ESP8266 support, this release brings frozen bytecode
which allows to compile bytecode offline and link it into the firmware,
completely eliminating the need for compilation (and the associated
RAM usage) at runtime.  Basic async/await syntax is now supported, and
qstrs are now auto-generated in the build system.

A detailed list of changes is given below.

README:
- explicitly point to required dependencies section
- promote "docs" and "tests" to "major components"
- mention support "async" keyword from Python 3.5

ACKNOWLEDGEMENTS:
- add list of 842 backers from the ESP8266 campaign

py core:
- modbuiltins: add comment about setting "_" special var
- add async/await/async for/async with syntax
- fix constant folding and inline-asm to work with new async grammar
- emitglue: move typedef of mp_raw_code_t from .c to .h file
- emitglue: make mp_raw_code_t* arguments constant pointers
- makeqstrdata: factor out some code to functions that can be reused
- add ability to have frozen persistent bytecode from .mpy files
- makeqstrdata: add more names for escaped chars and esc non-printable
- simplify "and" action within parser by making ident-rules explicit
- makeqstrdata: fix rendering of qstrs that have non-printable ASCII
- makeqstrdata: add special case to handle \n qstr
- declare help, input, open builtins in core
- map: change hash-table allocation policy to be less aggressive
- makeqstrdefs: add script to automate extraction of qstr from sources
- frozenmod: pass the source name of the frozen module to the lexer
- rework QSTR extraction to work in simple and obvious way
- divide "split" and "cat" phases of qstr extraction for better efficiency
- fix bug passing a string as a keyword arg in a dict
- move call_function_*_protected() functions to py/ for reuse
- makeqstrdefs.py: windows compatibility
- obj.h: when constructing a small-int cast to mp_uint_t for bit-shift
- emitnative: use MP_OBJ_NEW_SMALL_INT instead of manual bit shifting
- vm: "yield from" didn't handle MP_OBJ_STOP_ITERATION optimization
- modio: rename module name to "uio" for consistency with other modules
- modcollections: rename module name have "u" prefix for consistency

extmod:
- add initial framebuf module
- add generic machine.I2C class, with bit-bang I2C
- machine_i2c: fix I2C reading by sending ack/nack at end of byte
- machine_i2c: implement I2C memory reading/writing
- moduos_dupterm: don't swallow exceptions in dupterm's read()/write()
- modlwip: lwip_tcp_receive(): Properly handle EOF for non-blocking sock
- modlwip: more debug messages for various edge conditions
- fsusermount: in mount/mkfs, deregister VFS object on error
- modlwip: lwip_tcp_send(): full error handling
- modlwip: lwip_tcp_receive(): full error handling
- modlwip: add ability to run callback on "recv" and "accept" events
- machine_i2c: allow mp_hal_pin_obj_t to be any type, not a ptr
- modlwip: protect recv/accept Python callback against exceptions
- modlwip: workaround esp8266 sendto issue where 1 is returned
- modlwip: add print_pcbs() debug function
- modwebsocket: handle CLOSE control frame
- modussl: throw Python exceptions in case of errors
- modussl: support server-side SSL sockets
- modussl: SSL_OK from ssl_read() means "no user data so far"
- modwebrepl: module to handle WebREPL protocol
- modwebrepl: initial implementation of "get file" operation
- modwebrepl: keep reading data when there's something to read
- modwebrepl: GET_FILE: Send length-prefix chunk with one write()
- modwebrepl: add rate-limiting workaround for broken network drivers
- modwebrepl: set debugging by default to off
- modwebrepl: add support for password
- modlwip: implement sendall() method for TCP sockets
- fix typo of macro that detects if float is enabled

lib:
- utils/printf: rework overriding printer of DEBUG_printf()
- utils/pyexec: condition-out GC calls from pyexec
- utils/pyhelp: extract implementation of help(obj) to a library function
- axtls: update to the latest upstream, fix reported MacOSX build issue

drivers:
- add SSD1306 OLED driver, with I2C and SPI interfaces

tools:
- mpy-tool.py: new tool to work with .mpy files; currently it can freeze them
- mpy-tool.py: add support for Python 2.7

tests:
- add 6 tests for async await/for/with
- add .exp files for async tests, so they can run with Python 3.4
- fix dict1.py so it doesn't rely on the order of dict elems
- extmod: move split-on-empty-match tests to a separate test file
- add testcase for yielding from a stopped generator
- run-bench-tests: process tests in alphabetical order
- update for _io/_collections module having been renamed

minimal port:
- add example of frozen persistent bytecode (.mpy file)
- disable async/await syntax

unix port:
- build with MICROPY_PY_UHASHLIB_SHA1 if already building with axTLS
- make sure build dir exists before accessing it for freezing upip
- Makefile: make install more compatible (BSD, etc.)

windows port:
- msvc: implement automatic qstr generation using makeqstrdefs

stmhal port:
- implement basic C-level pin HAL
- use new generic I2C object in machine module
- enable framebuf module
- properly handle RTS/CTS flow control for buf/unbuf transfers
- add Makefile option FROZEN_MPY_DIR to support frozen bytecode
- for frozen bytecode generation, add dependency of qstr file
- l4: add CMSIS files to support STM32L476
- l4: add basic STM32L4xx HAL files
- l4: adapt UART HAL to avoid 64-bit integer division
- update HALCOMMITS due to change to hal
- l4: add board definition files for STM32L476DISC
- l4: add line to Makefile for building L4 series
- l4: modify adc.c to add support for STM32L4 series
- l4: modify uart.c to support L4 MCU
- l4: modify usbd_conf.c to support L4 MCU
- l4: modify rtc.c to support L4 MCU
- l4: modify timer.c to support L4 MCU
- fix machine.unique_id() function to work for all MCUs
- l4: modify mphalport to support L4 MCU
- l4: modify flash.c and storage.c to support L4 MCU
- l4: add support for external interrupts/events
- accel: raise an exception if the accel couldn't be initialised
- use pyhelp_print_obj function
- change i2c.scan() method to scan addresses 0x08-0x77
- fix typo of macro that detects if float is enabled

cc3200 port:
- use pyhelp_print_obj function
- change i2c.scan() method to scan addresses 0x08-0x77
- disable async/await syntax

esp8266 port:
- enable websocket module
- modnetwork: .config(): Check interface whose config is requested
- modnetwork: .config(): Add "authmode" param
- modnetwork: .config(): Add "password" param (W/O)
- add Python modules for initial configuration
- scripts/inisetup.py: set WPA/WPA2 AP mode with a predefined password
- protect modpyb.h header file from multiple inclusions
- implement basic C-level pin HAL
- switch from using custom I2C driver to generic extmod one
- enable framebuf module
- in callback helpers, pop nlr_buf on successful call
- esp_mphal: don't swallow exceptions in dupterm's read()/write()
- esp_mphal: call_dupterm_read(): Fix order of deactivating on EOF
- remove pin_id field from C pin object
- add dummy entries for non-existing pins to simplify pin logic
- add hard IRQ callbacks for pin change on GPIO0-15
- separate 1-wire timing funcs from Python module to save iRAM
- switch integer arith routines to BootROM
- scripts/port_diag.py: module to collect diagnostic info
- enable input() builtin
- scripts/_boot: mount block device on "" instead of "/"
- moduos: add uos.mkdir function
- modmachine: add reset_cause() function
- adapt port to use new auto-qstr generation
- moduos: add dupterm_notify() function
- esp_mphal: protect dupterm_task_handler() from recursive exec
- README.md: update feature list for current state of affairs
- modesp: allow esp.deepsleep to take 2nd arg for RF wake opt
- scripts/flashbdev: use all available space in 1MB FlashROM for FS
- modesp: add flash_size() function
- scripts: don't try to create filesystem on 512KB devices or less
- modnetwork: .config(): Add "channel" param
- scripts/flashbdev: disable debug output/checks
- scripts/_boot: print notice when initial setup is executed
- scripts/flashbdev: correct bootloader flash size to match real size
- modnetwork: .config(): Add "hidden ESSID" param
- implement basic deep-sleep capabilities
- add uart_rx_wait and uart_rx_char functions
- implement UART.read functionality
- uart: remove obsolete UART rx buffering code
- esp_mphal: remove mp_hal_feed_watchdog
- convert mp_hal_pin_obj_t from pin ptr to simple integer
- allow GPIO16 to be used as a pin in the uPy pin HAL
- change software SPI driver to use general pin HAL
- scripts/websocket_helper: module encapsulating handshake sequences
- scripts/websocket_helper: disable debug output
- scripts/webrepl: webREPL based on C-level websocket object
- scripts/webrepl: convert to persistent daemon
- scripts/webrepl: don't start on import
- scripts/webrepl: allow to override port
- scripts/webrepl: print connection address
- scripts/webrepl: print client address for incoming connections
- scripts/flashbdev: use all available Flash for filesystem
- scripts/webrepl: add "ws://" to "daemon started at" message
- Makefile: add target to build axTLS
- esp8266.ld: put axTLS to FlashROM
- Makefile: override abort() when building axtls
- axtls_helpers: helper/wrapper functions for axTLS
- tests/onewire.py: don't run test on import
- Makefile: support linking with axTLS built from source
- Makefile: enable "ussl" module; axTLS should be built first using "make axtls"
- move pyb.info() function to esp module and remove pyb module
- move onewire.py, neopixel.py drivers from tests/ to scripts/
- scripts/onewire.py: simplify and improve 1-wire driver
- scripts/neopixel.py: remove test function from neopixel driver
- set suitable values for axtls's RT_MAX_PLAIN_LENGTH & RT_EXTRA
- README: add recently required step of 'make axtls'
- modnetwork: make WLAN.ifconfig() read/write
- help: implement help() builtin
- help: add cheatsheet for basic WiFi configuration
- enable WebREPL file transfer rate limiting
- enable webrepl module
- scripts: move all of initial setup to inisetup module
- scripts/inisetup: create default boot.py in filesystem
- scripts/webrepl: connection ack prompt is now printed by modwebrepl
- scripts/webrepl: switch to using _webrepl object wrapper
- scripts/webrepl: add "first connection" mode to setup password
- README: mention WebREPL
- Makefile: be sure to pass cross-compiling AR when building axtls
- scripts/webrepl_setup: reject too short passwords
- change platform name from ESP8266 to esp8266
- modnetwork: remove deprecated wifi_mode()
- esp_mphal: add ets_esf_free_bufs(), etc. functions
- modesp: add esf_free_bufs() debugging function
- modesp: add malloc() and free() functions
- scripts/inisetup: enable WebREPL auto-start on boot
- modnetwork: remove .mac() method, move to .config("mac")
- scripts/inisetup: update for nic.mac() method being gone
- scripts/neopixel.py: swap red and green in pixel accessor
- modpybpin: use enum+array instead of struct for parsing args
- modpybpin: use None instead of PULL_NONE for no-pull config
- modpybpin: make pin.irq() methods take keyword args
- tutorial: mention that esptool is available via pip
- scripts/ntptime: add simple NTP client

docs:
- esp: enumerate flash access functions
- machine: start to update for esp8266 port
- speed_python: clarify/generalize "Buffers" subsection
- speed_python: generalize "Floating point" subsection
- speed_python: add many more details on memoryviews
- machine: reset_cause() has been implemented for esp8266
- topindex.html: esp8266: Enable quickref/general on the main page
- esp8266/general: start "General information" for esp8266
- esp8266: add info about using deep-sleep mode to quickref
- esp8266/tutorial: add tutorial placeholder page
- ustruct: there's no complete "struct" module, only "ustruct" subset
- esp8266: include usocket module reference
- library/usocket: add link to CPython's socket module
- usocket: socket-specific exceptions are for WiPy only
- usocket: socket.IPPROTO_SEC is WiPy-specific
- usocket: describe address format once at the beginning
- network: esp8266: scan(): add note that bssid is bytes object
- library: group MicroPython-specific modules under separate heading
- library/index: move WiPy "micro-libraries" under corresponding heading
- library/index: esp8266 has the same set of stdlibs as pyboard/unix
- module "time" is actually "utime"
- library/index: make single section for "micro-ified" modules
- library/index: order sections from the most to least standard modules
- Makefile: default BUILDDIR based on MICROPY_PORT
- library: "os" module is actually "uos"
- fix uos and utime heading underlines to be the correct length
- library/utime: add more time functions for unix and esp8266 ports
- utime: describe time() peculiarities in MicroPython
- utime: describe sleep() peculiarities in MicroPython
- library: consistently use admonitions for CPython differences
- ubinascii: clean up grammar
- network: esp8266: Add wlan.ifconfig() method
- network: esp8266: Describe wlan.config() method
- make the short port names in the port/version sidebar lowercase
- esp8266: update quickref to reflect changes to 1-wire and NeoPixel
- library/utime: elaborate on epochs and calendar time maintenance
- esp8266/quickref: add info about WebREPL
- ustruct: document pack_into(), unpack_from()
- sys: document sys.modules
- ustruct: fix argument formatting
- sys: remove port-specific details from description of stdin/out/err
- sys: clarify description of sys.exit()
- sys: clean up print_exception() description
- sys: describe sys.implementation
- sys: describe sys.maxsize
- sys: describe sys.platform is port-neutral manner
- add _collections module reference
- add _io module reference
- _io and _collections were renamed to have standard "u" prefix
- library/machine.I2C: update to reflect ESP8266 implementation
- esp8266/general: webREPL is described in quickref for now
- esp8266/general: add more points to "Multitude of boards" section
- esp8266/general: fix list formatting
- esp8266/general: add techspec section
- esp8266/general: add "Boot process" section
- esp8266_contents: reference general and tutorial docs
- network: esp8266: MAC address is set via .config() method
- esp8266: add ESP8266 tutorial
- machine: generalize docs from just WiPy to other ports
- machine: move WiPy-specific hardware details to its general reference
- machine: more generic description of sleep's, WiPy details to its genref
- machine: idle() description generalization
- library/machine.Pin: update pin docs to reflect ESP8266 support
- esp8266/tutorial: update pins tutorial to reflect changes in API

examples:
- http_server_ssl.py: add HTTPS server example

New MicroPython cross-compiler, and vastly improved ESP8266 port

This release adds the MicroPython cross-compiler that can generate .mpy
files (pre-compiled bytecode) which can be executed within any
MicroPython runtime/VM.  The ESP8266 port is also vastly improved thanks
to a hugely successful Kickstarter campaign.  This port now has an
alternative event loop implementation to allow proper Berkeley sockets
using lwIP built from source, and a greatly improved network module.
Many extension modules are now enabled (ujson, ubinascii, uctypes,
uhashlib, urandom, uheapq, ure, uzlib) and the machine module includes
Timer, Pin, PWM, ADC, I2C, SPI, and basic UART.  Bignums are supported,
along with 30-bit precision floating point, and normal error messages.
There is FatFS support and uos.dupterm.

Many other improvements and bug fixes have been made to the core and
other ports.  The basic test suite can now run within a 16k heap.  Inline
assembler functions now support 4 arguments.  The Unix port has the -i
option to start the REPL after a script is finished.  The stmhal port now
exposes the flash and SD card as proper objects with the block protocol.
There is support for generic STM32F439 boards, the NUCLEO-F411RE board,
and targets to deploy via ST-LINK and OpenOCD.

py core:
- mpprint: fix sign extension when printf'ing %u, %x and %X
- vm: fix popping of exception block in UNWIND_JUMP opcode
- objstr: for str.format, add nested/computed fields support
- objstr: for str.format, don't allocate on the heap for field name
- extend native type-sig to use 4 bits, so uint is separate to ptr
- mpz: complete implementation of mpz_{and,or,xor} for negative args
- mpz: add commented-out mpz_pow3_inpl function, to compute (x**y)%z
- viper: allow casting of Python integers to viper pointers
- viper: allow uint as index to load/store, and give better error msg
- objarray: implement "in" operator for bytearray
- mpstate.h: fs_user_mount is now standard, reusable uPy functionality
- asmx64: add helper macro for generating REX_[WRXB] bits from a reg64
- asmx64: support all 16 regs in reg to memory move instructions
- emitnative: add check that RHS of viper store is of integral type
- repl: check for an identifier char after the keyword
- vm: add macros to hook into various points in the VM
- parse: use m_renew_maybe to ensure that memory is shrunk in-place
- malloc: provide a proper malloc-based implementation of realloc_ext
- emitinlinethumb: use qstrs instead of char* for names of asm ops
- add MICROPY_DYNAMIC_COMPILER option to config compiler at runtime
- stackctrl: add mp_stack_set_top() to explicitly set stack top value
- emitglue: get persistent bytecode working on Linux ARM platform
- objboundmeth: allocate arg state on stack if heap alloc fails
- use MP_SMALL_INT_POSITIVE_MASK to check if uint fits in a small int
- fix passing of some wide int types to printf varg format list
- objarray: fix array slice assignment when array is reallocated
- formatfloat: fix buffer overflow when formatting tiny numbers
- objfun: allow inline-asm functions to be called with 4 arguments
- frozenmod: allow port to override lexer to use for frozen modules
- parse: don't allocate an extra parse node for power exponent
- parse: when looking up consts, check they exist before checking type
- stream: add mp_stream_writeall() helper function
- stream: fix object vs ptr usecase in mp_stream_writeall()
- modio: initial implementation of io.BufferedWriter class
- modio: implement io.BufferedWriter.flush()
- modio: io.BufferedWriter: describe flushing policy
- formatfloat: fix case of float format where leading digit was "10"
- formatfloat: fix further cases of buffer overflow in formatting
- parsenum: use pow function to apply exponent to decimal number
- ringbuf.h: add reusable ring buffer class
- map: prevent map resize failure from destroying map
- move stream-related declarations from obj.h to stream.h
- combine continuous block of emit steps into with_cleanup emit call
- implement basic with support in native emitter
- objarray: fix array.append so it doesn't extend if append fails
- stream: add bigger inventory of stream ioctl's
- stream: add Python-level ioctl() method

extmod:
- update uzlib to 1.2.2
- fsusermount: introduce separate mkfs() function
- fsusermount: implement separate umount() function
- fsusermount: change block protocol to support ioctl method
- modmachine: truncate integers that are to be stored using mem*
- fsusermount: expose umount as a public function
- fsusermount: support mounting of multiple block devices
- vfs_fat: object-oriented encapsulation of FatFs VFS
- vfs_fat_diskio: reusable FatFs module, move from stmhal/diskio
- vfs_fat_file: reusable FatFs module, move from stmhal/file
- vfs_fat_ffconf: reusable FatFs module, move from stmhal/ffconf
- vfs_fat: move listdir() method from stmhal for reuse
- vfs_fat: add .remove() method
- vfs_fat: add .mkdir() method
- vfs_fat: add fat_vfs_import_stat(), reusable import stat routine
- vfs_fat: add .rename() method
- vfs_fat: add lexer, move from stmhal port for reuse
- vfs_fat_lexer: make conditional on FatFs support enabled
- modlwip: add .print() method
- modlwip: implement dummy setsockopt()
- modlwip: add stream protocol read method
- modlwip: add dummy .makefile() method
- modlwip: add stream .read() and .readline() methods
- modlwip: check for state change during recv busy-wait loop
- modlwip: still process remaining incoming data of a closed socket
- modlwip: add .write() stream method
- modlwip: support non-blocking recv()
- modlwip: factor out "socket connected" check to a function
- modlwip: use MICROPY_EVENT_POLL_HOOK for event polling if defined
- modlwip: rework getaddrinfo() data passing
- modlwip: add socket.setblocking() method
- modlwip: lwip_tcp_receive: Properly map lwIP error to POSIX errno
- uctypes: use mp_binary_get_val helper when extracting value
- uctypes: finish support for FLOAT32 and FLOAT64 types
- modwebsocket: start module for WebSocket helper functions
- modwebsocket: implement read support
- modlwip: add SOL_SOCKET and SO_REUSEADDR constants for setsockopt()
- modlwip: implement setsocketopt(SO_REUSEADDR)
- modlwip: lwip_tcp_send: handle properly send buffer full condition
- modlwip: add lwip->POSIX error map for lwIP 1.4.0
- modlwip: lwip_socket_setsockopt: handle option value properly
- vfs_fat_diskio: actually support sectors != 512 with Python blockdevs
- modwebsocket: properly check number of args to constructor
- modure: re_exec() renamed to ure_exec() due to collison in 4.3BSD
- modwebsocket: make sure to propagate EOF
- modwebsocket: reset mask between packets
- modwebsocket: add option for blocking writes to non-blk sockets
- modwebsocket: record current fragment type (binary/text/etc.)
- modwebsocket: allow to get type of last read data using ioctl()
- modwebsocket: implement MP_STREAM_SET_DATA_OPTS ioctl
- modwebsocket: split websocket-related defines for reuse
- modlwip: fix for loss of data in unaccepted incoming sockets
- modwebsocket: support write size beyond 125 bytes

lib:
- fatfs: add support for sector sizes larger than 512 bytes
- axtls: update to the latest upstream master

drivers:
- sdcard: add support for multi-block read/write; add SD test

tests:
- open_plus: add tests for "r+", "w+" open modes
- pyb: add simple test for stm module on pyboard
- run-tests: add esp8266 target
- bytearray1: add testcases for "in" operator
- vfs_fat_ramdisk: add test for VfsFat
- vfs_fat_ramdisk: switch to ioctl-based blockdev API
- vfs_fat_ramdisk: allow to override sector size
- vfs_fat_ramdisk: skip test if can't allocate ramdisk
- skip uctypes and urandom tests not supported byt the WiPy
- vfs_fat_ramdisk: add .listdir() testcase
- vfs_fat_ramdisk: add testcase for .remove()
- vfs_fat_ramdisk: add testcase for .mkdir()
- vfs_fat_ramdisk: allow to run in native mode (don't use "with")
- vfs_fat_ramdisk: add testcase for .rename()
- reduce large object allocations so tests can run with small heap
- print_exception: use exception which prints the same regardless of config
- recursive_iternext.py: make low-heap friendly
- run-tests: simplify handling of newline in output from tests
- run-tests: add cmd line option "--heapsize"
- split large tests into smaller files, to run with a small heap
- add new subdir "stress/" specifically for stress tests
- add a test for argument passing to inline-asm functions
- add test for io.BufferedWriter
- wipy: add Timer class tests
- float2int_fp30: variant of float2int for 30-bit stuffed float
- string_format_fp30: variant of string_format for 30-bit stuffed float

mpy-cross:
- add new component, a cross compiler for MicroPython bytecode
- give a more sensible error message when file doesn't exist
- remove setting of MICROPY_FORCE_32BIT=1 from Makefile

unix port:
- file: stop assuming that O_RDWR == O_RDONLY | O_WRONLY
- enable VfsFat support
- enabled importing of persistent bytecode (.mpy files)
- modsocket: add comment regarding close() error checking (which is none)
- unix_mphal: hack to make uos.dupterm() actually work
- implement -i option (inspect - start REPL after script is finished)
- file: parse "buffering" argument of open() builtin
- file: "encoding" arg to open() isn't kw-only
- djgpp errno.h have no ENOTSUP, so define it to Linux value
- freedos: strip and size names for binaries

stmhal port:
- diskio: introduce MICROPY_HW_HAS_FLASH setting
- move stmhal-specific FatFs routines/structs to fatfs_port.c
- file: recast as "FatFs file" class, to support other VFS types
- file: for self-contained usecase, don't define global types
- improve NUCLEO-F401RE build, with UART2 as REPL
- expose flash and SD card as proper objects with block protocol
- add mount/umount/mkfs to os module
- add a function for setting the pin alternate function
- NUCLEO 401 - Add a bunch of missing pins and reorder the pins
- CERB40 - Add pins defines for I2C3
- NUCLEO 401 - Add definitions for I2C2 and I2C3
- diskio: add provision for default returns for ioctl INIT/SEC_SIZE
- improvements to the STM32F4DISC UART config settings
- enabled importing of persistent bytecode (.mpy files)
- make SPI use mp_hal_gpio_set_af
- switch from dfu-util to tools/pydfu.py for default deploy method
- add stmhal-specific README.md with extra details for this port
- add makefile target to deploy stmhal build via ST-LINK
- add support for generic STM32F439 board (non DISCO)
- add makefile target and configuration to deploy via OpenOCD
- add board definition files for NUCLEO_F411RE
- rename STM32F401NUCLEO to NUCLEO_F401RE
- NUCELO_F401RE cleanup
- consistently enable USB SOF Irqs for all USB modes (FS and HS)

qemu-arm port:
- reinitialise uPy heap and runtime at start of each test
- enable builtin override feature, and enable more tests

cc3200 port:
- add stmhal/builtin_open.c to build
- fix breakage after VfsFat refactor
- finally fix the Timer class API
- improve robustness of the I2C driver
- simplify the Timer API and correct the documents
- fix "debug" build
- improve robustness of WLAN during sleep modes
- rename 'server' class to 'Server' for consistency
- update WiPy software version to 1.2.0

esp8266 port:
- modesp: implement flash_write(), flash_erase()
- README: add hint about adding toolchain to PATH
- modpybrtc: simplify multiplication by fixed-point value
- switch bignum implementation from long-long to mpz
- enable float support, using 30-bit stuffed floats
- enable math module
- allow Makefile's PORT variable to be overridden
- change "soft reboot" message to work with pyboard.py
- add network.ifconfig()
- enable ujson, ubinascii, and uctypes modules
- esp8266.ld: link in SDK version section
- enable config settings helpful for debugging
- enable uhashlib module
- enable more features in mpconfigport.h
- add mp_hal_delay_us function
- add time.{sleep_ms,sleep_us,ticks_ms,ticks_us,ticks_diff}
- reset "virtual RTC" on power on
- modutime: support float argument to time.sleep()
- add modmachine with mem* arrays
- modmachine: basic implementation of Timer for OS virtual timers
- modmachine: changing params of a timer requires disarming it first
- etshal.h: add timer functions prototypes
- modmachine: use etshal.h
- modmachine: timer: Add ONE_SHOT and PERIODIC symbolic constants
- add custom _assert() function
- implement Pin.__call__() and Pin.OPEN_DRAIN mode
- expose simple pin API at C level
- modpybpin: add support for GPIO16
- modmachine: add Pin class from modpyb
- etshal.h: more prototypes of ESP8266 SDK/BootROM functions
- support raising KeyboardInterrupt on Ctrl+C
- uart: add uart_flush() function
- allow Makefile's BAUD variable to be overridden
- enable stack overflow checking
- don't gc-collect BSS
- enable modlwip
- Makefile: add define for ESP8266 lwIP
- put more code in iROM section
- main: module to run on boot is "boot", not "main"
- move pyb.freq to machine.freq
- modnetwork: allow to configure STA and AP interfaces separately
- move wifi_mode() and phy_mode() to network module
- modnetwork: add per-interface .active() method
- modnetwork: move config defines to the top
- modnetwork: introduce interface .config() method
- modnetwork: add symbolic names for network interfaces: STA_IF & AP_IF
- add alternative event loop implementation
- feed WDT in ets_loop_iter()
- ets_alt_task: be sure to "pop" event before calling its handler
- ets_alt_task: update for vendor SDK 1.5.0
- esp_mphal: add higher-level event polling function
- define MICROPY_EVENT_POLL_HOOK for the port
- switch to lwIP built from source
- store frozen modules in FlashROM
- ets_alt_task: make FIRST_PRIO=0 to cover all task priorities
- make mp_hal_delay_us work with new event framework
- enable urandom module
- add module weak link from json to ujson
- enable more extmod's: uheapq, ure, uzlib
- enable non-blocking stream support
- add "socket" and "usocket" aliases for lwip module
- enable auto-indent in REPL
- expose pin object as a public structure for use as C pin API
- add basic I2C driver, with init and writeto methods
- modpybi2c: add missing include
- clean up bit-bang I2C implementation
- implement bit-bang I2C read, and add i2c.readfrom method
- add onewire helper functions as C module
- add tests/onewire.py as a driver and test code for ds18b20 dev
- implement software SPI class
- add PWM support
- esppwm.c: fix IRQ handler prototype
- put lexerstr32.o into FlashROM
- put utils.o to FlashROM
- link ADC class into machine module
- add esp.neopixel_write function to bit-bang WS2812 data
- tests: add neopixel.py test
- put modpybi2c.o to FlashROM
- set up UART handling task soon into init process
- modesp: flash_write(): Writes in multiples of 4 bytes
- modesp: flash_read(): Accept buffer to read to as a second argument
- README: update for the current status of the port
- enable FatFs support
- esp8266.ld: put FatFs to FlashROM
- deploy: Use --flash_size=8m option to esptool.py
- moduos: add listdir() proxy for MP_STATE_PORT(fs_user_mount)[0]
- moduos: factor out VFS method proxy helper
- moduos: add os.remove(), proxying to VFS object
- zero out fs_user_mount state on (soft) reset
- support importing modules from filesystem
- implement os.urandom function
- add basic support for duplicating REPL output
- enable uos.dupterm() method
- esp_mphal: add support for debug UART-only output
- let esp8266 "os" messages go to standard (REPL) UART
- support synchronous wifi scanning
- fix issue when current REPL line was garbage-collected
- switch back to accumulating input data via ring buffer
- implement input part of dupterm handling
- reset term_obj on reboot
- move PHY mode constants from modesp to modnetwork
- disallow recursive calls to REPL
- support dedicated REPL loop (aka pull-style)
- switch to non event-driven REPL to support paste mode
- uart: get ctrl-C working now that event-based REPL is disabled
- use VM_HOOK to call ets_loop_iter within the VM
- README: add link to docs
- move .rodata where it belongs with -mforce-l32 help
- bump iROM size to 512k
- ets_alt_task: comment out debug output
- minimize gap between Inst/DataRAM segments and FlashROM segment
- switch back to flashing combined firmware (single file)
- update flashing instructions in README
- bump heap size to 24k
- move pyb.hard_reset() to machine.reset()
- move pyb.unique_id() to machine.unique_id()
- modnetwork: require_if(): Report the actual interface required
- make destination for vendor OS debug output soft-configurable
- add initial implementation of machine.UART
- README: add short troubleshooting section
- switch from terse error messages to normal ones
- implement multistage bootstrap sequence
- add esp.freemem() and esp.meminfo() functions
- implement mp_builtin_open() using vfs_proxy_call()

examples:
- http_client.py, http_server.py aren't just unix, move to network/
- http_client.py: improve CPython compatibility in stream mode
- http_client.py: introduce main() function
- http_server.py: refactor/simplify for Python 3.5
- http_server.py: introduce main() function
- http_server.py: bind to 0.0.0.0, to be accessible from other hosts
- http_client_ssl.py: HTTPS client example

docs:
- correct WiPy Timer docs
- minor change to improve clarity in machine.Timer docs
- add note on machine.Timer class regarding PWM output pins
- correct machine.Timer code examples related to duty cycle
- add esp8266 quick reference page, with basic info
- esp8266: minor tweaks to quickref, Timer and I2C classes
- add versions.html template and support code for a version sidebar
- allow list of versions to be specified by environment variable
- esp8266: fix indent errors, typos, and add info about REPL UART
- update asm_thumb2_hints_tips re return type of asm funcs
- update details on using ADCAll object for vref/vbat channels
- add Python speed optimisation guide, including minimal viper ref
- esp8266: update quick reference: i2c.readfrom and neopixel example
- update asm tutorial, maximum number of allowed args is now 4
- update pyb.I2C constructor to reflect changes in Pyboard Lite
- mention that pyb.SPI constructor accepts "X" and "Y" arguments
- update pyb.UART.any() to mention that it returns character count
- topindex.html: refer to "pyb" module only for pyboard
- add standard modules list for esp8266
- network: esp8266: Update docs on WLAN constructor
- more standard modules for esp8266
- esp: remove getaddrinfo(), now in socket module as expected
- esp8266/quickref: note that timers supported are virtual ones
- esp8266/quickref: add note about GPIO16
- esp8266: phy_mode() moved to network module
- esp8266: esp.wifi_mode() replaced with network.WLAN.active()
- esp8266: esp.mac() replaced with network.WLAN.mac()
- correct pin interrupt example code for the WiPy
- network: esp8266: status is WLAN object method
- network: esp8266: .scan() is now synchronous and returns result list
- update copyright notice
- esp8266: esp.socket is deprecated, remove from docs
- os: change wording to be a bit more port-neutral
- machine: change wording to be a bit more port-neutral
- ubinascii: document a2b_base64(), b2a_base64()
- esp8266/quickref: add note about physical vs logical pin numbers
- ubinascii: document non-standard "sep" argument to hexlify()
- esp8266: Enable "machine" module docs

Revision 4 tar ball.

This was packaged as GRL_MPLEON_SW123_rev3.tgz.

leon: This is close to the second SW123 release given to ESA.

Main change from first revision is the addition of the leon-ex-pystone
example.

leon: This is close to the first SW123 release given to ESA.

Main changes were rebasing against latest upstream MicroPython.

IPv6 support in unix, bignum constant folding, urandom module, faster VCP

In this release there are many bug fixes and consolidation of previous
features.  Constant folding in the parser can now operate on arbitrary
precision integers, and the inline assembler is no longer restricted to
using small-ints or 30-bits.  The urandom module has been added with the
most useful random functions included.  The uhashlib module now
implements SHA1.  The Unix port supports IPv6.  The stmhal port has much
faster USB VCP for board to PC transfers, and Timer(3) is now freed up
for general purpose use by the user.

py core:
- frozenmod: make frozen module content be 0-terminated
- frozenmod: store frozen module names together, to quickly scan them
- use polymorphic iterator type where possible to reduce code size
- make dir report instance members
- implement __dict__ for instances
- objstr: in str.format, handle case of no format spec for string arg
- parse: optimise away parse node that's just parenthesis around expr
- change mp_obj_int_is_positive to more general mp_obj_int_sign
- parse: improve constant folding to operate on small and big ints
- inlinethumb: allow assembler to use big ints as args to instructions
- inlinethumb: remove 30-bit restriction on movwt instruction
- viper: truncate viper integer args so they can be up to 32-bit
- emitglue: add more feature flags to .mpy persistent bytecode output
- mpz: fix conversion of float to mpz so it works on big endian archs
- objint: fix classification of float so it works for OBJ_REPR_D
- change type of .make_new and .call args: mp_uint_t becomes size_t
- change type signature of builtin funs that take variable or kw args
- change first arg of type.make_new from mp_obj_t to mp_obj_type_t*
- emitglue: use mp_obj_is_float instead of MP_OBJ_IS_TYPE
- use new code pattern for parsing kw args with mp_arg_parse_all
- add ustruct.pack_into and unpack_from
- modmicropython: add stack_use, heap_lock and heap_unlock functions
- inlineasm: add ability to specify return type of asm_thumb funcs
- runtime: mp_stack_ctrl_init() should be called immediately on startup
- formatfloat: add ability to format doubles with exponents > 99
- builtin property: accept keyword arguments

extmod:
- moduos_dupterm: make uos.dupterm() implementation reusable
- moduos_dupterm: make mp_uos_dupterm_tx_strn() function reusable
- moduos_dupterm: handle exceptions in call to dupterm's .write()
- fix uctypes size calculation for bitfields
- modurandom: add "urandom" module
- modurandom: make yasmarang() function static
- modurandom: add some extra random functions
- moduhashlib: add support for SHA1 (based on axTLS)
- moduhashlib: use MICROPY_PY_UHASHLIB_SHA1 config define
- moductypes: implement assignment for scalar array

tests:
- uctypes: test item assignment for scalar arrays
- object_dict.py: add test for obj.__dict__
- allow float tests to run when MATH_SPECIAL_FUNCTIONS is disabled
- fix math_fun_special test so it passes with single prec float
- remove builtin_dict test
- add some tests for urandom module
- update pyboard LED test
- for pyboard, add test for I2C error handling and recovery

minimal port:
- add enough code to run minimal build on STM32F4xx hardware

unix port:
- unix_mphal: handle exceptions in call to dupterm's .read()
- unix_mphal: be sure to wrap dupterm code with MICROPY_PY_OS_DUPTERM
- modtime: strftime(): Support 2nd argument, but as time_t value
- add socket.inet_ntop function
- allow to build coverage build with OBJ_REPR_D
- add option to build 64-bit NaN-boxing interpreter
- modffi: allow to compile modffi in OBJ_REPR_D mode
- modsocket: accept(): Make IPv6-clean
- modsocket: sockaddr(): Handle AF_INET6 addresses

windows port:
- enable urandom module

stmhal port:
- make stm constants big ints when they don't fit in a small int
- remove custom mod_machine_mem_get_{read,write}_addr functions
- add os.statvfs
- add support for building frozen files
- add support for the STM32F401NUCLEO board
- make USB CDC driver use SOF instead of TIM3 for outgoing data
- make TIM3 available for use by the user
- add PWM capability for LED(3) and LED(4) on pyboards
- in HAL I2C driver, move DMA setup to after sending I2C address

docs:
- fix readthedocs build by updating Latex params
- set author as 'Damien P. George and contributors'
- add link from pyboard switch tutorial to ISR rules document
- include extra functions in time documentation for pyboard
- several minor changes: network, pyb, ADCAll and inline asm
- update to say that Timer(3) is free, and detail LED intensity

travis:
- add unix NaN-boxing build to Travis builds
- switch to Ubuntu 14.04 Trusty