Commit 1570eaf0 authored by Damien George's avatar Damien George
Browse files

drivers: Add SD card driver, controlled via SPI bus.

parent 7690b139
"""
Micro Python driver for SD cards using SPI bus.
Requires an SPI bus and a CS pin. Provides readblocks and writeblocks
methods so the device can be mounted as a filesystem.
Example usage:
import pyb, sdcard, os
sd = sdcard.SDCard(pyb.SPI(1), pyb.Pin.board.X5)
pyb.mount(sd, '/sd2')
os.listdir('/')
"""
import pyb
class SDCard:
CMD_TIMEOUT = const(100)
R1_IDLE_STATE = const(1 << 0)
#R1_ERASE_RESET = const(1 << 1)
R1_ILLEGAL_COMMAND = const(1 << 2)
#R1_COM_CRC_ERROR = const(1 << 3)
#R1_ERASE_SEQUENCE_ERROR = const(1 << 4)
#R1_ADDRESS_ERROR = const(1 << 5)
#R1_PARAMETER_ERROR = const(1 << 6)
def __init__(self, spi, cs):
self.spi = spi
self.cs = cs
self.cmdbuf = bytearray(6)
self.dummybuf = bytearray(512)
for i in range(512):
self.dummybuf[i] = 0xff
self.dummybuf_memoryview = memoryview(self.dummybuf)
# initialise the card
self.init_card()
def init_card(self):
# init CS pin
self.cs.high()
self.cs.init(self.cs.OUT_PP)
# init SPI bus; use low data rate for initialisation
self.spi.init(self.spi.MASTER, baudrate=100000, phase=0, polarity=0)
# clock card at least 100 cycles with cs high
for i in range(16):
self.spi.send(0xff)
# CMD0: init card; should return R1_IDLE_STATE (allow 2 attempts)
if self.cmd(0, 0, 0x95) != R1_IDLE_STATE:
if self.cmd(0, 0, 0x95) != R1_IDLE_STATE:
raise OSError("no SD card")
# CMD8: determine card version
r = self.cmd(8, 0x01aa, 0x87, 4)
if r == R1_IDLE_STATE:
self.init_card_v2()
elif r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND):
self.init_card_v1()
else:
raise OSError("couldn't determine SD card version")
# get the number of sectors
# CMD9: response R2 (R1 byte + 16-byte block read)
if self.cmd(9, 0, 0, 0, False) != 0:
raise OSError("no response from SD card")
csd = bytearray(16)
self.readinto(csd)
if csd[0] & 0xc0 != 0x40:
raise OSError("SD card CSD format not supported")
self.sectors = ((csd[8] << 8 | csd[9]) + 1) * 2014
#print('sectors', self.sectors)
# CMD16: set block length to 512 bytes
if self.cmd(16, 512, 0) != 0:
raise OSError("can't set 512 block size")
# set to high data rate now that it's initialised
self.spi.init(self.spi.MASTER, baudrate=1320000, phase=0, polarity=0)
def init_card_v1(self):
for i in range(CMD_TIMEOUT):
self.cmd(55, 0, 0)
if self.cmd(41, 0, 0) == 0:
self.cdv = 512
#print("[SDCard] v1 card")
return
raise OSError("timeout waiting for v1 card")
def init_card_v2(self):
for i in range(CMD_TIMEOUT):
pyb.delay(50)
self.cmd(58, 0, 0, 4)
self.cmd(55, 0, 0)
if self.cmd(41, 0x40000000, 0) == 0:
self.cmd(58, 0, 0, 4)
self.cdv = 1
#print("[SDCard] v2 card")
return
raise OSError("timeout waiting for v2 card")
def cmd(self, cmd, arg, crc, final=0, release=True):
self.cs.low()
# create and send the command
buf = self.cmdbuf
buf[0] = 0x40 | cmd
buf[1] = arg >> 24
buf[2] = arg >> 16
buf[3] = arg >> 8
buf[4] = arg
buf[5] = crc
self.spi.send(buf)
# wait for the repsonse (response[7] == 0)
for i in range(CMD_TIMEOUT):
response = self.spi.send_recv(0xff)[0]
if not (response & 0x80):
# this could be a big-endian integer that we are getting here
for j in range(final):
self.spi.send(0xff)
if release:
self.cs.high()
self.spi.send(0xff)
return response
# timeout
self.cs.high()
self.spi.send(0xff)
return -1
def readinto(self, buf):
self.cs.low()
# read until start byte (0xff)
while self.spi.send_recv(0xff)[0] != 0xfe:
pass
# read data
mv = self.dummybuf_memoryview[:len(buf)]
self.spi.send_recv(mv, recv=buf)
# read checksum
self.spi.send(0xff)
self.spi.send(0xff)
self.cs.high()
self.spi.send(0xff)
def write(self, buf):
self.cs.low()
# send: start of block, data, checksum
self.spi.send(0xfe)
self.spi.send(buf)
self.spi.send(0xff)
self.spi.send(0xff)
# check the response
if (self.spi.send_recv(0xff)[0] & 0x1f) != 0x05:
self.cs.high()
self.spi.send(0xff)
return
# wait for write to finish
while self.spi.send_recv(0xff)[0] == 0:
pass
self.cs.high()
self.spi.send(0xff)
def count(self):
return self.sectors
def readblocks(self, block_num, buf):
# TODO support multiple block reads
assert len(buf) == 512
# CMD17: set read address for single block
if self.cmd(17, block_num * self.cdv, 0) != 0:
return 1
# receive the data
self.readinto(buf)
return 0
def writeblocks(self, block_num, buf):
# TODO support multiple block writes
assert len(buf) == 512
# CMD24: set write address for single block
if self.cmd(24, block_num * self.cdv, 0) != 0:
return 1
# send the data
self.write(buf)
return 0
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