Commit 2bf04444 authored by Dave Hylands's avatar Dave Hylands Committed by Damien George
Browse files

Add support for pyb.micros() by using the systick timer.

I also removed trailing spaces from modpyb.c which affected a couple
of lines technically not part of this patch.

Tested using: https://github.com/dhylands/upy-examples/blob/master/micros_test.py

which eventually fails due to wraparound issues (I could fix the test to compensate
but didn't bother)
parent 8c0add4e
......@@ -99,7 +99,7 @@ STATIC mp_obj_t pyb_info(uint n_args, const mp_obj_t *args) {
// get and print clock speeds
// SYSCLK=168MHz, HCLK=168MHz, PCLK1=42MHz, PCLK2=84MHz
{
printf("S=%lu\nH=%lu\nP1=%lu\nP2=%lu\n",
printf("S=%lu\nH=%lu\nP1=%lu\nP2=%lu\n",
HAL_RCC_GetSysClockFreq(),
HAL_RCC_GetHCLKFreq(),
HAL_RCC_GetPCLK1Freq(),
......@@ -187,11 +187,46 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(pyb_sync_obj, pyb_sync);
/// \function millis()
/// Returns the number of milliseconds since the board was last reset.
///
/// Note that this may return a negative number. This allows you to always
/// do:
/// start = pyb.millis()
/// ...do some operation...
/// elapsed = pyb.millis() - start
///
/// and as long as the time of your operation is less than 24 days, you'll
/// always get the right answer and not have to worry about whether pyb.millis()
/// wraps around.
STATIC mp_obj_t pyb_millis(void) {
return mp_obj_new_int(HAL_GetTick());
// We want to "cast" the 32 bit unsigned into a small-int. So we shift it
// left by 1 to throw away the top bit, and then shift it right by one
// to sign extend.
mp_int_t val = HAL_GetTick() << 1;
return mp_obj_new_int(val >> 1);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_0(pyb_millis_obj, pyb_millis);
/// \function micros()
/// Returns the number of microseconds since the board was last reset.
///
/// Note that this may return a negative number. This allows you to always
/// do:
/// start = pyb.micros()
/// ...do some operation...
/// elapsed = pyb.micros() - start
///
/// and as long as the time of your operation is less than 35 minutes, you'll
/// always get the right answer and not have to worry about whether pyb.micros()
/// wraps around.
STATIC mp_obj_t pyb_micros(void) {
// We want to "cast" the 32 bit unsigned into a small-int. So we shift it
// left by 1 to throw away the top bit, and then shift it right by one
// to sign extend.
mp_int_t val = sys_tick_get_microseconds() << 1;
return mp_obj_new_int(val >> 1);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_0(pyb_micros_obj, pyb_micros);
/// \function delay(ms)
/// Delay for the given number of milliseconds.
STATIC mp_obj_t pyb_delay(mp_obj_t ms_in) {
......@@ -251,7 +286,7 @@ STATIC mp_obj_t pyb_stop(void) {
/* Enter Stop Mode */
PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);
/* Configures system clock after wake-up from STOP: enable HSE, PLL and select
/* Configures system clock after wake-up from STOP: enable HSE, PLL and select
* PLL as system clock source (HSE and PLL are disabled in STOP mode) */
SYSCLKConfig_STOP();
......@@ -343,6 +378,7 @@ STATIC const mp_map_elem_t pyb_module_globals_table[] = {
{ MP_OBJ_NEW_QSTR(MP_QSTR_USB_VCP), (mp_obj_t)&pyb_usb_vcp_type },
{ MP_OBJ_NEW_QSTR(MP_QSTR_millis), (mp_obj_t)&pyb_millis_obj },
{ MP_OBJ_NEW_QSTR(MP_QSTR_micros), (mp_obj_t)&pyb_micros_obj },
{ MP_OBJ_NEW_QSTR(MP_QSTR_delay), (mp_obj_t)&pyb_delay_obj },
{ MP_OBJ_NEW_QSTR(MP_QSTR_udelay), (mp_obj_t)&pyb_udelay_obj },
{ MP_OBJ_NEW_QSTR(MP_QSTR_sync), (mp_obj_t)&pyb_sync_obj },
......
......@@ -67,6 +67,7 @@ Q(/flash/lib)
Q(/sd)
Q(/sd/lib)
Q(millis)
Q(micros)
// for file class
Q(seek)
......
......@@ -174,6 +174,11 @@ void PendSV_Handler(void) {
*/
void SysTick_Handler(void) {
HAL_IncTick();
// Read the systick control regster. This has the side effect of clearing
// the COUNTFLAG bit, which makes the logic in sys_tick_get_microseconds
// work properly.
SysTick->CTRL;
}
/******************************************************************************/
......
......@@ -27,6 +27,10 @@
#include <stm32f4xx_hal.h>
#include "mpconfig.h"
#include "misc.h"
#include "nlr.h"
#include "qstr.h"
#include "obj.h"
#include "irq.h"
#include "systick.h"
bool sys_tick_has_passed(uint32_t start_tick, uint32_t delay_ms) {
......@@ -41,3 +45,35 @@ void sys_tick_wait_at_least(uint32_t start_tick, uint32_t delay_ms) {
__WFI(); // enter sleep mode, waiting for interrupt
}
}
// The SysTick timer counts down at 168 MHz, so we can use that knowledge
// to grab a microsecond counter.
//
// We assume that HAL_GetTickis returns milliseconds.
uint32_t sys_tick_get_microseconds(void) {
mp_int_t enabled = disable_irq();
uint32_t counter = SysTick->VAL;
uint32_t milliseconds = HAL_GetTick();
uint32_t status = SysTick->CTRL;
enable_irq(enabled);
// It's still possible for the countflag bit to get set if the counter was
// reloaded between reading VAL and reading CTRL. With interrupts disabled
// it definitely takes less than 50 HCLK cycles between reading VAL and
// reading CTRL, so the test (counter > 50) is to cover the case where VAL
// is +ve and very close to zero, and the COUNTFLAG bit is also set.
if ((status & SysTick_CTRL_COUNTFLAG_Msk) && counter > 50) {
// This means that the HW reloaded VAL between the time we read VAL and the
// time we read CTRL, which implies that there is an interrupt pending
// to increment the tick counter.
milliseconds++;
}
uint32_t load = SysTick->LOAD;
counter = load - counter; // Convert from decrementing to incrementing
// ((load + 1) / 1000) is the number of counts per microsecond.
//
// counter / ((load + 1) / 1000) scales from the systick clock to microseconds
// and is the same thing as (counter * 1000) / (load + 1)
return milliseconds * 1000 + (counter * 1000) / (load + 1);
}
......@@ -26,3 +26,4 @@
void sys_tick_wait_at_least(uint32_t stc, uint32_t delay_ms);
bool sys_tick_has_passed(uint32_t stc, uint32_t delay_ms);
uint32_t sys_tick_get_microseconds(void);
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment