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Revise us delay to include interrupt/non-interrupt versions

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This commit is contained in:
Hierophect 2019-11-11 14:58:45 -05:00
parent 1a7060af25
commit 3f8b4727f5
1 changed files with 30 additions and 6 deletions
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36
ports/stm32f4/common-hal/microcontroller/__init__.c
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@ -39,15 +39,39 @@
#include "supervisor/filesystem.h"
#include "supervisor/shared/safe_mode.h"
// This routine should work even when interrupts are disabled. Used by OneWire
// for precise timing.
#include "stm32f4xx_hal.h"
//tested divisor value for busy loop in us delay
#define LOOP_TICKS 12
STATIC uint32_t get_us(void) {
uint32_t ticks_per_us = HAL_RCC_GetSysClockFreq()/1000000;
uint32_t micros, sys_cycles;
do {
micros = ticks_ms;
sys_cycles = SysTick->VAL; //counts backwards
} while (micros != ticks_ms); //try again if ticks_ms rolled over
return (micros * 1000) + (ticks_per_us * 1000 - sys_cycles) / ticks_per_us;
}
void common_hal_mcu_delay_us(uint32_t delay) {
// sys freq is always a multiple of 2MHz, so division here won't lose precision
const uint32_t ucount = HAL_RCC_GetSysClockFreq() / 2000000 * delay / 2;
for (uint32_t count = 0; ++count <= ucount;) {
if (__get_PRIMASK() == 0x00000000) {
//by default use ticks_ms
uint32_t start = get_us();
while (get_us()-start < delay) {
__asm__ __volatile__("nop");
}
} else {
//when SysTick is disabled, approximate with busy loop
const uint32_t ucount = HAL_RCC_GetSysClockFreq() / 1000000 * delay / LOOP_TICKS;
(void)start;
for (uint32_t count = 0; ++count <= ucount;) {
}
}
}
volatile uint32_t nesting_count = 0;
void common_hal_mcu_disable_interrupts(void) {
__disable_irq();
__DMB();
@ -58,7 +82,7 @@ void common_hal_mcu_enable_interrupts(void) {
if (nesting_count == 0) {
// This is very very bad because it means there was mismatched disable/enables so we
// "HardFault".
HardFault_Handler();
asm("bkpt");
}
nesting_count--;
if (nesting_count > 0) {