1960475ed7
pyb.delay and pyb.udelay now use systick if IRQs are enabled, otherwise they use a busy loop. Thus they work correctly when IRQs are disabled. The busy loop is computed from the current CPU frequency, so works no matter the CPU frequency.
119 lines
4.8 KiB
C
119 lines
4.8 KiB
C
/*
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* This file is part of the Micro Python project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2013, 2014 Damien P. George
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <stm32f4xx_hal.h>
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#include "mpconfig.h"
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#include "misc.h"
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#include "nlr.h"
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#include "qstr.h"
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#include "obj.h"
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#include "irq.h"
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#include "systick.h"
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// We provide our own version of HAL_Delay that calls __WFI while waiting, in
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// order to reduce power consumption.
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void HAL_Delay(uint32_t Delay) {
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if (query_irq() == IRQ_STATE_ENABLED) {
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// IRQs enabled, so can use systick counter to do the delay
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extern __IO uint32_t uwTick;
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uint32_t start = uwTick;
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// Wraparound of tick is taken care of by 2's complement arithmetic.
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while (uwTick - start < Delay) {
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// Enter sleep mode, waiting for (at least) the SysTick interrupt.
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__WFI();
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}
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} else {
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// IRQs disabled, so need to use a busy loop for the delay.
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// To prevent possible overflow of the counter we use a double loop.
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const uint32_t count_1ms = HAL_RCC_GetSysClockFreq() / 4000;
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for (int i = 0; i < Delay; i++) {
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for (uint32_t count = 0; ++count <= count_1ms;) {
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}
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}
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}
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}
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// delay for given number of microseconds
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void sys_tick_udelay(uint32_t usec) {
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if (query_irq() == IRQ_STATE_ENABLED) {
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// IRQs enabled, so can use systick counter to do the delay
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uint32_t start = sys_tick_get_microseconds();
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while (sys_tick_get_microseconds() - start < usec) {
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}
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} else {
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// IRQs disabled, so need to use a busy loop for the delay
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// sys freq is always a multiple of 2MHz, so division here won't lose precision
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const uint32_t ucount = HAL_RCC_GetSysClockFreq() / 2000000 * usec / 2;
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for (uint32_t count = 0; ++count <= ucount;) {
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}
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}
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}
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bool sys_tick_has_passed(uint32_t start_tick, uint32_t delay_ms) {
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return HAL_GetTick() - start_tick >= delay_ms;
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}
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// waits until at least delay_ms milliseconds have passed from the sampling of
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// startTick. Handles overflow properly. Assumes stc was taken from
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// HAL_GetTick() some time before calling this function.
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void sys_tick_wait_at_least(uint32_t start_tick, uint32_t delay_ms) {
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while (!sys_tick_has_passed(start_tick, delay_ms)) {
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__WFI(); // enter sleep mode, waiting for interrupt
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}
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}
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// The SysTick timer counts down at 168 MHz, so we can use that knowledge
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// to grab a microsecond counter.
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//
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// We assume that HAL_GetTickis returns milliseconds.
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uint32_t sys_tick_get_microseconds(void) {
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mp_uint_t irq_state = disable_irq();
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uint32_t counter = SysTick->VAL;
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uint32_t milliseconds = HAL_GetTick();
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uint32_t status = SysTick->CTRL;
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enable_irq(irq_state);
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// It's still possible for the countflag bit to get set if the counter was
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// reloaded between reading VAL and reading CTRL. With interrupts disabled
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// it definitely takes less than 50 HCLK cycles between reading VAL and
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// reading CTRL, so the test (counter > 50) is to cover the case where VAL
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// is +ve and very close to zero, and the COUNTFLAG bit is also set.
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if ((status & SysTick_CTRL_COUNTFLAG_Msk) && counter > 50) {
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// This means that the HW reloaded VAL between the time we read VAL and the
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// time we read CTRL, which implies that there is an interrupt pending
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// to increment the tick counter.
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milliseconds++;
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}
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uint32_t load = SysTick->LOAD;
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counter = load - counter; // Convert from decrementing to incrementing
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// ((load + 1) / 1000) is the number of counts per microsecond.
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//
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// counter / ((load + 1) / 1000) scales from the systick clock to microseconds
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// and is the same thing as (counter * 1000) / (load + 1)
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return milliseconds * 1000 + (counter * 1000) / (load + 1);
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}
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