74 lines
2.1 KiB
C
74 lines
2.1 KiB
C
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/*
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* Simple microseconds delay routine, utilizing ARM's DWT
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* (Data Watchpoint and Trace Unit) and HAL library.
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* Intended to use with gcc compiler, but I hope it can be used
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* with any other C compiler across the Universe (provided that
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* ARM and CMSIS already invented) :)
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* Max K
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*
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*
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* This file is part of DWT_Delay package.
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* DWT_Delay is free software: you can redistribute it and/or modify it
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* under the terms of the MIT License
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*/
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// #include "stm32f1xx_hal.h" // change to whatever MCU or Cortex-M core you use
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#include "dwt_delay.h"
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#include "at32f403a_407.h" // CMSIS header
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/**
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* Initialization routine.
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* You might need to enable access to DWT registers on Cortex-M7
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* DWT->LAR = 0xC5ACCE55
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*/
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void DWT_Init(void)
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{
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if (!(CoreDebug->DEMCR & CoreDebug_DEMCR_TRCENA_Msk)) {
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CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
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DWT->CYCCNT = 0;
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DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
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}
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}
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#if DWT_DELAY_NEWBIE
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/**
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* If you are a newbie and see magic in DWT_Delay, consider this more
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* illustrative function, where you explicitly determine a counter
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* value when delay should stop while keeping things in bounds of uint32.
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*
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* @param uint32_t us Number of microseconds to delay for
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*/
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void DWT_Delay(uint32_t us)
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{
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uint32_t startTick = DWT->CYCCNT,
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targetTick = DWT->CYCCNT + us * (SystemCoreClock/1000000);
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// Must check if target tick is out of bounds and overflowed
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if (targetTick > startTick) {
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// Not overflowed
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while (DWT->CYCCNT < targetTick);
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} else {
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// Overflowed
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while (DWT->CYCCNT > startTick || DWT->CYCCNT < targetTick);
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}
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}
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#else
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/**
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* Delay routine itself.
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* Time is in microseconds (1/1000000th of a second), not to be
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* confused with millisecond (1/1000th).
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*
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* No need to check an overflow. Let it just tick :)
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*
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* @param uint32_t us Number of microseconds to delay for
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*/
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void DWT_Delay(uint32_t us)
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{
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uint32_t startTick = DWT->CYCCNT,
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delayTicks = us * (SystemCoreClock/1000000);
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while (DWT->CYCCNT - startTick < delayTicks);
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}
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#endif
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