在stm32的freeRTOS上进行微秒级延时(HAL库)

最新推荐文章于 2025-07-03 16:53:23 发布

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#stm32 #hal #freeRTOS #单片机 #嵌入式

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本文介绍了一种在STM32上实现微秒级延时的方法，利用DWT模块提供精确的时间延迟，适用于FreeRTOS环境下需要高精度延时的应用场景。

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因为时间片的原因freeRTOS自身貌似无法进行微秒级的延时,实测通过以下函数可以进行微秒级的消息

dwt_stm32_delay.h

#ifndef DWT_STM32_DELAY_H
#define DWT_STM32_DELAY_H

#ifdef __cplusplus
extern "C" {
#endif

#include "stm32f4xx_hal.h"

/**
 * @brief  Initializes DWT_Cycle_Count for DWT_Delay_us function
 * @return Error DWT counter
 *         1: DWT counter Error
 *         0: DWT counter works
 */
uint32_t DWT_Delay_Init(void);

/**
 * @brief  This function provides a delay (in microseconds)
 * @param  microseconds: delay in microseconds
 */
__STATIC_INLINE void DWT_Delay_us(volatile uint32_t microseconds)
{
  uint32_t clk_cycle_start = DWT->CYCCNT;

  /* Go to number of cycles for system */
  microseconds *= (HAL_RCC_GetHCLKFreq() / 1000000);

  /* Delay till end */
  while ((DWT->CYCCNT - clk_cycle_start) < microseconds);
}

#ifdef __cplusplus
}
#endif

#endif

dwt_stm32_delay.c

#include "dwt_stm32_delay.h"

/**
 * @brief  Initializes DWT_Clock_Cycle_Count for DWT_Delay_us function
 * @return Error DWT counter
 *         1: clock cycle counter not started
 *         0: clock cycle counter works
 */
uint32_t DWT_Delay_Init(void) {
  /* Disable TRC */
  CoreDebug->DEMCR &= ~CoreDebug_DEMCR_TRCENA_Msk; // ~0x01000000;
  /* Enable TRC */
  CoreDebug->DEMCR |=  CoreDebug_DEMCR_TRCENA_Msk; // 0x01000000;

  /* Disable clock cycle counter */
  DWT->CTRL &= ~DWT_CTRL_CYCCNTENA_Msk; //~0x00000001;
  /* Enable  clock cycle counter */
  DWT->CTRL |=  DWT_CTRL_CYCCNTENA_Msk; //0x00000001;

  /* Reset the clock cycle counter value */
  DWT->CYCCNT = 0;

     /* 3 NO OPERATION instructions */
     __ASM volatile ("NOP");
     __ASM volatile ("NOP");
  __ASM volatile ("NOP");

  /* Check if clock cycle counter has started */
     if(DWT->CYCCNT)
     {
       return 0; /*clock cycle counter started*/
     }
     else
  {
    return 1; /*clock cycle counter not started*/
  }
}

main.c

/* Includes ------------------------------------------------------------------*/
#include "stm32f4xx_hal.h"
#include "dwt_stm32_delay.h"

int main(void)
{
  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration----------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

  /* Initialize all configured peripherals */
  MX_GPIO_Init();

  /* USER CODE BEGIN 2 */

  if(DWT_Delay_Init())
  {
    Error_Handler(); /* Call Error Handler */
  }

  while(1)
  {
    /* 10s Delay */
    DWT_Delay_us(10000000);

    HAL_GPIO_TogglePin(LD2_GPIO_Port, LD2_Pin);
  }
}