STM32 HAL library for HC-SR04 ultrasonic sensor

A simple library for HC-SR04 ultrasonic sensor. It uses STM32 HAL library.

Copy the library header and source files to your project folder(Inc and Src folders).

Usage

Configure STM32CubeMX to use GPIO pins for trigger pin, use TIM input capture mode for echo pin.

In this example, I used PA9 for trigger pin and TIM1 CH1(PA8) for echo pin.

Set timer prescaler to 72, use internal clock source.

Set channel 1 to input capture mode, set polarity to rising edge.

Enable interrupt in NVIC settings.

Include the header file in your main.h file.

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "sr04.h"
/* USER CODE END Includes */

Declare the sensor struct in your main.c file.

/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
sr04_t sr04;
/* USER CODE END PV */

Configure the sensor struct and initialize the sensor.

  /* USER CODE BEGIN 2 */
  sr04.trig_port = GPIOA;
  sr04.trig_pin = GPIO_PIN_9;
  sr04.echo_htim = &htim1;
  sr04.echo_channel = TIM_CHANNEL_1;
  sr04_init(&sr04);
  /* USER CODE END 2 */

Trigger the sensor in main loop.

  /* USER CODE BEGIN WHILE */
  while (1)
  {
    sr04_trigger(&sr04);
    HAL_Delay(100);
    printf("Distance: %lu mm\r\n", sr04.distance);
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */

In stm32f1xx_it.c file, use extern to import the sensor struct.

/* USER CODE BEGIN EV */
extern sr04_t sr04;
/* USER CODE END EV */

Increase the update count in timer interrupt callback function. This is used to calibrate the distance.

void TIM1_UP_IRQHandler(void)
{
  /* USER CODE BEGIN TIM1_UP_IRQn 0 */
  // Update interrupt handling
  if (__HAL_TIM_GET_FLAG(sr04.echo_htim, TIM_FLAG_UPDATE) != RESET)
  {
      if (__HAL_TIM_GET_IT_SOURCE(sr04.echo_htim, TIM_IT_UPDATE) != RESET)
      {
          sr04.tim_update_count++;
      }
  }
  /* USER CODE END TIM1_UP_IRQn 0 */
  HAL_TIM_IRQHandler(&htim1);
  /* USER CODE BEGIN TIM1_UP_IRQn 1 */

  /* USER CODE END TIM1_UP_IRQn 1 */
}

Replace TIM_FLAG_CC1 and TIM_IT_CC1 to actual capture channel number.

Read the distance in timer interrupt callback function.

void TIM1_CC_IRQHandler(void)
{
  /* USER CODE BEGIN TIM1_CC_IRQn 0 */
  // Capture interrupt handling
  if (__HAL_TIM_GET_FLAG(&htim1, TIM_FLAG_CC1) != RESET)
  {
      if (__HAL_TIM_GET_IT_SOURCE(&htim1, TIM_IT_CC1) != RESET)
      {
          sr04_read_distance(&sr04);
      }
  }
  /* USER CODE END TIM1_CC_IRQn 0 */
  HAL_TIM_IRQHandler(&htim1);
  /* USER CODE BEGIN TIM1_CC_IRQn 1 */

  /* USER CODE END TIM1_CC_IRQn 1 */
}

The distance will be stored in sr04.distance variable, the unit is mm.

---

General purpose timer version:

void TIM4_IRQHandler(void)
{
  /* USER CODE BEGIN TIM4_IRQn 0 */
  // Capture interrupt handling
  if (__HAL_TIM_GET_FLAG(&htim4, TIM_FLAG_CC1) != RESET)
  {
      if (__HAL_TIM_GET_IT_SOURCE(&htim4, TIM_IT_CC1) != RESET)
      {
          sr04_read_distance(&sr04);
      }
  }
  // Update interrupt handling
  if (__HAL_TIM_GET_FLAG(&htim4, TIM_FLAG_UPDATE) != RESET)
  {
      if (__HAL_TIM_GET_IT_SOURCE(&htim4, TIM_IT_UPDATE) != RESET)
      {
          sr04.tim_update_count++;
      }
  }
  /* USER CODE END TIM4_IRQn 0 */
  HAL_TIM_IRQHandler(&htim4);
  /* USER CODE BEGIN TIM4_IRQn 1 */

  /* USER CODE END TIM4_IRQn 1 */
}

Multiple sensor instances

You can use multiple sensor instances by declaring and configuring multiple sensor structs.

Interrupt callback function:

void TIM4_IRQHandler(void)
{
  /* USER CODE BEGIN TIM4_IRQn 0 */
    // Capture interrupt handling
    if (__HAL_TIM_GET_FLAG(&htim4, TIM_FLAG_CC1) != RESET)
    {
        if (__HAL_TIM_GET_IT_SOURCE(&htim4, TIM_IT_CC1) != RESET)
        {
            sr04_read_distance(&sr04_1);
        }
    }
    if (__HAL_TIM_GET_FLAG(&htim4, TIM_FLAG_CC2) != RESET)
    {
        if (__HAL_TIM_GET_IT_SOURCE(&htim4, TIM_IT_CC2) != RESET)
        {
            sr04_read_distance(&sr04_2);
        }
    }
    // Update interrupt handling
    if (__HAL_TIM_GET_FLAG(&htim4, TIM_FLAG_UPDATE) != RESET)
    {
        if (__HAL_TIM_GET_IT_SOURCE(&htim4, TIM_IT_UPDATE) != RESET)
        {
            sr04_1.tim_update_count++;
            sr04_2.tim_update_count++;
        }
    }
  /* USER CODE END TIM4_IRQn 0 */
  HAL_TIM_IRQHandler(&htim4);
  /* USER CODE BEGIN TIM4_IRQn 1 */

  /* USER CODE END TIM4_IRQn 1 */
}