一、原理
本次实验采用HC-SR04超声波传感器，结构及功能如下图
超声波传感器可以用来测距。距离 = 声速（340m/s) *传播时间 / 2。
这个传感器有四个引脚，其中VCC接电源正极，GND接电源负极 ， Trig : 用来启动测量 ，Echo用来返回结果。
在开始测量之前，我们要给Trig引脚施加一个大于10微秒的脉冲，然后T开始发送超声波，整个过程大约持续0.2毫秒，声波发送结束后Echo引脚上会出现一个上升沿，然后当8个周期 的超声波全部接收到后，Echo引脚上又会出现一个下降沿。这样在Echo引脚上就形成了一个脉冲，我们测量脉冲的宽度就能得到超声波在空气中传播的时间。
二、STM32CubeMX配置
1：设置调试接口
2：设置PA0
3：设置定时器——通道一选择上升沿直接，通道二选择下降沿间接
4：配置板载LED：PC13引脚
接下来用几张图回顾一下定时器的工作过程
分辨率：
所以
5：设置定时器参数
6：保存并且打开工程
三、电路连接图
四、编程接口
HAL_StatusTypeDef HAL_TIM_IC_Start(TIM_HandleTypeDef *htim , uint32_t Channel)作用 ：启动输入捕获HAL_StatusTypeDef HAL_TIM_IC_Stop(TIM_HandleTypeDef *htim , uint32_t Channel)作用 ：停止输入捕获参数说明：htim ：定时器句柄指针Channel ： 通道编号五、编程思路
1：让CNT的值归0
2：清除CCR1和CCR2标志位
CNT溢出时，会触发update，当update发生的时候，单片机会自动让update标志位从0到1；所以我们只需要查询一下update的标志位就可以知道CNT有没有溢出。当我们把定时器通道设置为输入捕获模式，当这些通道捕捉到了对应的信号变化时就会产生一个CCx时间，单片机会自动的将CCx标志位从0变到1，所以我们只需要查询一下CCx标注位就可以知道这个通道当前有没有捕捉到信号变化。在使用之前需要对其清0。
3：启动定时器
4：向Trig引脚发送脉冲：
向PA0写1
延迟
向PA0写0
5：等待测量结束
CC1标志位从0变到1——捕获到了上升沿
CC2的标志位从0变到1 ——捕获到了下降沿
__HAL_TIM_GET_FLAG(__HANDLE__,__FLAG__)
返回值0——标志位等于0
返回值非零——标志位等于1
6：关闭定时器
7：计算测量结果
uint16_t ccr1 = __HAL_TIM_GET_COMPARE(&htim1 , TIM_CHANNEL_1); //计算CCR1的值
uint16_t ccr2 = __HAL_TIM_GET_COMPARE(&htim1 , TIM_CHANNEL_2); //计算CCR2的值
float pulseWidth = (cc1 - ccr2) *1e-6f;
float distance = 340.0f *pulseWidth / 2.0f;
8:通过判断距离点亮/熄灭板载LED
六、代码
/* USER CODE BEGIN Header */
/********************************************************************************* @file : main.c* @brief : Main program body******************************************************************************* @attention** Copyright (c) 2025 STMicroelectronics.* All rights reserved.** This software is licensed under terms that can be found in the LICENSE file* in the root directory of this software component.* If no LICENSE file comes with this software, it is provided AS-IS.********************************************************************************/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "tim.h"
#include "gpio.h"/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes *//* USER CODE END Includes *//* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD *//* USER CODE END PTD *//* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD *//* USER CODE END PD *//* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM *//* USER CODE END PM *//* Private variables ---------------------------------------------------------*//* USER CODE BEGIN PV *//* USER CODE END PV *//* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP *//* USER CODE END PFP *//* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 *//* USER CODE END 0 *//*** @brief The application entry point.* @retval int*/
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();/* USER CODE BEGIN Init *//* USER CODE END Init *//* Configure the system clock */SystemClock_Config();/* USER CODE BEGIN SysInit *//* USER CODE END SysInit *//* Initialize all configured peripherals */MX_GPIO_Init();MX_TIM1_Init();/* USER CODE BEGIN 2 *//* USER CODE END 2 *//* Infinite loop *//* USER CODE BEGIN WHILE */while (1){//1.让计数器CNT归零__HAL_TIM_SET_COUNTER(&htim1 , 0);//2.清除CC1/CC2的标志位__HAL_TIM_CLEAR_FLAG(&htim1 , TIM_FLAG_CC1);__HAL_TIM_CLEAR_FLAG(&htim1 , TIM_FLAG_CC2);//3.启动输入捕获HAL_TIM_IC_Start(&htim1 , TIM_CHANNEL_1);HAL_TIM_IC_Start(&htim1 , TIM_CHANNEL_2);//4.向Trig发送脉冲HAL_GPIO_WritePin(GPIOA , GPIO_PIN_0 , GPIO_PIN_SET);for (uint32_t i = 0 ; i < 10 ; i++);HAL_GPIO_WritePin(GPIOA , GPIO_PIN_0 , GPIO_PIN_RESET);//5.等待测量结束uint8_t success = 0;uint32_t expireTime = HAL_GetTick() + 50 ; //计算超时时间while(expireTime > HAL_GetTick()) //判断是否超时{uint32_t cc1Flag = __HAL_TIM_GET_FLAG(&htim1,TIM_FLAG_CC1); //CC1标志位uint32_t cc2Flag = __HAL_TIM_GET_FLAG(&htim1,TIM_FLAG_CC2); //CC2标志位if (cc1Flag && cc2Flag ){success = 1 ;break;}}//6.关闭定时器HAL_TIM_IC_Stop(&htim1 , TIM_CHANNEL_1); HAL_TIM_IC_Stop(&htim1 , TIM_CHANNEL_1);//7.计算测量结果if(success == 1){uint16_t ccr1 = __HAL_TIM_GET_COMPARE(&htim1 , TIM_CHANNEL_1); //计算CCR1的值uint16_t ccr2 = __HAL_TIM_GET_COMPARE(&htim1 , TIM_CHANNEL_2);//计算CCR2的值float pulseWidth = (ccr1 - ccr2) *1e-6f; //计算脉宽 秒 = 微秒 * 1e-6float distance = 340.0f *pulseWidth / 2.0f; //计算距离 if(distance < 0.2) //距离是否小于0.2米{HAL_GPIO_WritePin(GPIOC , GPIO_PIN_13 , GPIO_PIN_RESET); //点亮板载LED}else {HAL_GPIO_WritePin(GPIOC , GPIO_PIN_13 , GPIO_PIN_SET); //熄灭板载LED}}/* USER CODE END WHILE *//* USER CODE BEGIN 3 */}/* USER CODE END 3 */
}/*** @brief System Clock Configuration* @retval None*/
void SystemClock_Config(void)
{RCC_OscInitTypeDef RCC_OscInitStruct = {0};RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};/** Initializes the RCC Oscillators according to the specified parameters* in the RCC_OscInitTypeDef structure.*/RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;RCC_OscInitStruct.HSIState = RCC_HSI_ON;RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK){Error_Handler();}/** Initializes the CPU, AHB and APB buses clocks*/RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK){Error_Handler();}
}/* USER CODE BEGIN 4 *//* USER CODE END 4 *//*** @brief This function is executed in case of error occurrence.* @retval None*/
void Error_Handler(void)
{/* USER CODE BEGIN Error_Handler_Debug *//* User can add his own implementation to report the HAL error return state */__disable_irq();while (1){}/* USER CODE END Error_Handler_Debug */
}#ifdef USE_FULL_ASSERT
/*** @brief Reports the name of the source file and the source line number* where the assert_param error has occurred.* @param file: pointer to the source file name* @param line: assert_param error line source number* @retval None*/
void assert_failed(uint8_t *file, uint32_t line)
{/* USER CODE BEGIN 6 *//* User can add his own implementation to report the file name and line number,ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) *//* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
最后将代码下载编译，就可以看到当物体距离超声波传感器0.2m以内时板载LED点亮，大于0.2米时板载LED熄灭。