一HC-SR04介绍

1HC-SR04简介及工作原理

超声波是振动频率高于20kHz的机械波。它具有频率高、波长短、绕射现象小、方向性好、能够成为射线而定向传播等特点。HC-SRO4是一款尺寸完全兼容老版本，增加UART和IIC功能的开放式超声波测距模块,默认条件下,软件与硬件完全兼容老版本HC-SRO4;可以通过电阻设置成UART或IIC模式。2CM盲区,4.5M典型最远测距，2.2mA作电流。采用升级解调芯片RCWL-9206,带UART与IIC功能MCU:使其外围更加简洁,工作电压更宽(3-5.5V),接口功能更多。

工作原理：

(1)采用 IO 口 TRIG 触发测距，给最少 10us 的高电平信呈。
(2)模块自动发送 8 个 40khz 的方波，自动检测是否有信号返回。
(3)有信号返回，通过 IO 口 ECHO 输出一个高电平，高电平持续的时间就是超声
波从发射到返回的时间。测试距离=(高电平时间*声速(340M/S))/2。

二用HAL库实现HC-SR04测量距离

本文使用的MCU为STM32F103C8T6。

1STM32CubeMX配置

1创建一个工程

2RCC

3SYS

4时钟树

5GPIO

6串口1

7定时器2

8开启定时器中断

2keil5

1勾选Use MicroLiB

2创建SR04.c和SR04.h文件

3创建led.c和led.h文件

3代码的添加

main.

/* USER CODE BEGIN Header */
/********************************************************************************* @file           : main.c* @brief          : Main program body******************************************************************************* @attention** <h2><center>&copy; Copyright (c) 2022 STMicroelectronics.* All rights reserved.</center></h2>** This software component is licensed by ST under BSD 3-Clause license,* the "License"; You may not use this file except in compliance with the* License. You may obtain a copy of the License at:*                        opensource.org/licenses/BSD-3-Clause********************************************************************************/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "tim.h"
#include "usart.h"
#include "gpio.h"/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "SR04.h"
#include "led.h"
/* 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_TIM2_Init();MX_USART1_UART_Init();/* USER CODE BEGIN 2 *//* USER CODE END 2 *//* Infinite loop *//* USER CODE BEGIN WHILE */while (1){float distance = SR04_GetData();//HAL_Delay(1500);/* USER CODE END WHILE */// 根据距离计算闪烁频率uint32_t flashRate = CalculateFlashRate(distance);LED_Flash(flashRate); // 闪烁LED/* 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_HSE;RCC_OscInitStruct.HSEState = RCC_HSE_ON;RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;RCC_OscInitStruct.HSIState = RCC_HSI_ON;RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;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_PLLCLK;RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != 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 */

SR04.c

#include "SR04.h"
#include "stm32f1xx_hal.h" float distant;      //测量距离
uint32_t measure_Buf[3] = {0};   //存放定时器计数值的数组
uint8_t  measure_Cnt = 0;    //状态标志位
uint32_t high_time;   //超声波模块返回的高电平时间//===============================================读取距离
float SR04_GetData(void)
{switch (measure_Cnt){case 0:TRIG_H;delay_us(30);TRIG_L;measure_Cnt++;__HAL_TIM_SET_CAPTUREPOLARITY(&htim2, TIM_CHANNEL_1, TIM_INPUTCHANNELPOLARITY_RISING);HAL_TIM_IC_Start_IT(&htim2, TIM_CHANNEL_1); // 启动输入捕获break;case 3:high_time = measure_Buf[1] - measure_Buf[0]; // 高电平时间printf("\r\n----高电平时间-%d-us----\r\n", high_time);float distance = (high_time * 0.034f) / 2; // 单位cmprintf("\r\n-检测距离为-%.2f-cm-\r\n", distance);measure_Cnt = 0; // 清空标志位TIM2->CNT = 0; // 清空计时器计数// 返回计算得到的距离值return distance;}return 0; // 如果没有测量完成，返回0或合适的默认值
}//===============================================us延时函数void delay_us(uint32_t us)//主频72M
{uint32_t delay = (HAL_RCC_GetHCLKFreq() / 4000000 * us);while (delay--){;}
}//===============================================中断回调函数
void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim)//
{if(TIM2 == htim->Instance)// 判断触发的中断的定时器为TIM2{switch(measure_Cnt){case 1:measure_Buf[0] = HAL_TIM_ReadCapturedValue(&htim2,TIM_CHANNEL_1);//获取当前的捕获值.__HAL_TIM_SET_CAPTUREPOLARITY(&htim2,TIM_CHANNEL_1,TIM_ICPOLARITY_FALLING);  //设置为下降沿捕获measure_Cnt++;                                            break;              case 2:measure_Buf[1] = HAL_TIM_ReadCapturedValue(&htim2,TIM_CHANNEL_1);//获取当前的捕获值.HAL_TIM_IC_Stop_IT(&htim2,TIM_CHANNEL_1); //停止捕获   或者: __HAL_TIM_DISABLE(&htim5);measure_Cnt++;  }}}

SR04.h

#ifndef __SR04_H
#define __SR04_H
#include "main.h"
#include "tim.h"
#include "stdio.h"#define TRIG_H  HAL_GPIO_WritePin(Trig_GPIO_Port,Trig_Pin,GPIO_PIN_SET)
#define TRIG_L  HAL_GPIO_WritePin(Trig_GPIO_Port,Trig_Pin,GPIO_PIN_RESET)void delay_us(uint32_t us);
float SR04_GetData(void);#endif

led.c

#include "led.h"#define LED_GPIO_Port       GPIOB
#define LED_Pin             GPIO_PIN_9void LED_Init(void) {GPIO_InitTypeDef GPIO_InitStruct = {0};// 使能GPIOB时钟__HAL_RCC_GPIOB_CLK_ENABLE();// 配置GPIO Pin为推挽输出，无上拉电阻，低频率GPIO_InitStruct.Pin = LED_Pin;GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;GPIO_InitStruct.Pull = GPIO_NOPULL;GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;HAL_GPIO_Init(LED_GPIO_Port, &GPIO_InitStruct);
}void LED_Flash(uint32_t period) {// 切换LED状态HAL_GPIO_TogglePin(LED_GPIO_Port, LED_Pin);// 延时HAL_Delay(period);// 再次切换LED状态，完成一次闪烁HAL_GPIO_TogglePin(LED_GPIO_Port, LED_Pin);
}uint32_t CalculateFlashRate(float distance) {uint32_t flashRate;if (distance < 10.0f) {flashRate = 100; // 距离小于10厘米时，快速闪烁} else if (distance < 50.0f) {flashRate = 500; // 距离在10-50厘米之间时，中速闪烁} else {flashRate = 1000; // 距离大于50厘米时，慢速闪烁}return flashRate;
}

led.h

#ifndef __LED_H__
#define __LED_H__#include "stm32f1xx_hal.h"void LED_Init(void);
void LED_Flash(uint32_t period); 
uint32_t CalculateFlashRate(float distance);#endif // __LED_H__

三效果

led灯可以随着HC-SR04测量到的距离变化而改变闪烁的频率