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cm
            printf("\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_9

void 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