嵌入式-stm32-SR04超声波测距介绍及实战

一：超声波传感器介绍

1.1、SR04超声波测距硬件模块

1.2、SR04的四个IO口

vcc:提供电源5V
gnd:接地
Trig:是**发送**声波信号的触发器
Echo:是**接收**回波信号的引脚
当TRIG信号被触发时，传感器会发送一定频率的声波信号，该信号被反射后，传感器会接收到回波信号，回波信号的时间差可以用来计算物体与传感器的距离。

1.3、SR04是高电平触发模块

所以默认是低电平
怎么让它发送波？
Trig ，给Trig端口至少10us的高电平
怎么知道它开始发了？
Echo信号，由低电平跳转到高电平，表示开始发送波
怎么知道接收了返回波？
Echo，由高电平跳转回低电平，表示波回来了
怎么算时间？
Echo引脚维持高电平的时间！

波发出去的那一下，开始启动定时器
波回来的拿一下，我们开始停止定时器，计算出中间经过多少时间
怎么算距离？
距离 = 速度 （340m/s）* 时间/2

二、需求介绍

2.1、SR04超声波测距需求介绍

需求：使用超声波测距，当手离传感器距离小于5cm时，LED1点亮，否则保持不亮状态。

2.2、SR04超声波测距模块接线
Trig — PB6
Echo — PB7
LED1 — PB8

三：stm32CubeMX实现步骤以及细节

3.1、打开Stm32CubeMX,界面如图

3.2、选芯片：stm32f103c8t6

3.3、读芯片引脚原理图

3.4、先把LED灯设置为高电平模式

3.5、设置时钟

配置时钟频率

3.6、RCC配置

3.7、定时器

计数一次代表1us

Tout就是一次的溢出时间，PSC=71,Tclk=72000 000hz(s),此处ARR=0

3.8、代码自动设置生成的文件

3.9、图形化最后一步

项目名称：sr04_study

四：编写业务代码

4.1、在初始化完成的代码之后添加业务代码

第①处增加的代码：编写微秒级函数

//使用TIM2来做us级延时函数
void TIM2_Delay_us(uint16_t n_us)
{
/* 使能定时器2计数 */
__HAL_TIM_ENABLE(&htim2);
__HAL_TIM_SetCounter(&htim2, 0);
while(__HAL_TIM_GetCounter(&htim2) < ((1 * n_us)-1) );
/* 关闭定时器2计数 */
__HAL_TIM_DISABLE(&htim2);
}

4.2、定义变量

第②处增加的代码

  /* USER CODE BEGIN 1 */int cnt;float distance;/* USER CODE END 1 */

4.3、主函数：

//1. Trig ，给Trig端口至少10us的高电平
//2. echo由低电平跳转到高电平，表示开始发送波
//波发出去的那一下，开始启动定时器
//3. 由高电平跳转回低电平，表示波回来了
//波回来的那一下，我们开始停止定时器
//4. 计算出中间经过多少时间
//5. 距离 = 速度 （340m/s）* 时间/2（注意单位换算）
（计数1次表示1us） //每500毫秒测试一次距离

第③处增加的代码

while (1){/* USER CODE END WHILE *//* USER CODE BEGIN 3 *///1. Trig ，给Trig端口至少10us的高电平HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_SET);//拉高TIM2_Delay_us(20);HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_RESET);//拉低//2. echo由低电平跳转到高电平，表示开始发送波//波发出去的那一下，开始启动定时器while(HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7) == GPIO_PIN_RESET);//等待输入电平拉高HAL_TIM_Base_Start(&htim2);__HAL_TIM_SetCounter(&htim2,0);//3. 由高电平跳转回低电平，表示波回来了while(HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7) == GPIO_PIN_SET);//等待输入电平变低//波回来的那一下，我们开始停止定时器HAL_TIM_Base_Stop(&htim2);//4. 计算出中间经过多少时间cnt = __HAL_TIM_GetCounter(&htim2);//5. 距离 = 速度 （340m/s）* 时间/2（计数1次表示1us）distance = cnt*340/2*0.000001*100; //单位：cm//2*0.000001表示了发送和接收时间的差值（单位为秒）,*100是把米变成厘米if(distance < 5)HAL_GPIO_WritePin(GPIOB, GPIO_PIN_8, GPIO_PIN_RESET);elseHAL_GPIO_WritePin(GPIOB, GPIO_PIN_8, GPIO_PIN_SET);//每500毫秒测试一次距离HAL_Delay(500);}/* USER CODE END 3 */
}

4.4、main.c总代码，直接复制可用

只有main.c有增加，下面的gpio.c、tim.c等等文件都没有变动

/* USER CODE BEGIN Header */
/********************************************************************************* @file           : main.c* @brief          : Main program body******************************************************************************* @attention** Copyright (c) 2023 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 *///使用TIM2来做us级延时函数void TIM2_Delay_us(uint16_t n_us){/* 使能定时器2计数 */__HAL_TIM_ENABLE(&htim2);__HAL_TIM_SetCounter(&htim2, 0);while(__HAL_TIM_GetCounter(&htim2) < ((1 * n_us)-1) );/* 关闭定时器2计数 */__HAL_TIM_DISABLE(&htim2);}
/* USER CODE END 0 *//*** @brief  The application entry point.* @retval int*/
int main(void)
{/* USER CODE BEGIN 1 */int cnt;float distance;/* 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();/* USER CODE BEGIN 2 *//* USER CODE END 2 *//* Infinite loop *//* USER CODE BEGIN WHILE */while (1){/* USER CODE END WHILE *//* USER CODE BEGIN 3 *///1. Trig ，给Trig端口至少10us的高电平HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_SET);//拉高TIM2_Delay_us(20);HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_RESET);//拉低//2. echo由低电平跳转到高电平，表示开始发送波//波发出去的那一下，开始启动定时器while(HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7) == GPIO_PIN_RESET);//等待输入电平拉高HAL_TIM_Base_Start(&htim2);__HAL_TIM_SetCounter(&htim2,0);//3. 由高电平跳转回低电平，表示波回来了while(HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7) == GPIO_PIN_SET);//等待输入电平变低//波回来的那一下，我们开始停止定时器HAL_TIM_Base_Stop(&htim2);//4. 计算出中间经过多少时间cnt = __HAL_TIM_GetCounter(&htim2);//5. 距离 = 速度 （340m/s）* 时间/2（计数1次表示1us）distance = cnt*340/2*0.000001*100; //单位：cm//2*0.000001表示了发送和接收时间的差值（单位为秒）,*100是把米变成厘米if(distance < 5)HAL_GPIO_WritePin(GPIOB, GPIO_PIN_8, GPIO_PIN_RESET);elseHAL_GPIO_WritePin(GPIOB, GPIO_PIN_8, GPIO_PIN_SET);//每500毫秒测试一次距离HAL_Delay(500);}/* 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 */

4.5、gpio.c

/* USER CODE BEGIN Header */
/********************************************************************************* @file    gpio.c* @brief   This file provides code for the configuration*          of all used GPIO pins.******************************************************************************* @attention** Copyright (c) 2023 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 "gpio.h"/* USER CODE BEGIN 0 *//* USER CODE END 0 *//*----------------------------------------------------------------------------*/
/* Configure GPIO                                                             */
/*----------------------------------------------------------------------------*/
/* USER CODE BEGIN 1 *//* USER CODE END 1 *//** Configure pins as* Analog* Input* Output* EVENT_OUT* EXTI
*/
void MX_GPIO_Init(void)
{GPIO_InitTypeDef GPIO_InitStruct = {0};/* GPIO Ports Clock Enable */__HAL_RCC_GPIOD_CLK_ENABLE();__HAL_RCC_GPIOA_CLK_ENABLE();__HAL_RCC_GPIOB_CLK_ENABLE();/*Configure GPIO pin Output Level */HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_RESET);/*Configure GPIO pin Output Level */HAL_GPIO_WritePin(GPIOB, GPIO_PIN_8, GPIO_PIN_SET);/*Configure GPIO pins : PB6 PB8 */GPIO_InitStruct.Pin = GPIO_PIN_6|GPIO_PIN_8;GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;GPIO_InitStruct.Pull = GPIO_NOPULL;GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);/*Configure GPIO pin : PB7 */GPIO_InitStruct.Pin = GPIO_PIN_7;GPIO_InitStruct.Mode = GPIO_MODE_INPUT;GPIO_InitStruct.Pull = GPIO_NOPULL;HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);}/* USER CODE BEGIN 2 *//* USER CODE END 2 */

4.6、tim.c

/* USER CODE BEGIN Header */
/********************************************************************************* @file    tim.c* @brief   This file provides code for the configuration*          of the TIM instances.******************************************************************************* @attention** Copyright (c) 2023 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 "tim.h"/* USER CODE BEGIN 0 *//* USER CODE END 0 */TIM_HandleTypeDef htim2;/* TIM2 init function */
void MX_TIM2_Init(void)
{/* USER CODE BEGIN TIM2_Init 0 *//* USER CODE END TIM2_Init 0 */TIM_ClockConfigTypeDef sClockSourceConfig = {0};TIM_MasterConfigTypeDef sMasterConfig = {0};/* USER CODE BEGIN TIM2_Init 1 *//* USER CODE END TIM2_Init 1 */htim2.Instance = TIM2;htim2.Init.Prescaler = 71;htim2.Init.CounterMode = TIM_COUNTERMODE_UP;htim2.Init.Period = 65535;htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;if (HAL_TIM_Base_Init(&htim2) != HAL_OK){Error_Handler();}sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK){Error_Handler();}sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK){Error_Handler();}/* USER CODE BEGIN TIM2_Init 2 *//* USER CODE END TIM2_Init 2 */}void HAL_TIM_Base_MspInit(TIM_HandleTypeDef* tim_baseHandle)
{if(tim_baseHandle->Instance==TIM2){/* USER CODE BEGIN TIM2_MspInit 0 *//* USER CODE END TIM2_MspInit 0 *//* TIM2 clock enable */__HAL_RCC_TIM2_CLK_ENABLE();/* USER CODE BEGIN TIM2_MspInit 1 *//* USER CODE END TIM2_MspInit 1 */}
}void HAL_TIM_Base_MspDeInit(TIM_HandleTypeDef* tim_baseHandle)
{if(tim_baseHandle->Instance==TIM2){/* USER CODE BEGIN TIM2_MspDeInit 0 *//* USER CODE END TIM2_MspDeInit 0 *//* Peripheral clock disable */__HAL_RCC_TIM2_CLK_DISABLE();/* USER CODE BEGIN TIM2_MspDeInit 1 *//* USER CODE END TIM2_MspDeInit 1 */}
}/* USER CODE BEGIN 1 *//* USER CODE END 1 */

4.7、stm32f1xx_it.c

/* USER CODE BEGIN Header */
/********************************************************************************* @file    stm32f1xx_it.c* @brief   Interrupt Service Routines.******************************************************************************* @attention** Copyright (c) 2023 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 "stm32f1xx_it.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes *//* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN TD *//* USER CODE END TD *//* 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 -----------------------------------------------*/
/* USER CODE BEGIN PFP *//* USER CODE END PFP *//* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 *//* USER CODE END 0 *//* External variables --------------------------------------------------------*//* USER CODE BEGIN EV *//* USER CODE END EV *//******************************************************************************/
/*           Cortex-M3 Processor Interruption and Exception Handlers          */
/******************************************************************************/
/*** @brief This function handles Non maskable interrupt.*/
void NMI_Handler(void)
{/* USER CODE BEGIN NonMaskableInt_IRQn 0 *//* USER CODE END NonMaskableInt_IRQn 0 *//* USER CODE BEGIN NonMaskableInt_IRQn 1 */while (1){}/* USER CODE END NonMaskableInt_IRQn 1 */
}/*** @brief This function handles Hard fault interrupt.*/
void HardFault_Handler(void)
{/* USER CODE BEGIN HardFault_IRQn 0 *//* USER CODE END HardFault_IRQn 0 */while (1){/* USER CODE BEGIN W1_HardFault_IRQn 0 *//* USER CODE END W1_HardFault_IRQn 0 */}
}/*** @brief This function handles Memory management fault.*/
void MemManage_Handler(void)
{/* USER CODE BEGIN MemoryManagement_IRQn 0 *//* USER CODE END MemoryManagement_IRQn 0 */while (1){/* USER CODE BEGIN W1_MemoryManagement_IRQn 0 *//* USER CODE END W1_MemoryManagement_IRQn 0 */}
}/*** @brief This function handles Prefetch fault, memory access fault.*/
void BusFault_Handler(void)
{/* USER CODE BEGIN BusFault_IRQn 0 *//* USER CODE END BusFault_IRQn 0 */while (1){/* USER CODE BEGIN W1_BusFault_IRQn 0 *//* USER CODE END W1_BusFault_IRQn 0 */}
}/*** @brief This function handles Undefined instruction or illegal state.*/
void UsageFault_Handler(void)
{/* USER CODE BEGIN UsageFault_IRQn 0 *//* USER CODE END UsageFault_IRQn 0 */while (1){/* USER CODE BEGIN W1_UsageFault_IRQn 0 *//* USER CODE END W1_UsageFault_IRQn 0 */}
}/*** @brief This function handles System service call via SWI instruction.*/
void SVC_Handler(void)
{/* USER CODE BEGIN SVCall_IRQn 0 *//* USER CODE END SVCall_IRQn 0 *//* USER CODE BEGIN SVCall_IRQn 1 *//* USER CODE END SVCall_IRQn 1 */
}/*** @brief This function handles Debug monitor.*/
void DebugMon_Handler(void)
{/* USER CODE BEGIN DebugMonitor_IRQn 0 *//* USER CODE END DebugMonitor_IRQn 0 *//* USER CODE BEGIN DebugMonitor_IRQn 1 *//* USER CODE END DebugMonitor_IRQn 1 */
}/*** @brief This function handles Pendable request for system service.*/
void PendSV_Handler(void)
{/* USER CODE BEGIN PendSV_IRQn 0 *//* USER CODE END PendSV_IRQn 0 *//* USER CODE BEGIN PendSV_IRQn 1 *//* USER CODE END PendSV_IRQn 1 */
}/*** @brief This function handles System tick timer.*/
void SysTick_Handler(void)
{/* USER CODE BEGIN SysTick_IRQn 0 *//* USER CODE END SysTick_IRQn 0 */HAL_IncTick();/* USER CODE BEGIN SysTick_IRQn 1 *//* USER CODE END SysTick_IRQn 1 */
}/******************************************************************************/
/* STM32F1xx Peripheral Interrupt Handlers                                    */
/* Add here the Interrupt Handlers for the used peripherals.                  */
/* For the available peripheral interrupt handler names,                      */
/* please refer to the startup file (startup_stm32f1xx.s).                    */
/******************************************************************************//* USER CODE BEGIN 1 *//* USER CODE END 1 */

4.8、超声波测距效果

1.代码编译，烧录之后
2.测试超声波测距
把手放在距离sr04 5cm以内，led灯会亮，再远灯会灭

以上，完