【经验之谈】基于STM32G4 SR04超声波模块测距的经验分享

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STMCU小助手发布时间：2022-12-12 14:00

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文章简介:	基于STM32G4 SR04超声波模块测距的经验分享

为了提高测量精度采用平均值滤波经过多次测量提高测量精度。我使用STM32 NUCLEO-G431RB开发板做的，这里使用cubeMX选择该开发板配置

为了省事，我通过串口打印测量结果，板载默认的LPUART1

系统时钟配置为16MHz内部RC振荡器即可

根据时钟设置，定时器使用TIM2，分频为15+1,即可实现计数一次为1us,方便计算。
最大计数可以根据你的需要选择，我这里设置的是50ms的技术周期。这足够测量15米以内的距离了。

为了使用串口printf，我直接复制cubeG4开发包里的例子中的内容

#ifdef __GNUC__
/* With GCC, small printf (option LD Linker->Libraries->Small printf
set to 'Yes') calls __io_putchar() */
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif /* __GNUC__ */
PUTCHAR_PROTOTYPE
{
/* Place your implementation of fputc here */
/* e.g. write a character to the LPUART1 and Loop until the end of transmission */
HAL_UART_Transmit(&hlpuart1, (uint8_t *)&ch, 1, 0xFFFF);
return ch;
}

复制代码

以实现串口printf函数的映射，同时在工程配置中启用MicroLIB即可。
头文件当然要引用一下stdio.h
为了方便代码阅读，对TRIG触发引脚的高低电平设置了如下宏定义。
#include "stdio.h"

#define TRIG_HIGH HAL_GPIO_WritePin(TRIG_GPIO_Port,TRIG_Pin,GPIO_PIN_SET)

#define TRIG_LOW HAL_GPIO_WritePin(TRIG_GPIO_Port,TRIG_Pin,GPIO_PIN_RESET)
并声明了几个变量用于存储临时数据
float t1,t2,temp[5],average,distance;

int i=0;
每个周期的测量会产生两个计数器的值t1,t2,t2-t1时间差就是模块反馈回来的高电平时长，存储到temp数组内，
测完几组数据后计算出时间差的平均值，然后计算长度。循环临时变量为i.

for(i=0;i<5;)
{
htim2.Instance->CNT = 0;
TRIG_LOW;
TRIG_HIGH;
HAL_Delay(1);
TRIG_LOW;
while(HAL_GPIO_ReadPin(ECHO_GPIO_Port,ECHO_Pin)==GPIO_PIN_RESET)
t1=htim2.Instance->CNT;
while(HAL_GPIO_ReadPin(ECHO_GPIO_Port,ECHO_Pin)==GPIO_PIN_SET)
t2=htim2.Instance->CNT;
htim2.Instance->CNT = 0;
if(t2>=t1)
{
temp=t2-t1;
i++;
}
HAL_Delay(50);
}
average=0;
for(i=0;i<5;i++)
average=average+temp;
average=average/5.0;
distance = average*17/1000;
printf("Distance=%.1f cm\n",distance);

复制代码

经过测试，不采用平均值，也是非常准的
唯一的缺点是声波集束度不够好，呈现扇面状，模块传感器与被测物体之间要没有其他障碍物影响，如果没有这些干扰，精度还是非常高的。单次测量即输出数据的完整代码。

/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
*
* 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"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "stdio.h"
#define TRIG_HIGH HAL_GPIO_WritePin(TRIG_GPIO_Port,TRIG_Pin,GPIO_PIN_SET)
#define TRIG_LOW HAL_GPIO_WritePin(TRIG_GPIO_Port,TRIG_Pin,GPIO_PIN_RESET)
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
float t1,t2,temp,distance;
int i=0;
/* 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 ---------------------------------------------------------*/
UART_HandleTypeDef hlpuart1;
TIM_HandleTypeDef htim2;
/* USER CODE BEGIN PV */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_LPUART1_UART_Init(void);
static void MX_TIM2_Init(void);
/* USER CODE BEGIN PFP */
#ifdef __GNUC__
/* With GCC, small printf (option LD Linker->Libraries->Small printf
set to 'Yes') calls __io_putchar() */
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif /* __GNUC__ */
/* 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_LPUART1_UART_Init();
MX_TIM2_Init();
/* USER CODE BEGIN 2 */
if (HAL_UART_Transmit(&hlpuart1, (uint8_t *)"Hello\n", 6, 3000) != HAL_OK)
{
Error_Handler();
}
HAL_TIM_Base_Start(&htim2);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
htim2.Instance->CNT = 0;
TRIG_LOW;
TRIG_HIGH;
HAL_Delay(1);
TRIG_LOW;
while(HAL_GPIO_ReadPin(ECHO_GPIO_Port,ECHO_Pin)==GPIO_PIN_RESET)
t1=htim2.Instance->CNT;
while(HAL_GPIO_ReadPin(ECHO_GPIO_Port,ECHO_Pin)==GPIO_PIN_SET)
t2=htim2.Instance->CNT;
htim2.Instance->CNT = 0;
if(t2>=t1)
{
temp=t2-t1;
}
HAL_Delay(100);
distance = temp*17/1000;
printf("Distance=%.1f cm\n",distance);
HAL_Delay(2000);
/* 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};
RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};
/** Configure the main internal regulator output voltage
*/
HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1);
/** 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();
}
/** Initializes the peripherals clocks
*/
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_LPUART1;
PeriphClkInit.Lpuart1ClockSelection = RCC_LPUART1CLKSOURCE_PCLK1;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief LPUART1 Initialization Function
* @param None
* @retval None
*/
static void MX_LPUART1_UART_Init(void)
{
/* USER CODE BEGIN LPUART1_Init 0 */
/* USER CODE END LPUART1_Init 0 */
/* USER CODE BEGIN LPUART1_Init 1 */
/* USER CODE END LPUART1_Init 1 */
hlpuart1.Instance = LPUART1;
hlpuart1.Init.BaudRate = 115200;
hlpuart1.Init.WordLength = UART_WORDLENGTH_8B;
hlpuart1.Init.StopBits = UART_STOPBITS_1;
hlpuart1.Init.Parity = UART_PARITY_NONE;
hlpuart1.Init.Mode = UART_MODE_TX_RX;
hlpuart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
hlpuart1.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
hlpuart1.Init.ClockPrescaler = UART_PRESCALER_DIV1;
hlpuart1.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
if (HAL_UART_Init(&hlpuart1) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetTxFifoThreshold(&hlpuart1, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetRxFifoThreshold(&hlpuart1, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_DisableFifoMode(&hlpuart1) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN LPUART1_Init 2 */
/* USER CODE END LPUART1_Init 2 */
}
/**
* @brief TIM2 Initialization Function
* @param None
* @retval None
*/
static 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 = 15;
htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
htim2.Init.Period = 49999;
htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
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 */
}
/**
* @brief GPIO Initialization Function
* @param None
* @retval None
*/
static void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOF_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_GPIOB_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(TRIG_GPIO_Port, TRIG_Pin, GPIO_PIN_RESET);
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_RESET);
/*Configure GPIO pin : B1_Pin */
GPIO_InitStruct.Pin = B1_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(B1_GPIO_Port, &GPIO_InitStruct);
/*Configure GPIO pin : TRIG_Pin */
GPIO_InitStruct.Pin = TRIG_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(TRIG_GPIO_Port, &GPIO_InitStruct);
/*Configure GPIO pin : ECHO_Pin */
GPIO_InitStruct.Pin = ECHO_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(ECHO_GPIO_Port, &GPIO_InitStruct);
/*Configure GPIO pin : LD2_Pin */
GPIO_InitStruct.Pin = LD2_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(LD2_GPIO_Port, &GPIO_InitStruct);
}
/* USER CODE BEGIN 4 */
/**
* @brief Retargets the C library printf function to the USART.
* @param None
* @retval None
*/
PUTCHAR_PROTOTYPE
{
/* Place your implementation of fputc here */
/* e.g. write a character to the LPUART1 and Loop until the end of transmission */
HAL_UART_Transmit(&hlpuart1, (uint8_t *)&ch, 1, 0xFFFF);
return ch;
}
/* 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 */
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/