一.任务需求
1. 采用stm32F103和HC-SR04超声波模块, 使用标准库或HAL库+ 定时器中断,完成1或2路的超声波障碍物测距功能。
2. 当前智能汽车上一般配置有12路超声波雷达,这些专用超声波雷达内置了MCU,直接输出数字化的测距结果,一般硬件接口采用串口RS485,通信协议采用modbus。请思考:
-
RS485与RS232(UART)有什么不同?
-
Modbus协议是什么?
-
如果让你设计一款 12路车载超声波雷达,采用 stm32F103+HC-SR04超声波模块,对外提供RS485和Modbus协议,你的设计方案是什么?
二.超声波测距实验过程
1.创建项目
设置sys
设置rcc
定时器tim2设置
定时器tim3设置
gpio管脚设置:
之后导入RTthread,导入过程参考:https://blog.csdn.net/lxr0106/article/details/134635908
2.编写代码
SC04.h:
c
#ifndef __SR04_H
#define __SR04_H
#include "main.h"
#include "tim.h"
#include "stdio.h"
#include "rtthread.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)
extern float distant;
void delay_us(uint32_t us);
void SR04_GetData(void);
void rt_hw_us_delay(rt_uint32_t us);
#endif
SC04.c:
c
#include "SR04.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
void SR04_GetData(void)
{
switch (measure_Cnt){
case 0:
TRIG_H;
rt_hw_us_delay(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 或者: __HAL_TIM_ENABLE(&htim5);
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);
distant=(high_time*0.034)/2; //单位cm
printf("\r\n-检测距离为-%.2f-cm-\r\n",distant);
measure_Cnt = 0; //清空标志位
TIM2->CNT=0; //清空计时器计数
break;
}
}
//===============================================us延时函数
void delay_us(uint32_t us)//主频72M
{
uint32_t delay = (HAL_RCC_GetHCLKFreq() / 4000000 * us);
while (delay--)
{
;
}
}
void rt_hw_us_delay(rt_uint32_t us)
{
rt_uint32_t ticks;
rt_uint32_t told, tnow, tcnt = 0;
rt_uint32_t reload = SysTick->LOAD;
/* 获得延时经过的 tick 数 */
ticks = us * reload / (1000000 / RT_TICK_PER_SECOND);
/* 获得当前时间 */
told = SysTick->VAL;
while (1)
{
/* 循环获得当前时间,直到达到指定的时间后退出循环 */
tnow = SysTick->VAL;
if (tnow != told)
{
if (tnow < told)
{
tcnt += told - tnow;
}
else
{
tcnt += reload - tnow + told;
}
told = tnow;
if (tcnt >= ticks)
{
break;
}
}
}
}
//===============================================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++;
}
}
}
main.c:
c
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* <h2><center>© 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 <rtthread.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();
MX_TIM3_Init();
/* USER CODE BEGIN 2 */
HAL_TIM_PWM_Start(&htim3,TIM_CHANNEL_1);
/* 创建线程 */
rt_thread_t beep_control_task = rt_thread_create("beep_control",/* 线程名称 */
beep_control, RT_NULL,
1024, 3, 10); //
if(beep_control_task != RT_NULL)
{
/* 启动线程 */
rt_thread_startup(beep_control_task);
rt_kprintf("beep_control_task is already started\n");
}
else
{
rt_kprintf("beep_control_task thread is not started\n");
}
rt_thread_t led_control_task = rt_thread_create("led_control",/* 线程名称 */
led_control, RT_NULL,
1024, 3, 10); //
if(led_control_task != RT_NULL)
{
/* 启动线程 */
rt_thread_startup(led_control_task);
rt_kprintf("led_control_task is already started\n");
}
else
{
rt_kprintf("led_control_task thread is not started\n");
}
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
printf("getting...\n");
while (1)
{
SR04_GetData();
rt_thread_mdelay(1000);
/* 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_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 */
void beep_control(void* promt){
while (1)
{
int distant_int = distant;
HAL_GPIO_WritePin(beep_GPIO_Port,beep_Pin,GPIO_PIN_RESET);
rt_thread_mdelay(distant_int * 100);
HAL_GPIO_WritePin(beep_GPIO_Port,beep_Pin,GPIO_PIN_SET);
rt_thread_mdelay(distant_int * 100);
}
}
void led_control(void *promt)
{
while (1)
{
float pwm_state = (20.0-distant)/20.0;
int distant_int = distant;
int distant_pwm = (int)(pwm_state*500);
__HAL_TIM_SetCompare(&htim3, TIM_CHANNEL_1,distant_pwm);
rt_thread_mdelay(1000);
}
}
/* 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 */
3.实验效果
三. Modbus协议介绍
1. Modbus协议简介
Modbus 是一种应用层协议,主要用于工业自动化领域。它支持多种通信方式,包括RS232、RS485等。Modbus 协议定义了设备之间的通信方式,包括数据格式、错误检测和设备地址等。它允许设备通过Modbus协议进行读写操作,实现数据的交换。
2.RS485与RS232(UART)的不同:
- RS485 是一种差分信号通信协议,具有更强的抗干扰能力,适合长距离通信。它支持多点通信,即一个总线上可以连接多个设备,并且能够通过地址区分不同的设备。
- RS232(也称为UART)是一种单端信号通信协议,通常用于短距离通信,不支持多点通信。它通常用于点对点的通信方式。
3. 设计方案:
- 硬件设计:
- 使用 STM32F103 微控制器作为主控单元,因为它具有足够的处理能力和丰富的外设接口。
- 每个 HC-SR04 超声波模块连接到一个GPIO引脚,用于触发和接收超声波的回波信号。
- 使用RS485通信接口芯片,如 MAX485 或 SP485,连接到微控制器的相应引脚,实现数据的串行通信。
- 软件设计:
- 在STM32F103上编写固件,实现对HC-SR04模块的控制,包括触发超声波发射和读取回波时间。
- 实现Modbus协议栈,处理Modbus RTU(二进制模式)或Modbus TCP(网络模式)的数据包。
- 设计设备地址和功能码,以便在Modbus网络上识别和控制各个超声波雷达。
- 实现错误检测和处理机制,确保数据的准确性和通信的可靠性。
- 通信协议:
- 设计通信协议,定义如何通过RS485发送和接收数据,包括数据帧的格式、起始位、数据位、校验位和停止位。
- 确保Modbus协议的实现能够处理不同类型的功能码,如读取保持寄存器、写入保持寄存器等。
- 系统整合:
- 将硬件和软件整合,进行系统级的测试,确保超声波雷达能够准确测量距离,并通过Modbus协议正确地与外部系统通信。