基于STM32F103C8T6的超声波测距示例

一、所需材料：

1、面包板：

https://item.taobao.com/item.htm?spm=a1z10.3-c-s.w4002-17409464480.12.942e3961LSzalG&id=566952992749

2、STM32F103C8T6核心板

https://item.taobao.com/item.htm?spm=a1z10.3-c-s.w4002-17409464480.12.69693961YaTulR&id=567200541464

3、超声波模块

https://item.taobao.com/item.htm?spm=a1z10.3-c-s.w4002-17409464480.12.306c3961DPKmG1&id=567318723493

4、串口工具

https://item.taobao.com/item.htm?spm=a1z10.3-c-s.w4002-17409464480.21.7dd33961iRVAkv&id=567201073239

5、STlink 下载程序，或用串口下载亦可

二、超声波原理分析

网上一大堆，以后待补

备注：HC-SR04在距离3cm内无法准确测量，近处3CM外测量误差0.7cm左右。

三、硬件连接

实际效果图：

四、源码分析

#include "delay.h"
#include "sys.h"
#include "usart.h"  
/***************************************************
大海电子专营各种电子模块，欢迎光临
硬件连接
串口1：RX PA10  TX PA9
超声波：Trig PB11    ECHG PB10
备注：以下代码非原创，只是经过修改适配成C8T6
若侵权，请告知。


***************************************************/


//超声波硬件接口定义
#define HCSR04_PORT     GPIOB
#define HCSR04_CLK      RCC_APB2Periph_GPIOB
#define HCSR04_TRIG     GPIO_Pin_11
#define HCSR04_ECHO     GPIO_Pin_10


 


//超声波计数
u16 msHcCount = 0;


//定时器4设置
void hcsr04_NVIC()
{
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);

NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;             
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;  
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;         
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;       
NVIC_Init(&NVIC_InitStructure);
}


//IO口初始化 及其他初始化
void Hcsr04Init()
{  
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;   
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_APB2PeriphClockCmd(HCSR04_CLK, ENABLE);
   
    GPIO_InitStructure.GPIO_Pin =HCSR04_TRIG;      
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(HCSR04_PORT, &GPIO_InitStructure);
    GPIO_ResetBits(HCSR04_PORT,HCSR04_TRIG);
     
    GPIO_InitStructure.GPIO_Pin =   HCSR04_ECHO;     
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(HCSR04_PORT, &GPIO_InitStructure);  
    GPIO_ResetBits(HCSR04_PORT,HCSR04_ECHO);    
     
          
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);   
     
    TIM_DeInit(TIM2);
    TIM_TimeBaseStructure.TIM_Period = (1000-1); 
    TIM_TimeBaseStructure.TIM_Prescaler =(72-1); 
    TIM_TimeBaseStructure.TIM_ClockDivision=TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
    TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);          
        
    TIM_ClearFlag(TIM4, TIM_FLAG_Update);  
    TIM_ITConfig(TIM4,TIM_IT_Update,ENABLE);    
    hcsr04_NVIC();
    TIM_Cmd(TIM4,DISABLE);     
}




//打开定时器4
static void OpenTimerForHc()  
{
   TIM_SetCounter(TIM4,0);
   msHcCount = 0;
   TIM_Cmd(TIM4, ENABLE); 
}


//关闭定时器4
static void CloseTimerForHc()    
{
   TIM_Cmd(TIM4, DISABLE); 
}


//定时器4终中断
void TIM4_IRQHandler(void)  
{
   if (TIM_GetITStatus(TIM4, TIM_IT_Update) != RESET)  
   {
       TIM_ClearITPendingBit(TIM4, TIM_IT_Update  ); 
       msHcCount++;
   }
}
 


//获取定时器4计数器值
u32 GetEchoTimer(void)
{
   u32 t = 0;
   t = msHcCount*1000;
   t += TIM_GetCounter(TIM4);
   TIM4->CNT = 0;  
   delay_ms(50);
   return t;
}
 
//通过定时器4计数器值推算距离
float Hcsr04GetLength(void )
{
   u32 t = 0;
   int i = 0;
   float lengthTemp = 0;
   float sum = 0;
   while(i!=5)
   {
      TRIG_Send = 1;      
      delay_us(20);
      TRIG_Send = 0;
      while(ECHO_Reci == 0);      
      OpenTimerForHc();        
      i = i + 1;
      while(ECHO_Reci == 1);
      CloseTimerForHc();        
      t = GetEchoTimer();        
      lengthTemp = ((float)t/58.0);//cm
      sum = lengthTemp + sum ;
        
    }
    lengthTemp = sum/5.0;
    return lengthTemp;
}
 
//测试主函数
int main(void)
 {  
float length;
delay_init();     //延时函数初始化  
NVIC_Configuration(); //设置NVIC中断分组2:2位抢占优先级，2位响应优先级
uart_init(9600); //串口初始化为9600
Hcsr04Init();
printf("大海电子串口测试rn");  
    
   Hcsr04Init();    
   printf("超声波初始化成功!n");

   while(1) 
{  
     length = Hcsr04GetLength();
     printf("距离为:%.3fcmn",length);
delay_ms(1000);    
}
 }