超声波传感器 原理 及其功能

超声波测距步骤

HC_SR04.c

#include "stm32f10x.h"                  // Device header
#include "SysTick.h"
#include "HC_SR04.h"


extern uint16_t mscount = 0;   //extern 让main函数也能使用这里这个

void HC_SR04(void)
{
		GPIO_InitTypeDef GPIO_HC_SR04init;//1.配置GPIO引脚结构体 Trig PB11 Echo PB10
		TIM_TimeBaseInitTypeDef TIM_HC_SR04init;//2.配置定时器结构体
	  NVIC_InitTypeDef NVIC_HC_SR04init;//3.配置定时器中断结构体
	
		NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
	
	  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);//4.开启时钟（定时器，GPIO）
		RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

		//Trig PB11
		GPIO_HC_SR04init.GPIO_Mode  = GPIO_Mode_Out_PP; 
		GPIO_HC_SR04init.GPIO_Pin   =	GPIO_Pin_11;	
		GPIO_HC_SR04init.GPIO_Speed = GPIO_Speed_50MHz;
	  GPIO_Init( GPIOB, &GPIO_HC_SR04init );
	
		//Echo PB10
		GPIO_HC_SR04init.GPIO_Mode = GPIO_Mode_IN_FLOATING;
		GPIO_HC_SR04init.GPIO_Pin  = GPIO_Pin_10;
		GPIO_Init( GPIOB, &GPIO_HC_SR04init );
	
		TIM_HC_SR04init.TIM_ClockDivision  = TIM_CKD_DIV1;
		TIM_HC_SR04init.TIM_CounterMode    = TIM_CounterMode_Up;
		TIM_HC_SR04init.TIM_Period         = 100 - 1 ; //1ms
		TIM_HC_SR04init.TIM_Prescaler      = 72 - 1 ;  //72M
		TIM_TimeBaseInit( TIM4, &TIM_HC_SR04init);
	  TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE);
		TIM_Cmd( TIM4, DISABLE );  //先关闭
	
		NVIC_HC_SR04init.NVIC_IRQChannel = TIM4_IRQn;
		NVIC_HC_SR04init.NVIC_IRQChannelPreemptionPriority = 0;
		NVIC_HC_SR04init.NVIC_IRQChannelSubPriority = 0;
		NVIC_HC_SR04init.NVIC_IRQChannelCmd = ENABLE;
		NVIC_Init(&NVIC_HC_SR04init);

	
}
//打开定时器4
void Open_tim4(void)	
{
		TIM_SetCounter( TIM4,  0);
		mscount = 0;
		TIM_Cmd( TIM4, ENABLE );  

	
}
//关闭定时器4
void Close_tim4(void)
{
				TIM_Cmd( TIM4, DISABLE );  //关闭


}
//定时器中断服务函数
void TIM4_IRQHandler(void)
{
	 if ( TIM_GetITStatus(TIM4,  TIM_IT_Update) != RESET)     //判断是否发生中断
	 {
				TIM_ClearITPendingBit(TIM4, TIM_IT_Update);   //清楚标记位
				mscount++; //记录发生的中断次数

	 
	 }


}
//获取定时器计数器的值
int GetEcho_time(void)
{
		uint32_t t = 0;
		t = mscount * 1000;   //发生了多少个中断 *1000 
		t += TIM_GetCounter(TIM4);
		TIM4->CNT = 0;
		ms_delay(50);
	
		return t;

}
//获取超声波测距距离
float GetLength(void)
{
	int i = 0;
	uint16_t t = 0;
	float length = 0;
	float sum = 0;
	
	while(i != 5)
	{
		TRIG_Send(1);
		us_delay(20);
		TRIG_Send(0);
		
		while(ECHO_Reci == 0);
				Open_tim4();
				i=i+1;
		while(ECHO_Reci == 1);
				t = GetEcho_time();
				length =((float) t / 58.0);
				sum = sum +length;
		
	}
		length = sum / 5.0;
		return length;

}

HC_SR04.h

#ifndef _HC_SR04_H
#define _HC_SR04_H

#include "stm32f10x.h"                  // Device header
void HC_SR04(void);

void Open_tim4(void);
void Close_tim4(void);
int GetEcho_time(void);
float GetLength(void);

#define ECHO_Reci    	GPIO_ReadInputDataBit( GPIOB, GPIO_Pin_10)
 
#define TRIG_Send(a)  if(a) \
											GPIO_SetBits(GPIOB, GPIO_Pin_11); \
											else \
											GPIO_ResetBits(GPIOB, GPIO_Pin_11)

#endif
											

main.c

#include "stm32f10x.h"                  // Device header
#include "usart.h"
#include "led.h"
#include "tim.h"
#include "motor.h"
#include "SysTick.h"
#include "HC_SR04.h"



void delay(uint16_t time)
{
		uint16_t i = 0;
		while(time--)
		{
			i=12000;
			while(i--);
		}
}

int main(void)
{
		float Length = 0;
		HC_SR04();
		Usart_Init();

	while(1)
	{
				Length = GetLength();
				printf("%.3f\r\n",Length);
				ms_delay(500);
	}
	
}