关于HC-SR04超声波测距模块（Trig和Echo的引脚可以自定义，我用的TRIG是PBout(11) ECHO是PBin(10)）
硬件连接：
Vcc ：5V输入（最好不要用3.3V输入）
Trig ：触发信号输入（直接给Trig高电平，然后读取Echo引脚是否为高电平，若为高电平，则开启定时器，然后继续检测等待其为低电平的时候，获取计数器值，然后进行计算）
Echo ：回响信号输出（开启外部中断，先将Echo配置上升沿中断，当中断来临的时候，在中断函数里面开启定时器，再将其配置为下降沿中断，等待下降沿中断来临的时候，获取计数器值）
Gnd：连接地线
在使用HC-SR04超声波测距模块时，前5次测量求取平均值，减少测量的误差
#include "hcsr04.h"
#include "SysTick.h"
#include "usart.h" u16 msHcCount = 0;void hcsr04_NVIC()//定时器4设置
{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);
}void Hcsr04Init()//IO口初始化 及其他初始化
{ 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); //1us进入一次更新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);
}static void OpenTimerForHc() //打开定时器4
{TIM_SetCounter(TIM4,0);msHcCount = 0;TIM_Cmd(TIM4, ENABLE);
}static void CloseTimerForHc() //关闭定时器4
{TIM_Cmd(TIM4, DISABLE);
}void TIM4_IRQHandler(void)//定时器4中断
{if (TIM_GetITStatus(TIM4, TIM_IT_Update) != RESET) {TIM_ClearITPendingBit(TIM4, TIM_IT_Update ); msHcCount++;}
}u32 GetEchoTimer(void)//获取定时器4计数器值
{u32 t = 0;t = msHcCount*1000;t += TIM_GetCounter(TIM4);TIM4->CNT = 0; delay_ms(50);return t;
}float Hcsr04GetLength(void)//通过定时器4计数器值推算距离
{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);//cmsum = lengthTemp + sum ;}lengthTemp = sum/5.0;return lengthTemp;
}#ifndef __HCSR04_H
#define __HCSR04_H #include "stm32f10x.h"
#include "sys.h"//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#define TRIG_Send PBout(11)
#define ECHO_Reci PBin(10)void hcsr04_NVIC(void);//定时器4设置
void Hcsr04Init(void);//IO口初始化 及其他初始化
static void OpenTimerForHc(void);//打开定时器4
static void CloseTimerForHc(void);//关闭定时器4
void TIM4_IRQHandler(void);//定时器4终中断
u32 GetEchoTimer(void);//获取定时器4计数器值
float Hcsr04GetLength(void);//通过定时器4计数器值推算距离#endif
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