1.驱动代码
树莓派驱动超声波模块驱动代码如下:
#include <wiringPi.h>
#include <stdio.h>
#include <sys/time.h>
#define Trig 4
#define Echo 5
void ultraInit(void)
{
pinMode(Echo, INPUT); //设置端口为输入
pinMode(Trig, OUTPUT); //设置端口为输出
}
float disMeasure(void)
{
struct timeval tv1; //timeval是time.h中的预定义结构体 其中包含两个一个是秒,一个是微秒
/*
struct timeval
{
time_t tv_sec; //Seconds.
suseconds_t tv_usec; //Microseconds.
};
*/
struct timeval tv2;
long start, stop;
float dis;
digitalWrite(Trig, LOW);
delayMicroseconds(2);
digitalWrite(Trig, HIGH);
delayMicroseconds(10); //发出超声波脉冲
digitalWrite(Trig, LOW);
while(!(digitalRead(Echo) == 1));
gettimeofday(&tv1, NULL); //获取当前时间 开始接收到返回信号的时候
while(!(digitalRead(Echo) == 0));
gettimeofday(&tv2, NULL); //获取当前时间 最后接收到返回信号的时候
/*
int gettimeofday(struct timeval *tv, struct timezone *tz);
The functions gettimeofday() and settimeofday() can get and set the time as well as a timezone.
The use of the timezone structure is obsolete; the tz argument should normally be specified as NULL.
*/
start = tv1.tv_sec * 1000000 + tv1.tv_usec; //微秒级的时间
stop = tv2.tv_sec * 1000000 + tv2.tv_usec;
dis = (float)(stop - start) / 1000000 * 34000 / 2; //计算时间差求出距离
return dis;
}
int main(void)
{
float dis;
if(wiringPiSetup() == -1){
//如果初始化失败,就输出错误信息 程序初始化时务必进行
printf("setup wiringPi failed !");
return 1;
}
ultraInit();
while(1){
dis = disMeasure();
printf("distance = %0.2f cm\n",dis);
delay(1000);
}
return 0;
}
2 注意
超声波模块的VCC电源要接5V的,如果接3.3V,模块的测距数值会不正确,在同一个数值范围波动。