树莓派简单的外设开发——继电器、超声波测距

继电器部分代码

继电器连接太简单了，一个VCC,一个GND,一个GPIO即可，就不具体赘述了，下面直接上代码:

#include <wiringPi.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define SWITCH_INT4 26 //GPIO.26
#define SWITCH_INT3 27 //GPIO.27
#define SWITCH_INT2 28 //GPIO.28
#define SWITCH_INT1 29 //GPIO.29

int main()
{
        char cmd[12] = {'\0'};
        if(wiringPiSetup()==-1){
			printf("init error\n");
			exit(-1);
		}

        pinMode(SWITCH_INT4,OUTPUT);
        pinMode(SWITCH_INT3,OUTPUT);
        pinMode(SWITCH_INT2,OUTPUT);
        pinMode(SWITCH_INT1,OUTPUT);
    
        digitalWrite(SWITCH_INT1,HIGH);
        digitalWrite(SWITCH_INT2,HIGH);
        digitalWrite(SWITCH_INT3,HIGH);
        digitalWrite(SWITCH_INT4,HIGH);
    
        while(1){
        printf("please input: number on/off\n");

        gets(cmd);

        if(strcmp(cmd,"26 on")==0){
                digitalWrite(SWITCH_INT4,LOW);
        }else if(strcmp(cmd,"26 off")==0){
                digitalWrite(SWITCH_INT4,HIGH);
        }    
        if(strcmp(cmd,"27 on")==0){
                digitalWrite(SWITCH_INT3,LOW);
        }else if(strcmp(cmd,"27 off")==0){
                digitalWrite(SWITCH_INT3,HIGH);
        }
        if(strcmp(cmd,"28 on")==0){
                digitalWrite(SWITCH_INT2,LOW);
        }else if(strcmp(cmd,"28 off")==0){
                digitalWrite(SWITCH_INT2,HIGH);
        }

        if(strcmp(cmd,"29 on")==0){
                digitalWrite(SWITCH_INT1,LOW);
        }else if(strcmp(cmd,"29 off")==0){
                digitalWrite(SWITCH_INT1,HIGH);
        }
        if(strcmp(cmd,"all on")==0){
                digitalWrite(SWITCH_INT1,LOW);
                digitalWrite(SWITCH_INT2,LOW);
                digitalWrite(SWITCH_INT3,LOW);
                digitalWrite(SWITCH_INT4,LOW);
        }else if(strcmp(cmd,"all off")==0){
                digitalWrite(SWITCH_INT1,HIGH);
                digitalWrite(SWITCH_INT2,HIGH);
                digitalWrite(SWITCH_INT3,HIGH);
                digitalWrite(SWITCH_INT4,HIGH);
        }else{
                printf("the error strlen\n");
             }
        }
        return 0;
}

超声波测距模块（HC-SR40）

#include <wiringPi.h>
#include <stdio.h>
#include <sys/time.h>
#define Trig    4//GPIO.4
#define Echo    5//GPIO.5

void ultraInit(void)
{
    pinMode(Echo, INPUT);  //设置端口为输入，echo检测信号
    pinMode(Trig, OUTPUT);  //设置端口Trig为输出，给Trig触发信号
}

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
    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;
}