【触觉智能 Purple Pi开发板试用】C流水灯

linux环境下面，对gpio的控制，点灯是基本功之一，今天偿试用C语言进行点灯。

对gpio的操作是基于文件/sys/class/gpio下面的读写操作：

1、是对/sys/class/gpio/export写入需要操作的IO编号，来启用IO，这次选用89、88、87行操作。

2、对/sys/class/gpio/gpio89/direction写入out来定义IO为输出。

3、在上面两个步骤完成后，对/sys/class/gpio/gpio89/value进行写入1或者0来确定输出高低电平。

4、对IO控制结束后，对`/sys/class/gpio/unexport进入关闭，要不然再次对IO进行操作时，会显示IO busy的错误信息。

书写led_example.c内容如下：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

int main(int argc ,char *argv[])
{
    FILE *fp=NULL;
    int i=0;
    fp = fopen("/sys/class/gpio/export","w");
    fprintf(fp,"%d",89);
    fclose(fp);
    fp = fopen("/sys/class/gpio/export","w");
    fprintf(fp,"%d",88);
    fclose(fp);
    fp = fopen("/sys/class/gpio/export","w");
    fprintf(fp,"%d",87);
    fclose(fp);
    fp = fopen("/sys/class/gpio/gpio89/direction","w");
    fprintf(fp,"out");
    fclose(fp);
    fp = fopen("/sys/class/gpio/gpio88/direction","w");
    fprintf(fp,"out");
    fclose(fp);
    fp = fopen("/sys/class/gpio/gpio87/direction","w");
    fprintf(fp,"out");
    fclose(fp);
    for(i=0;i<100;i++)
    {
        fp = fopen("/sys/class/gpio/gpio89/value","w");
        fprintf(fp,"%d",1);
        fclose(fp);
        fp = fopen("/sys/class/gpio/gpio88/value","w");
        fprintf(fp,"%d",0);
        fclose(fp);
        fp = fopen("/sys/class/gpio/gpio87/value","w");
        fprintf(fp,"%d",0);

        fclose(fp);
        sleep(1);
        fp = fopen("/sys/class/gpio/gpio89/value","w");
        fprintf(fp,"%d",0);

        fclose(fp);
        fp = fopen("/sys/class/gpio/gpio88/value","w");
        fprintf(fp,"%d",1);

        fclose(fp);
        fp = fopen("/sys/class/gpio/gpio87/value","w");
        fprintf(fp,"%d",0);
        sleep(1);
        fclose(fp);
        fp = fopen("/sys/class/gpio/gpio89/value","w");
        fprintf(fp,"%d",0);

        fclose(fp);
        fp = fopen("/sys/class/gpio/gpio88/value","w");
        fprintf(fp,"%d",0);

        fclose(fp);
        fp = fopen("/sys/class/gpio/gpio87/value","w");
        fprintf(fp,"%d",1);
        fclose(fp);
        sleep(1);

    }
    fp = fopen("/sys/class/gpio/unexport","w");
    fprintf(fp, "%d",89);
    fclose(fp);
    fp = fopen("/sys/class/gpio/unexport","w");
    fprintf(fp, "%d",88);
    fclose(fp);
    fp = fopen("/sys/class/gpio/unexport","w");
    fprintf(fp, "%d",87);
    fclose(fp);
    return 0;

}

编译，上传到开发板：

parallels@parallels-Parallels-Virtual-Platform:~/Documents/helloworld$ arm-linux-gnueabihf-gcc led_expamle.c -o led_expamle
parallels@parallels-Parallels-Virtual-Platform:~/Documents/helloworld$ scp led_expamle root@192.168.3.169:/root/
root@192.168.3.169's password: 
led_expamle                                                           100%   12KB   1.9MB/s   00:00    
parallels@parallels-Parallels-Virtual-Platform:~/Documents/helloworld$

然后执行./led_example，可以看到LED灯依次点亮：