am335x -- kio 控制接口

//example
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#define GPIO_TO_PIN(bank, gpio) (32 * (bank) + (gpio))

int main(int argc, char * argv)
{
        int i, n, fd;
        char num，val;
        int ret;
        fd = open("/dev/kio", O_RDWR);                //打开设备
        if (fd < 0)
        {
            printf("can't open /dev/kio! ");
            exit(1);
        }
        sleep(1);
        ioctl(fd, 1, GPIO_TO_PIN(1,22));                //设置gpio1-22为输出（user:led3）
        ioctl(fd, 0, GPIO_TO_PIN(2, 1));                //设置gpio2-1 为输入（p8-18）
        while (1)
        {
                num = 1;
                ret = write(fd,"1",GPIO_TO_PIN(1,22)); //置高
                if(ret < 0)
                {
                        perror("write");
                        return -1;
                }
                sleep(1);
                ret = write(fd,"0",GPIO_TO_PIN(1,22));//置低
                if(ret < 0)
                {
                    perror("write");
                    return -1;
　　　　 }

  　　　　ret = read(fd, &val, GPIO_TO_PIN(2,1)); //读取电平

             if(ret == 1) //高电平

                 printf("val==1 ");

             if(ret == 0)　// 低电平

                 printf("val == 0 ");

　　}

}