butt_test.c

led control 在s3c2410 同时还有key board

#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <sys/ioctl.h> 
#include <sys/types.h> 
#include <sys/stat.h> 
#include <fcntl.h> 
#include <sys/select.h> 
#include <sys/time.h> 
#include <errno.h> 
 
int main(void) 
{ 
 int buttons_fd; 
 int key_value; 
 buttons_fd = open("/dev/buttons", 0); 
 if (buttons_fd < 0) { 
   perror("open device buttons"); 
   exit(1); 
 } 
 
 for (;;) { 
   fd_set rds; 
   int ret; 
 
   FD_ZERO(&rds); 
   FD_SET(buttons_fd, &rds); 
 
   /*使用系统调用select检查是否能够从/dev/buttons设备读取数据*/ 
   ret = select(buttons_fd + 1, &rds, NULL, NULL, NULL); 
    
   /*读取出错则退出程序*/ 
if (ret < 0) { 
   perror("select"); 
   exit(1); 
   } 
    
   if (ret == 0) { 
   printf("Timeout.\n"); 
   }  
   /*能够读取到数据*/ 
else if (FD_ISSET(buttons_fd, &rds)) { 
 /*开始读取键盘驱动发出的数据，注意key_value和键盘驱动中定义为一致的类型
*/ 
     int ret = read(buttons_fd, &key_value, sizeof key_value); 
     if (ret != sizeof key_value) { 
    if (errno != EAGAIN) 
     perror("read buttons\n"); 
    continue; 
   } else { 
    /*打印键值*/ 
    printf("buttons_value: %d\n", key_value); 

   } 

     
   } 
 } 
 
 /*关闭设备文件句柄*/ 
 close(buttons_fd); 
 return 0; 
}