led_test.c

uclinux字符设备驱动编写的基本原理和过程,帮助刚刚入门的朋友一点提示

#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<linux/fcntl.h>

#define LED_NUM 4

int main(int argc,char **argv)
{
	int i,j,wval,rval,fd;
	printf("Test LED...\n");
	/*open led device*/
	fd=open("/dev/led0",0_RDWR);
	
	/*test single led*/
	for(i=0;i<3;i++){
		for(j=0;j<LED_NUM;j++){
			wval=1<<j;
			write(fd,&wval,1);
			read(fd,&rval,1);
			printf("Turn on LED %d,readback val=0x%02X\n",j+1,rval);
			usleep(500*1000);//500ms
		}
	}
	
	/*test all leds*/
	for(i=0;i<6;i++){
		if(i%2){
			wval=0x00;
			write(fd,&wval,1);
			read(fd,&rval,1);
			printf("Turn off all LEDs,readback val=0x%02X\n",rval);
		}
		else{
			wval=0x0f;
			write(fd,&wval,1);
			read(fd,&rval,1);
			printf("Turn on all LEDs,readback val=0x%02X\n",rval);
		}
		sleep(1);
	}

	close(fd);
	return 0;
}