test-led.c

父子进程实现

/*********************************************************************
* File：	test-led.c
* Author：	Embest
* Desc：		
* History：	
*			Original version, 2005.4 Embest
*			Program modify, 2005.06.05 Embest R.X.Huang <[e-mail]> 
*********************************************************************/

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


#define LED_NUM		4

#define LED_OFF		0
#define LED_ON		1
#define LED_ON_ALL	0xF
#define LED_OFF_ALL	0x0


int main(int argc, char** argv)
{
	int i, j, wval, rval, fd;
	static char *driver = "/dev/led/0";

	printf("LED test example base on Linux. \n");

	/* open led device */
	fd = open(driver, O_RDWR);
	if(fd <0)
	{
		printf("Can't not open %s\n",driver);
		return fd;
	}

	/* test single led */
	for(i=0; i<3; i++)
	{
		for(j=0; j<LED_NUM; j++)
		{
			wval = LED_ON<<j;
			write(fd, &wval, 1);
			read(fd, &rval, 1);
			printf("Turn on LED%d, readback val = 0x%02X\n", j+1, rval&0xF);
			/* delay 500ms */
			usleep(500*1000);
		}
	}
	
	/* test all leds */
	for(i=0; i<6; i++)
	{
		if(i%2)
		{
			wval = LED_OFF_ALL;
			write(fd, &wval, 1);
			read(fd, &rval, 1);
			printf("Turn off all LEDs, readback val = 0x%02X\n", rval&0xF);
		}
		else
		{
			wval = LED_ON_ALL;
			write(fd, &wval, 1);
			read(fd, &rval, 1);
			printf("Turn on all LEDs, readback val = 0x%02X\n", rval&0xF);
		}			
		/* delay 1s */
		sleep(1);
	}

	printf(" end.\n");
	/* close led device */
	close(fd);

	return 0;
}