/* 	Example to blink 8 leds like Knight-Rider connectet to a 
	PCF8574(A) i2c port expander.
*/

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/i2c.h>


#define PCF8574 0x20	/* PCF 8574, A0,A1,A2 = low		*/
#define wait 5		/* 100ms per led			*/

int i2c;								
char buf[1];

int mysleep( unsigned int s)  	/* my own sleep		  	*/
{				/* usleep waits only 20ms 	*/
  unsigned int i;		/* and ignore the parameter	*/
  for (i=0;i<s;i++) {		/* but the parameter must exist!*/
    usleep(1);						
  }
}

int main(void) 
{
	while (1) {				/* endless loop, kill the prozess with ^C */ 
	int count;
        i2c = open("/dev/i2c/0",O_RDWR);	/* open the device on first i2c-bus 	*/
        if ( i2c > 0 ) {
          ioctl(i2c,I2C_SLAVE, PCF8574); 	/* set the i2c chip address 		*/
          for (count=0;count<8;count++) {
              buf[0] = ~(1 << count);		/* shift first bit forward and  	*/
                                                /* invert all for low activ outputs	*/
              write(i2c,buf,1);			/* write 1 byte to the deivce 		*/ 
              mysleep(wait);
          }
          for (count=0;count<8;count++) {
              buf[0] = ~(0x80 >> count);	/* shift back			*/
              write(i2c,buf,1);
              mysleep(wait);
	  }
       	}
       	i2c = close(i2c);
    }
    return 0;
}