#include <inttypes.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/signal.h>
#include <stdlib.h>


#include <compat/deprecated.h>
#include <stdarg.h>
#include <ctype.h>
#include <string.h>

static volatile uint8_t led;
static volatile uint8_t direction;

SIGNAL(SIG_OVERFLOW0)		//signal handler for tcnt0 overflow interrupt
{
    PORTB = ~led;    

	if(direction==0)
	{
		led<<=1;		//move to next LED
	}
	else
	{
		led>>=1;
	}

	if(!led)		//overflow: start with PORT B0 again
	{
		if(direction)
		{
			direction = 0;
			led = 1;
		}
		else
		{
			direction = 1;
			led = 128;
		}
	
	}

	TCNT0= 0;		//reset counter to get this interrupt again
}

int main(void)
{
	DDRB = 0xff;	//use all pins on PORT B for output

	TIMSK = (1<<TOIE0);//enable TCNT0
	TCNT0 = 0;		//reset TCNT0
	TCCR0 = 5;		//count with cpu clock/1024

	led = 1;		//init variable representing the LED state
	direction = 0;

	sei();			//enable interrupts

	for(;;){}		//loop forever
}