Balancing LED brightness for Binary Burst Clock

led-balance.c

#include <avr/io.h>
#include <avr/interrupt.h>

#define F_CPU 1000000

void init_IO(void) {
	DDRD |= (1<<PD0) | (1<<PD1) | (1<<PD2);
	PORTD |= (1<<PD0) | (1<<PD1) | (1<<PD2);
}

void init_Timers(void) {
	TIMSK0 |= (1<<TOIE0);	//enable overflow interrupt
	TCNT0 = (unsigned char)(signed short)-(((F_CPU / 64) * .0005) + 0.5);   //Prewind 500us
	sei();	//enable global interrupts
	TCCR0B |= (1<<CS01) | (1<<CS00);	//prescaler of 64
	
}


int main (void) {
	init_IO();
	init_Timers();
	while(1);
}

ISR(TIMER0_OVF_vect){
	PORTD = 0;
	static unsigned char state = 0x07;
	static unsigned char tracker = 0;
	PORTD = state;
	TCNT0 = (unsigned char)(signed short)-(((F_CPU / 64) * .0005) + 0.5);   //Prewind for next interrupt (500us)
	
	if (++tracker > 15) {
		tracker = 0;
		state = 0x07;
	}
	else if ((tracker > 1) && (tracker < 4)){
		state = 0x04;
	}
	else state = 0x00;