#define F_CPU 8000000UL
#define UART_BAUD 9600

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

static volatile unsigned char ticks = 0;

ISR(TIMER0_OVF0_vect) {
    ticks++;
}

int main(void) {
    uart_init();
    uart_putchar('i');
    TCCR0 = _BV(CS02); /* CLK/256 */
    TIMSK = _BV(TOIE0); /* OVF */
    uart_putchar('I');
    sei();
    
    for (;;) {
	/* (8*10^6 Hz)/256/256/122 = 1 Hz */
	if (ticks >= 122) {
	    ticks = 0;
	    uart_putchar('O');
	}
    }
}