Arduino Timer Delay example

tdelay_ms.c

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

#define F_CPU 16000000UL

static volatile uint32_t duration = 0x00;


ISR(TIMER0_COMPA_vect) {
	if (!duration) {
		TIMSK0 &= _BV(OCIE0A);
		TCCR0B = 0x00;
	}
	else {
		duration--;
	}
}


void tdelay_ms(uint16_t a_delay) {

	sei();
	power_timer0_enable();

	TCCR0A = 0x02;

	// prescaler = 64
	TCCR0B = 0x03;

	// divide frequency further on, by 125
	OCR0A = 0x7c;
	TCNT0 = 0x00;

	duration = a_delay;

	// enable interrupt
	TIMSK0 |= _BV(OCIE0A);

	while (duration);
}


int main(void)
{
	DDRB = 0xff;
	PORTB = 0x00;

	while (1) {
		PORTB ^= 0xff;
		tdelay_ms(1000);
	}
	
	return 0;
}