pentabug/firmware/lib/util.c

#include <stdint.h>
#include <avr/interrupt.h>
#include <avr/common.h>
#include <avr/io.h>
#include "util.h"

static volatile uint8_t internal_counter;

void timer_init(void) {
	/* initialize timer2, CTC at 10ms, prescaler 1024 */
	OCR2A = F_CPU / 1024 / 100;
	TCCR2A = _BV(WGM21);
	TCCR2B = _BV(CS22) | _BV(CS21) | _BV(CS20);
	TIMSK2 = _BV(OCIE2A);
}

void timer_set(timer_t *t, uint8_t timeout) {
	t->current = internal_counter;
	t->timeout = timeout;
}

void timerL_set(timerL_t *t, uint16_t timeout) {
	t->current = internal_counter;
	t->timeout = timeout;
}

bool timer_expired(timer_t *t) {
	if (t->timeout == 0)
		return true;

	/* attention: may fail if internal counter is incremented by more than one
	 * between two calls of timer_expired()! (that is if its is called less than every 10ms*/
	if (t->current != internal_counter) {
		t->timeout--;
		t->current = internal_counter;
	}

	return false;
}

bool timerL_expired(timerL_t *t) {
	if (t->timeout == 0)
		return true;

	/* attention: may fail if internal counter is incremented by more than one
	 * between two calls of timer_expired()! */
	if (t->current != internal_counter) {
		t->timeout--;
		t->current = internal_counter;
	}

	return false;
}

/* timer interrupt function */ISR(TIMER2_COMPA_vect, ISR_NOBLOCK) {
	internal_counter++;
}