timers.c

WWVB receiver using AVR.

/* $Id: timers.c,v 1.5 2005/10/30 19:44:38 simimeie Exp $
 * Functions that work with the avrs timer(s).
 * Mainly a function that allows you to get sort of a timestamp.
 */ 

#define BV _BV
#include <avr/io.h>
#include <avr/signal.h>
#include "timers.h"
 
static volatile uint16_t ticks;
static volatile uint16_t seconds;
static volatile uint8_t isvalid;

/* This interrupt handler gets called when counter 0 overflows */
SIGNAL(SIG_OVERFLOW0) {
	ticks++;
	if (ticks >= TICKSPERSECOND) {
		ticks = 0;
		seconds++;
	}
	isvalid++;
}

#ifdef HIGHRESTIMER
/* This interrupt handler gets called when counter 1 overflows.
 * This should never happen, but we need to signal THAT it happened.
 * So we stop the timer and set it to 0. */
SIGNAL(SIG_OVERFLOW1) {
	TCCR1B = 0;
	TCNT1H = 0; /* High has to be WRITTEN first */
	TCNT1L = 0;
}

void starthighrestimer(void) {
	TCNT1H = 0; /* High has to be WRITTEN first */
	TCNT1L = 0;
	TCCR1B = 0x05; /* CLK/1024 */
}

uint16_t readhighrestimer(void) {
	TCCR1B = 0; /* Stop it */
	/* Split into two lines to force execution sequence */
	uint8_t tmp = TCNT1L; /* Low has to be READ first */
	return ((((uint16_t)(TCNT1H)) << 8) | tmp);
}
#endif

void timers_init(void) {
	TIMSK |= BV(TOIE0);
#ifdef HIGHRESTIMER
	TIMSK |= BV(TOIE1);
#endif
	TCCR0 = 0x03; /* CLK/64 */
}

void timers_zero(void) {
	if (ticks > (TICKSPERSECOND / 2)) {
		seconds++;
	}
	ticks = 0;
}

void gettickdata(struct tickdata * td) {
	uint8_t lastiv;
	do {
		lastiv = isvalid;
		td->seconds = seconds;
		td->ticks = ticks;
	} while (lastiv != isvalid); /* In that case we got interrupted */
	return;
}

uint16_t getseconds(void) {
	uint8_t lastiv;
	uint16_t res;
	do {
		lastiv = isvalid;
		res = seconds;
	} while (lastiv != isvalid); /* In that case we got interrupted */
	return res;
}