avrinput/time.c

#include "time.h"
#include "conf.h"

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

volatile struct eigentime_s _eigentime_ms;

void
time_init(void)
{
	_eigentime_ms.low = 0;
	_eigentime_ms.high = 0;
	_eigentime_ms.tenth = 0;
	// prescaler is 64.
	TCCR0B = _BV(CS00) | _BV(CS01);
	TIMSK0 |= _BV(TOIE0);
	sei();
}


void
get_eigentime(struct eigentime_s * time)
{
	time->low = _eigentime_ms.low;
	time->high = _eigentime_ms.high;
}

ISR(TIMER0_OVF_vect)
{
	unsigned int last_eigentime_low = _eigentime_ms.low;
	unsigned int ms;

	// well basically at 20Mhz milliseconds are not precise enough.
	_eigentime_ms.tenth += TIME_TENTH_MILLIS_PER_OVERFLOW;
	if(_eigentime_ms.tenth > 10)
	{
		ms = _eigentime_ms.tenth / 10;
		_eigentime_ms.low += ms;
		_eigentime_ms.tenth -= 10 * ms;
	}


	// Handle the overflow.
	if(_eigentime_ms.low < last_eigentime_low)
	{
		_eigentime_ms.high++;
	}
}