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/*
* Timer routines
*
* Copyright (c) 2015-2016 Michael Buesch <m@bues.ch>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "timer.h"
#include <avr/io.h>
static _timcnt_t _timer_count_now;
ISR(TIMER0_COMPA_vect)
{
_timer_count_now++;
mb();
}
_timcnt_t timer_now(void)
{
_timcnt_t count;
uint8_t sreg;
sreg = irq_disable_save();
count = _timer_count_now;
irq_restore(sreg);
return count;
}
static _signed_timcnt_t _timer_ms_to_count(int32_t millisec)
{
return (_signed_timcnt_t)sdiv_round_up((int32_t)TIMERCPS * millisec,
(int32_t)1000);
}
static int32_t _timer_count_to_ms(_signed_timcnt_t count)
{
return sdiv_round((int32_t)count * (int32_t)1000,
(int32_t)TIMERCPS);
}
static _signed_timcnt_t _timer_count_since(const struct timer *timer)
{
return (_signed_timcnt_t)(timer_now() - timer->count);
}
bool timer_expired(const struct timer *timer)
{
return _timer_count_since(timer) >= 0;
}
int32_t timer_ms_since(const struct timer *timer)
{
return _timer_count_to_ms(_timer_count_since(timer));
}
void timer_arm(struct timer *timer, int32_t millisec)
{
timer->count = (_timcnt_t)(timer_now() +
(_timcnt_t)_timer_ms_to_count(millisec));
}
void timer_set_now(struct timer *timer)
{
timer->count = timer_now();
}
void timer_add(struct timer *timer, int32_t millisec)
{
timer->count = (_timcnt_t)(timer->count +
(_timcnt_t)_timer_ms_to_count(millisec));
}
void timer_init(void)
{
build_assert(F_CPU == 8000000ul);
/* Initialize timer-0 as system timer. */
OCR0A = 125;
TCNT0 = 0;
/* CTC mode; PS 64 */
TCCR0A = (1 << WGM01) | (0 << WGM00);
TCCR0B = (0 << WGM02) | (0 << CS02) | (1 << CS01) | (1 << CS00);
/* Enable OC interrupt. */
TIFR0 = (1 << OCF0A);
TIMSK0 |= (1 << OCIE0A);
}
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