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/*
Copyright 2011 Jun Wako <wakojun@gmail.com>
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, see <http://www.gnu.org/licenses/>.
*/
#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdint.h>
#include "timer.h"
// counter resolution 1ms
volatile uint16_t timer_count = 0;
void timer_init(void)
{
// Timer0 CTC mode
TCCR0A = 0x02;
#if TIMER_PRESCALER == 1
TCCR0B = 0x01;
#elif TIMER_PRESCALER == 8
TCCR0B = 0x02;
#elif TIMER_PRESCALER == 64
TCCR0B = 0x03;
#elif TIMER_PRESCALER == 256
TCCR0B = 0x04;
#elif TIMER_PRESCALER == 1024
TCCR0B = 0x05;
#else
# error "Timer prescaler value is NOT vaild."
#endif
OCR0A = TIMER_RAW_TOP;
TIMSK0 = (1<<OCIE0A);
}
inline
void timer_clear(void)
{
uint8_t sreg = SREG;
cli();
timer_count = 0;
SREG = sreg;
}
inline
uint16_t timer_read(void)
{
uint16_t t;
uint8_t sreg = SREG;
cli();
t = timer_count;
SREG = sreg;
return t;
}
inline
uint16_t timer_elapsed(uint16_t last)
{
uint16_t t;
uint8_t sreg = SREG;
cli();
t = timer_count;
SREG = sreg;
return TIMER_DIFF_MS(t, last);
}
// excecuted once per 1ms.(excess for just timer count?)
ISR(TIMER0_COMPA_vect)
{
timer_count++;
}
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