git.zerfleddert.de Git - fnordlicht-mini/blob - firmware/fnordlicht-controller/timer.c

   1 /*
   2  * unzap firmware
   3  *
   4  * (c) by Alexander Neumann <alexander@lochraster.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  *
  19  * For more information on the GPL, please go to:
  20  * http://www.gnu.org/copyleft/gpl.html
  21  */
  22
  23 #include <stdint.h>
  24 #include <avr/interrupt.h>
  25 #include "../common/io.h"
  26 #include "timer.h"
  27
  28 static volatile uint8_t internal_counter;
  29
  30 void timer_init(void)
  31 {
  32 #if defined(__AVR_ATmega8__)
  33     /* initialize timer2, CTC at 10ms, prescaler 1024 */
  34     OCR2 = F_CPU/1024/100;
  35     TCCR2 = _BV(WGM21) | _BV(CS22) | _BV(CS21) | _BV(CS20);
  36     TIMSK |= _BV(OCIE2);
  37 #elif defined(__AVR_ATmega48__) || defined(__AVR_ATmega88__) || defined(__AVR_ATmega168__)
  38     /* initialize timer2, CTC at 10ms, prescaler 1024 */
  39     OCR2A = F_CPU/1024/100;
  40     TCCR2A = _BV(WGM21);
  41     TCCR2B = _BV(CS22) | _BV(CS21) | _BV(CS20);
  42     TIMSK2 = _BV(OCIE2A);
  43 #else
  44 #error "unknown controller, unable to initialize timer2"
  45 #endif
  46 }
  47
  48 void timer_set(timer_t *t, uint8_t timeout)
  49 {
  50     t->current = internal_counter;
  51     t->timeout = timeout;
  52 }
  53
  54 bool timer_expired(timer_t *t)
  55 {
  56     if (t->timeout == 0)
  57         return true;
  58
  59     /* attention: this is not correct, if internal_counter is incremented by more than one
  60      * between two calls of timer_expired()! */
  61     if (t->current != internal_counter) {
  62         t->timeout--;
  63         t->current = internal_counter;
  64     }
  65
  66     return false;
  67 }
  68
  69 /* timer interrupt function */
  70 #if defined(__AVR_ATmega8__)
  71 ISR(TIMER2_COMP_vect, ISR_NOBLOCK) {
  72     internal_counter++;
  73 }
  74 #elif defined(__AVR_ATmega48__) || defined(__AVR_ATmega88__) || defined(__AVR_ATmega168__)
  75 ISR(TIMER2_COMPA_vect, ISR_NOBLOCK) {
  76     internal_counter++;
  77 }
  78 #endif