common/avr/timer.c

   1 /*
   2 Copyright 2011 Jun Wako <wakojun@gmail.com>
   3
   4 This program is free software: you can redistribute it and/or modify
   5 it under the terms of the GNU General Public License as published by
   6 the Free Software Foundation, either version 2 of the License, or
   7 (at your option) any later version.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 GNU General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16 */
  17
  18 #include <avr/io.h>
  19 #include <avr/interrupt.h>
  20 #include <stdint.h>
  21 #include "timer_avr.h"
  22 #include "timer.h"
  23
  24
  25 // counter resolution 1ms
  26 // NOTE: union { uint32_t timer32; struct { uint16_t dummy; uint16_t timer16; }}
  27 volatile uint32_t timer_count = 0;
  28
  29 void timer_init(void)
  30 {
  31     // Timer0 CTC mode
  32     TCCR0A = 0x02;
  33
  34 #if TIMER_PRESCALER == 1
  35     TCCR0B = 0x01;
  36 #elif TIMER_PRESCALER == 8
  37     TCCR0B = 0x02;
  38 #elif TIMER_PRESCALER == 64
  39     TCCR0B = 0x03;
  40 #elif TIMER_PRESCALER == 256
  41     TCCR0B = 0x04;
  42 #elif TIMER_PRESCALER == 1024
  43     TCCR0B = 0x05;
  44 #else
  45 #   error "Timer prescaler value is NOT vaild."
  46 #endif
  47
  48     OCR0A = TIMER_RAW_TOP;
  49     TIMSK0 = (1<<OCIE0A);
  50 }
  51
  52 inline
  53 void timer_clear(void)
  54 {
  55     uint8_t sreg = SREG;
  56     cli();
  57     timer_count = 0;
  58     SREG = sreg;
  59 }
  60
  61 inline
  62 uint16_t timer_read(void)
  63 {
  64     uint32_t t;
  65
  66     uint8_t sreg = SREG;
  67     cli();
  68     t = timer_count;
  69     SREG = sreg;
  70
  71     return (t & 0xFFFF);
  72 }
  73
  74 inline
  75 uint32_t timer_read32(void)
  76 {
  77     uint32_t t;
  78
  79     uint8_t sreg = SREG;
  80     cli();
  81     t = timer_count;
  82     SREG = sreg;
  83
  84     return t;
  85 }
  86
  87 inline
  88 uint16_t timer_elapsed(uint16_t last)
  89 {
  90     uint32_t t;
  91
  92     uint8_t sreg = SREG;
  93     cli();
  94     t = timer_count;
  95     SREG = sreg;
  96
  97     return TIMER_DIFF_16((t & 0xFFFF), last);
  98 }
  99
 100 inline
 101 uint32_t timer_elapsed32(uint32_t last)
 102 {
 103     uint32_t t;
 104
 105     uint8_t sreg = SREG;
 106     cli();
 107     t = timer_count;
 108     SREG = sreg;
 109
 110     return TIMER_DIFF_32(t, last);
 111 }
 112
 113 // excecuted once per 1ms.(excess for just timer count?)
 114 ISR(TIMER0_COMPA_vect)
 115 {
 116     timer_count++;
 117 }