tmk_core/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 #ifdef TIMSK0
  50     TIMSK0 = (1<<OCIE0A);
  51 #else
  52     TIMSK = (1<<OCIE0A);
  53 #endif
  54 }
  55
  56 inline
  57 void timer_clear(void)
  58 {
  59     uint8_t sreg = SREG;
  60     cli();
  61     timer_count = 0;
  62     SREG = sreg;
  63 }
  64
  65 inline
  66 uint16_t timer_read(void)
  67 {
  68     uint32_t t;
  69
  70     uint8_t sreg = SREG;
  71     cli();
  72     t = timer_count;
  73     SREG = sreg;
  74
  75     return (t & 0xFFFF);
  76 }
  77
  78 inline
  79 uint32_t timer_read32(void)
  80 {
  81     uint32_t t;
  82
  83     uint8_t sreg = SREG;
  84     cli();
  85     t = timer_count;
  86     SREG = sreg;
  87
  88     return t;
  89 }
  90
  91 inline
  92 uint16_t timer_elapsed(uint16_t last)
  93 {
  94     uint32_t t;
  95
  96     uint8_t sreg = SREG;
  97     cli();
  98     t = timer_count;
  99     SREG = sreg;
 100
 101     return TIMER_DIFF_16((t & 0xFFFF), last);
 102 }
 103
 104 inline
 105 uint32_t timer_elapsed32(uint32_t last)
 106 {
 107     uint32_t t;
 108
 109     uint8_t sreg = SREG;
 110     cli();
 111     t = timer_count;
 112     SREG = sreg;
 113
 114     return TIMER_DIFF_32(t, last);
 115 }
 116
 117 // excecuted once per 1ms.(excess for just timer count?)
 118 ISR(TIMER0_COMPA_vect)
 119 {
 120     timer_count++;
 121 }