common/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.h"
  22
  23
  24 // counter resolution 1ms
  25 // NOTE: union { uint32_t timer32; struct { uint16_t dummy; uint16_t timer16; }}
  26 volatile uint32_t timer_count = 0;
  27
  28 void timer_init(void)
  29 {
  30     // Timer0 CTC mode
  31     TCCR0A = 0x02;
  32
  33 #if TIMER_PRESCALER == 1
  34     TCCR0B = 0x01;
  35 #elif TIMER_PRESCALER == 8
  36     TCCR0B = 0x02;
  37 #elif TIMER_PRESCALER == 64
  38     TCCR0B = 0x03;
  39 #elif TIMER_PRESCALER == 256
  40     TCCR0B = 0x04;
  41 #elif TIMER_PRESCALER == 1024
  42     TCCR0B = 0x05;
  43 #else
  44 #   error "Timer prescaler value is NOT vaild."
  45 #endif
  46
  47     OCR0A = TIMER_RAW_TOP;
  48     TIMSK0 = (1<<OCIE0A);
  49 }
  50
  51 inline
  52 void timer_clear(void)
  53 {
  54     uint8_t sreg = SREG;
  55     cli();
  56     timer_count = 0;
  57     SREG = sreg;
  58 }
  59
  60 inline
  61 uint16_t timer_read(void)
  62 {
  63     uint32_t t;
  64
  65     uint8_t sreg = SREG;
  66     cli();
  67     t = timer_count;
  68     SREG = sreg;
  69
  70     return (t & 0xFFFF);
  71 }
  72
  73 inline
  74 uint32_t timer_read32(void)
  75 {
  76     uint32_t t;
  77
  78     uint8_t sreg = SREG;
  79     cli();
  80     t = timer_count;
  81     SREG = sreg;
  82
  83     return t;
  84 }
  85
  86 inline
  87 uint16_t timer_elapsed(uint16_t last)
  88 {
  89     uint32_t t;
  90
  91     uint8_t sreg = SREG;
  92     cli();
  93     t = timer_count;
  94     SREG = sreg;
  95
  96     return TIMER_DIFF_16((t & 0xFFFF), last);
  97 }
  98
  99 inline
 100 uint32_t timer_elapsed32(uint32_t last)
 101 {
 102     uint32_t t;
 103
 104     uint8_t sreg = SREG;
 105     cli();
 106     t = timer_count;
 107     SREG = sreg;
 108
 109     return TIMER_DIFF_32(t, last);
 110 }
 111
 112 // excecuted once per 1ms.(excess for just timer count?)
 113 ISR(TIMER0_COMPA_vect)
 114 {
 115     timer_count++;
 116 }