timer.c

  1/*
  2Copyright 2011 Jun Wako <wakojun@gmail.com>
  3
  4This program is free software: you can redistribute it and/or modify
  5it under the terms of the GNU General Public License as published by
  6the Free Software Foundation, either version 2 of the License, or
  7(at your option) any later version.
  8
  9This program is distributed in the hope that it will be useful,
 10but WITHOUT ANY WARRANTY; without even the implied warranty of
 11MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12GNU General Public License for more details.
 13
 14You should have received a copy of the GNU General Public License
 15along 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 <util/atomic.h>
 21#include <stdint.h>
 22#include "timer_avr.h"
 23#include "timer.h"
 24
 25// counter resolution 1ms
 26// NOTE: union { uint32_t timer32; struct { uint16_t dummy; uint16_t timer16; }}
 27volatile uint32_t timer_count;
 28static uint32_t   saved_ms;
 29
 30/** \brief timer initialization
 31 *
 32 * FIXME: needs doc
 33 */
 34void timer_init(void) {
 35#if TIMER_PRESCALER == 1
 36    uint8_t prescaler = _BV(CS00);
 37#elif TIMER_PRESCALER == 8
 38    uint8_t prescaler = _BV(CS01);
 39#elif TIMER_PRESCALER == 64
 40    uint8_t prescaler = _BV(CS00) | _BV(CS01);
 41#elif TIMER_PRESCALER == 256
 42    uint8_t prescaler = _BV(CS02);
 43#elif TIMER_PRESCALER == 1024
 44    uint8_t prescaler = _BV(CS00) | _BV(CS02);
 45#else
 46#    error "Timer prescaler value is not valid"
 47#endif
 48
 49#if defined(__AVR_ATmega32A__)
 50    // Timer0 CTC mode
 51    TCCR0 = _BV(WGM01) | prescaler;
 52
 53    OCR0  = TIMER_RAW_TOP;
 54    TIMSK = _BV(OCIE0);
 55#elif defined(__AVR_ATtiny85__)
 56    // Timer0 CTC mode
 57    TCCR0A = _BV(WGM01);
 58    TCCR0B = prescaler;
 59
 60    OCR0A = TIMER_RAW_TOP;
 61    TIMSK = _BV(OCIE0A);
 62#else
 63    // Timer0 CTC mode
 64    TCCR0A = _BV(WGM01);
 65    TCCR0B = prescaler;
 66
 67    OCR0A  = TIMER_RAW_TOP;
 68    TIMSK0 = _BV(OCIE0A);
 69#endif
 70}
 71
 72/** \brief timer clear
 73 *
 74 * FIXME: needs doc
 75 */
 76inline void timer_clear(void) {
 77    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 78        timer_count = 0;
 79    }
 80}
 81
 82/** \brief timer save
 83 *
 84 * Set saved_ms to current time.
 85 */
 86void timer_save(void) {
 87    saved_ms = timer_read32();
 88}
 89
 90/** \brief timer restore
 91 *
 92 * Set timer_count to saved_ms
 93 */
 94void timer_restore(void) {
 95    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 96        timer_count = saved_ms;
 97    }
 98}
 99
100/** \brief timer read
101 *
102 * FIXME: needs doc
103 */
104inline uint16_t timer_read(void) {
105    uint32_t t;
106
107    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
108        t = timer_count;
109    }
110
111    return (t & 0xFFFF);
112}
113
114/** \brief timer read32
115 *
116 * FIXME: needs doc
117 */
118inline uint32_t timer_read32(void) {
119    uint32_t t;
120
121    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
122        t = timer_count;
123    }
124
125    return t;
126}
127
128/** \brief timer elapsed
129 *
130 * FIXME: needs doc
131 */
132inline uint16_t timer_elapsed(uint16_t last) {
133    uint32_t t;
134
135    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
136        t = timer_count;
137    }
138
139    return TIMER_DIFF_16((t & 0xFFFF), last);
140}
141
142/** \brief timer elapsed32
143 *
144 * FIXME: needs doc
145 */
146inline uint32_t timer_elapsed32(uint32_t last) {
147    uint32_t t;
148
149    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
150        t = timer_count;
151    }
152
153    return TIMER_DIFF_32(t, last);
154}
155
156// excecuted once per 1ms.(excess for just timer count?)
157#ifndef __AVR_ATmega32A__
158#    define TIMER_INTERRUPT_VECTOR TIMER0_COMPA_vect
159#else
160#    define TIMER_INTERRUPT_VECTOR TIMER0_COMP_vect
161#endif
162ISR(TIMER_INTERRUPT_VECTOR, ISR_NOBLOCK) {
163    timer_count++;
164}