summaryrefslogtreecommitdiff
path: root/platforms/avr/timer.c
blob: 9fb671ae8d88321d01e54b11138ee5d6713fe0a2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
/*
Copyright 2011 Jun Wako <wakojun@gmail.com>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/atomic.h>
#include <stdint.h>
#include "timer_avr.h"
#include "timer.h"

// counter resolution 1ms
// NOTE: union { uint32_t timer32; struct { uint16_t dummy; uint16_t timer16; }}
volatile uint32_t timer_count;

/** \brief timer initialization
 *
 * FIXME: needs doc
 */
void timer_init(void) {
#if TIMER_PRESCALER == 1
    uint8_t prescaler = _BV(CS00);
#elif TIMER_PRESCALER == 8
    uint8_t prescaler = _BV(CS01);
#elif TIMER_PRESCALER == 64
    uint8_t prescaler = _BV(CS00) | _BV(CS01);
#elif TIMER_PRESCALER == 256
    uint8_t prescaler = _BV(CS02);
#elif TIMER_PRESCALER == 1024
    uint8_t prescaler = _BV(CS00) | _BV(CS02);
#else
#    error "Timer prescaler value is not valid"
#endif

#if defined(__AVR_ATmega32A__)
    // Timer0 CTC mode
    TCCR0 = _BV(WGM01) | prescaler;

    OCR0  = TIMER_RAW_TOP;
    TIMSK = _BV(OCIE0);
#elif defined(__AVR_ATtiny85__)
    // Timer0 CTC mode
    TCCR0A = _BV(WGM01);
    TCCR0B = prescaler;

    OCR0A = TIMER_RAW_TOP;
    TIMSK = _BV(OCIE0A);
#else
    // Timer0 CTC mode
    TCCR0A = _BV(WGM01);
    TCCR0B = prescaler;

    OCR0A  = TIMER_RAW_TOP;
    TIMSK0 = _BV(OCIE0A);
#endif
}

/** \brief timer clear
 *
 * FIXME: needs doc
 */
inline void timer_clear(void) {
    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
        timer_count = 0;
    }
}

/** \brief timer read
 *
 * FIXME: needs doc
 */
inline uint16_t timer_read(void) {
    uint32_t t;

    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
        t = timer_count;
    }

    return (t & 0xFFFF);
}

/** \brief timer read32
 *
 * FIXME: needs doc
 */
inline uint32_t timer_read32(void) {
    uint32_t t;

    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
        t = timer_count;
    }

    return t;
}

/** \brief timer elapsed
 *
 * FIXME: needs doc
 */
inline uint16_t timer_elapsed(uint16_t last) {
    uint32_t t;

    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
        t = timer_count;
    }

    return TIMER_DIFF_16((t & 0xFFFF), last);
}

/** \brief timer elapsed32
 *
 * FIXME: needs doc
 */
inline uint32_t timer_elapsed32(uint32_t last) {
    uint32_t t;

    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
        t = timer_count;
    }

    return TIMER_DIFF_32(t, last);
}

// excecuted once per 1ms.(excess for just timer count?)
#ifndef __AVR_ATmega32A__
#    define TIMER_INTERRUPT_VECTOR TIMER0_COMPA_vect
#else
#    define TIMER_INTERRUPT_VECTOR TIMER0_COMP_vect
#endif
ISR(TIMER_INTERRUPT_VECTOR, ISR_NOBLOCK) {
    timer_count++;
}