2 Copyright 2011 Jun Wako <wakojun@gmail.com>
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.
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.
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/>.
23 #ifndef TIMER_PRESCALER
25 # define TIMER_PRESCALER 256
26 # elif F_CPU >= 4000000
27 # define TIMER_PRESCALER 64
29 # define TIMER_PRESCALER 8
32 #define TIMER_RAW_FREQ (F_CPU/TIMER_PRESCALER)
33 #define TIMER_RAW TCNT0
34 #define TIMER_RAW_TOP (TIMER_RAW_FREQ/1000)
36 #if (TIMER_RAW_TOP > 255)
37 # error "Timer0 can't count 1ms at this clock freq. Use larger prescaler."
40 #define TIMER_DIFF(a, b, max) ((a) >= (b) ? (a) - (b) : (max) - (b) + (a))
41 #define TIMER_DIFF_RAW(a, b) TIMER_DIFF(a, b, UINT8_MAX)
42 #define TIMER_DIFF_MS(a, b) TIMER_DIFF(a, b, UINT16_MAX)
45 extern volatile uint16_t timer_count;
48 void timer_init(void);
49 void timer_clear(void);
50 uint16_t timer_read(void);
51 uint16_t timer_elapsed(uint16_t last);