2 * Copyright © 2009 Keith Packard <keithp@keithp.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, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
14 * You should have received a copy of the GNU General Public License along
15 * with this program; if not, write to the Free Software Foundation, Inc.,
16 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
21 volatile __data uint16_t ao_tick_count;
23 uint16_t ao_time(void)
32 #define T1_CLOCK_DIVISOR 8 /* 24e6/8 = 3e6 */
33 #define T1_SAMPLE_TIME 30000 /* 3e6/30000 = 100 */
36 volatile __data uint8_t ao_adc_interval = 1;
37 volatile __data uint8_t ao_adc_count;
43 ISR(TIMER1_COMPA_vect)
47 if (++ao_adc_count == ao_adc_interval) {
56 ao_timer_set_adc_interval(uint8_t interval) __critical
58 ao_adc_interval = interval;
66 TCCR1A = ((0 << WGM11) | /* CTC mode, OCR1A */
67 (0 << WGM10)); /* CTC mode, OCR1A */
68 TCCR1B = ((0 << ICNC1) | /* no input capture noise canceler */
69 (0 << ICES1) | /* input capture on falling edge (don't care) */
70 (0 << WGM13) | /* CTC mode, OCR1A */
71 (1 << WGM12) | /* CTC mode, OCR1A */
72 (3 << CS10)); /* clk/64 from prescaler */
75 OCR1A = 2500; /* 16MHz clock */
77 OCR1A = 1250; /* 8MHz clock */
80 TIMSK1 = (1 << OCIE1A); /* Interrupt on compare match */