2 * Copyright © 2012 Robert D. Garbee <robert@gag.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; version 2 of the License.
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
22 * This code implements a PWM input using ICP3.
24 * The initial use is to measure wind speed in the ULA/Ball summer intern
25 * project payload developed at Challenger Middle School.
28 volatile __data uint16_t ao_tick3_count;
31 ao_pwmin_display(void) __reentrant
35 uint16_t value = (hi <<8) | lo;
39 uint16_t value3 = (hi3 <<8) | lo3;
41 /* now display the value we read */
42 printf("timer 1: %5u %2x %2x\n", value, hi, lo);
43 printf("timer 3: %5u %2x %2x\n", value3, hi3, lo3);
46 ISR(TIMER3_COMPA_vect)
51 __code struct ao_cmds ao_pwmin_cmds[] = {
52 { ao_pwmin_display, "p\0PWM input" },
59 /* do hardware setup here */
60 TCCR3A = ((0 << WGM31) | /* normal mode, OCR3A */
61 (0 << WGM30)); /* normal mode, OCR3A */
62 TCCR3B = ((0 << ICNC3) | /* no input capture noise canceler */
63 (0 << ICES3) | /* input capture on falling edge (don't care) */
64 (0 << WGM33) | /* normal mode, OCR3A */
65 (0 << WGM32) | /* normal mode, OCR3A */
66 (4 << CS30)); /* clk/256 from prescaler */
68 OCR3A = 1250; /* 8MHz clock */
70 TIMSK3 = (1 << OCIE3A); /* Interrupt on compare match */
72 /* set the spike filter bit in the TCCR3B register */
74 ao_cmd_register(&ao_pwmin_cmds[0]);