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; 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.
23 * This code implements a PWM input using ICP3.
25 * The initial use is to measure wind speed in the ULA/Ball summer intern
26 * project payload developed at Challenger Middle School.
29 volatile __data uint16_t ao_icp3_count = 0;
30 volatile __data uint16_t ao_icp3_last = 0;
32 uint16_t ao_icp3(void)
42 ao_pwmin_display(void) __reentrant
44 /* display the most recent value */
45 printf("icp 3: %5u\n", ao_icp3());
55 uint16_t ao_icp3_this = (hi <<8) | lo;
57 /* handling counter rollovers */
58 if (ao_icp3_this >= ao_icp3_last)
59 ao_icp3_count = ao_icp3_this - ao_icp3_last;
61 ao_icp3_count = ao_icp3_this + (65536 - ao_icp3_last);
62 ao_icp3_last = ao_icp3_this;
65 __code struct ao_cmds ao_pwmin_cmds[] = {
66 { ao_pwmin_display, "p\0PWM input" },
73 /* do hardware setup here */
74 TCCR3A = ((0 << WGM31) | /* normal mode, OCR3A */
75 (0 << WGM30)); /* normal mode, OCR3A */
76 TCCR3B = ((1 << ICNC3) | /* input capture noise canceler on */
77 (0 << ICES3) | /* input capture on falling edge (don't care) */
78 (0 << WGM33) | /* normal mode, OCR3A */
79 (0 << WGM32) | /* normal mode, OCR3A */
80 (3 << CS30)); /* clk/64 from prescaler */
84 TIMSK3 = (1 << ICIE3); /* Interrupt on input compare */
86 /* set the spike filter bit in the TCCR3B register */
88 ao_cmd_register(&ao_pwmin_cmds[0]);