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/*
* Copyright © 2012 Robert D. Garbee <robert@gag.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, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#include "ao.h"
#include "ao_pwmin.h"
/*
* This code implements a PWM input using ICP3.
*
* The initial use is to measure wind speed in the ULA/Ball summer intern
* project payload developed at Challenger Middle School.
*/
volatile __data uint16_t ao_icp3_count = 0;
volatile __data uint16_t ao_icp3_last = 0;
uint16_t ao_icp3(void)
{
uint16_t v;
ao_arch_critical(
v = ao_icp3_count;
);
return v;
}
static void
ao_pwmin_display(void) __reentrant
{
/* display the most recent value */
printf("icp 3: %5u\n", ao_icp3());
}
ISR(TIMER3_CAPT_vect)
{
uint8_t lo = ICR3L;
uint8_t hi = ICR3H;
uint16_t ao_icp3_this = (hi <<8) | lo;
/* handling counter rollovers */
if (ao_icp3_this >= ao_icp3_last)
ao_icp3_count = ao_icp3_this - ao_icp3_last;
else
ao_icp3_count = ao_icp3_this + (65536 - ao_icp3_last);
ao_icp3_last = ao_icp3_this;
}
__code struct ao_cmds ao_pwmin_cmds[] = {
{ ao_pwmin_display, "p\0PWM input" },
{ 0, NULL },
};
void
ao_pwmin_init(void)
{
/* do hardware setup here */
TCCR3A = ((0 << WGM31) | /* normal mode, OCR3A */
(0 << WGM30)); /* normal mode, OCR3A */
TCCR3B = ((1 << ICNC3) | /* input capture noise canceler on */
(0 << ICES3) | /* input capture on falling edge (don't care) */
(0 << WGM33) | /* normal mode, OCR3A */
(0 << WGM32) | /* normal mode, OCR3A */
(3 << CS30)); /* clk/64 from prescaler */
TIMSK3 = (1 << ICIE3); /* Interrupt on input compare */
/* set the spike filter bit in the TCCR3B register */
ao_cmd_register(&ao_pwmin_cmds[0]);
}
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