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/*
* Pneumatic pressure controller.
* Sensor input.
*
* Copyright (C) 2008-2009 Michael Buesch <mb@bu3sch.de>
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include "sensor.h"
#include "util.h"
#include "remote.h"
#include <avr/io.h>
#include <avr/interrupt.h>
static struct sensor *active_sensor;
#define ADC_MAX U32(0x3FF)
ISR(ADC_vect)
{
struct sensor *s = active_sensor;
const uint16_t full_scale_adc = ADC_MAX * (uint32_t)s->full_scale_mv / 5000;
uint16_t adc, mv, mbar;
/* Convert the ADC value to millivolts. */
adc = ADC;
if (adc > full_scale_adc)
adc = full_scale_adc;
mv = (uint32_t)s->full_scale_mv * (uint32_t)adc / full_scale_adc;
/* Subtract the sensor voltage offset, so 0 mBar results in 0 mV. */
if (mv > s->mv_offset)
mv -= s->mv_offset;
else
mv = 0;
mbar = (uint32_t)s->full_scale_mbar * (uint32_t)mv / (uint32_t)s->full_scale_mv;
sensor_result(s, mbar);
}
static inline void adc_trigger(uint8_t mux, bool with_irq)
{
/* Set the multiplexer to ADC-0, AVcc Ref. */
ADMUX = (1 << REFS0) | mux;
/* Start ADC with a prescaler of 128. That's a ADC freq
* of 125kHz on a 16MHz crystal. */
ADCSRA = (1 << ADEN) | (1 << ADSC) |
(1 << ADPS0) | (1 << ADPS1) | (1 << ADPS2) |
(with_irq ? (1 << ADIE) : 0);
}
void sensor_trigger_read(struct sensor *s)
{
active_sensor = s;
mb();
/* Trigger an ADC conversion with interrupt notification. */
adc_trigger(s->adc_mux, 1);
}
void sensor_retrigger(void)
{
/* Retrigger an ADC conversion on the currently active sensor. */
adc_trigger(active_sensor->adc_mux, 1);
}
void sensor_init(struct sensor *s)
{
mdelay(20); /* Warm-up time */
/* Discard the first ADC result. */
adc_trigger(s->adc_mux, 0);
while (ADCSRA & (1 << ADSC))
mb();
}
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