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/* Copyright 2015 Jack Humbert
*
* 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, see <http://www.gnu.org/licenses/>.
*/
// Simple analog to digitial conversion
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <stdint.h>
#include "analog.h"
static uint8_t aref = (1 << REFS0); // default to AREF = Vcc
void analogReference(uint8_t mode) { aref = mode & 0xC0; }
// Arduino compatible pin input
int16_t analogRead(uint8_t pin) {
#if defined(__AVR_ATmega32U4__)
static const uint8_t PROGMEM pin_to_mux[] = {0x00, 0x01, 0x04, 0x05, 0x06, 0x07, 0x25, 0x24, 0x23, 0x22, 0x21, 0x20};
if (pin >= 12) return 0;
return adc_read(pgm_read_byte(pin_to_mux + pin));
#elif defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__)
if (pin >= 8) return 0;
return adc_read(pin);
#else
return 0;
#endif
}
// Mux input
int16_t adc_read(uint8_t mux) {
#if defined(__AVR_AT90USB162__)
return 0;
#else
uint8_t low;
ADCSRA = (1 << ADEN) | ADC_PRESCALER; // enable ADC
ADCSRB = (1 << ADHSM) | (mux & 0x20); // high speed mode
ADMUX = aref | (mux & 0x1F); // configure mux input
ADCSRA = (1 << ADEN) | ADC_PRESCALER | (1 << ADSC); // start the conversion
while (ADCSRA & (1 << ADSC))
; // wait for result
low = ADCL; // must read LSB first
return (ADCH << 8) | low; // must read MSB only once!
#endif
}
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