1 /* Copyright 2015 Jack Humbert
3 * This program is free software: you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation, either version 2 of the License, or
6 * (at your option) any later version.
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
13 * You should have received a copy of the GNU General Public License
14 * along with this program. If not, see <http://www.gnu.org/licenses/>.
17 // Simple analog to digitial conversion
20 #include <avr/pgmspace.h>
25 static uint8_t aref = (1<<REFS0); // default to AREF = Vcc
28 void analogReference(uint8_t mode)
34 // Arduino compatible pin input
35 int16_t analogRead(uint8_t pin)
37 #if defined(__AVR_ATmega32U4__)
38 static const uint8_t PROGMEM pin_to_mux[] = {
39 0x00, 0x01, 0x04, 0x05, 0x06, 0x07,
40 0x25, 0x24, 0x23, 0x22, 0x21, 0x20};
41 if (pin >= 12) return 0;
42 return adc_read(pgm_read_byte(pin_to_mux + pin));
43 #elif defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__)
44 if (pin >= 8) return 0;
52 int16_t adc_read(uint8_t mux)
54 #if defined(__AVR_AT90USB162__)
59 ADCSRA = (1<<ADEN) | ADC_PRESCALER; // enable ADC
60 ADCSRB = (1<<ADHSM) | (mux & 0x20); // high speed mode
61 ADMUX = aref | (mux & 0x1F); // configure mux input
62 ADCSRA = (1<<ADEN) | ADC_PRESCALER | (1<<ADSC); // start the conversion
63 while (ADCSRA & (1<<ADSC)) ; // wait for result
64 low = ADCL; // must read LSB first
65 return (ADCH << 8) | low; // must read MSB only once!