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- // 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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