// 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 }