adc.ino

void setup() {
  Serial.begin(9600);
  initADC();
}

void loop() {
  Serial.println(readADC());
}

void initADC() {
  ADMUX |= (1 << REFS0) | (1 << ADLAR); // ADLAR -> ADCH, ADCL 왼쪽 정렬
}

byte readADC() {
  ADCSRA |= (1 << ADSC);  // start conversion
  while(ADCSRA & (1 << ADIF));  // interrupt flag <- when conversion completed

  uint8_t high;
  high = ADCH;  // read only 1 byte

  return high;
}