void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode (2, OUTPUT);
  }

void loop() {
  // put your main code here, to run repeatedly:
  //Serial.println(analogRead(34));
  // ADC 12 bit, 0 - 2^12 -1 = 4095
  digitalWrite(2, HIGH);  // built in LED = D2
  delay(100);
  digitalWrite(2, LOW);
  delay(100);
}