int bien_tro = A0;

void setup() {
  pinMode(bien_tro,INPUT);
  Serial.begin(9600);
}

void loop() {
  int value = analogRead(bien_tro);
  Serial.print("Dien ap: ");
  //int voltage = value /1023.0 * 5.0;
  float voltage = value /1023.0 * 5.0;
  Serial.print(voltage);
  Serial.println(" volt");
  delay(200);
}