Sound sensor on A0 and pin 3, on an Arduino Uno

// Sound sensor module: how loud, and is it over the line?
//
//   module AO -> A0   module DO -> pin 3   VCC -> 5V   GND -> GND
//   the Uno's own LED on pin 13 shows the digital output
//
// The module has a microphone and two outputs. AO is the microphone's level,
// amplified, for analogRead(). DO is a comparator: it goes HIGH when the level
// passes the threshold set by the little screw on the module, and LOW again
// when it falls back.
//
// Drag the sound level on the module to make some noise.

const int ANALOG_PIN = A0;
const int DIGITAL_PIN = 3;
const int LED = 13;

void setup() {
  pinMode(DIGITAL_PIN, INPUT);
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: sound sensor on A0 and pin 3");
}

void loop() {
  int level = analogRead(ANALOG_PIN);
  bool loud = digitalRead(DIGITAL_PIN) == HIGH;
  digitalWrite(LED, loud ? HIGH : LOW);
  Serial.print("level ");
  Serial.print(level);
  Serial.println(loud ? "  loud" : "");
  delay(200);
}