// Define hardware connections
#define PIN_GATE_IN 2
#define IRQ_GATE_IN 0
#define PIN_LED_OUT 13
#define PIN_ANALOG_IN A0

// soundISR()
// This function is installed as an interrupt service routine for the pin
// change interrupt. When digital input 2 changes state, this routine
// is called.
// It queries the state of that pin, and sets the onboard LED to reflect that 
// pin's state.
void soundISR()
{
 int pin_val;

 pin_val = digitalRead(PIN_GATE_IN);
 digitalWrite(PIN_LED_OUT, pin_val); 
}

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

 // Configure LED pin as output
 pinMode(PIN_LED_OUT, OUTPUT);

 // configure input to interrupt
 pinMode(PIN_GATE_IN, INPUT);
 attachInterrupt(IRQ_GATE_IN, soundISR, CHANGE);

 // Display status
 Serial.println("Initialized");
}

void loop()
{
 int value;

 // Check the envelope input
 value = analogRead(PIN_ANALOG_IN);

 // Convert envelope value into a message
 Serial.print(value);
 Serial.print("Status: ");
 if(value <= 100)
 {
 Serial.println("Quiet.");
 }
 else if( (value > 100) && ( value <= 300) )
 {
 Serial.println("Moderate.");
 }
 else if(value > 300)
 {
 Serial.println("Loud.");
 }

 // pause for 1 second
 delay(1000);
}