/* Touch Light
   based on the knock tutorial from arduino.cc:
  * http://www.arduino.cc/en/Tutorial/Knock
  * by DojoDave <http://www.0j0.org>
 */

int pins[] = { 9,10,11 }; // Putting the LED pins in an array
int num_pins = 3;

int knockSensor = 0;     // knock sensor is plugged into analog pin 0
byte val = 0;            // variable to store the value read from the sensor pin
int THRESHOLD = 10;      // threshold value to decide when the detected sound is a *ping* or not
int onLED;               // variable to record which LED is on

void setup() {

  int i;
  for (i = 0; i < num_pins; i++)
    pinMode(pins[i], OUTPUT);      // set each pin as an output

  Serial.begin(9600);
  
  digitalWrite(pins[0], 1);        // turning the first LED on
  onLED = 1;
}

void loop() {
  val = analogRead(knockSensor);     // reading the sensor
  if (val >= THRESHOLD) {

    int i;
    for (i = 0; i < num_pins; i++)
      digitalWrite(pins[i], 0);      // turning off any LED that is on

    int randomLED = int(random(3));  // picking a random LED
    if (randomLED == onLED) {        // if it picks the same pin, it will choose a different one
      if (onLED == 0)
        randomLED = 1;
      if (onLED == 1)
        randomLED = 2;
      if (onLED == 2)
        randomLED = 0;
    }

    digitalWrite(pins[randomLED], 1);  // turn on the random LED
    onLED = randomLED;
    
    Serial.println("*ping*");
  }
  delay(100);
}