#define COIN_PIN 2

void setup()
{
  // Debugging output
  Serial.begin(9600);

  // set up the LCD's number of rows and columns:

  Serial.println("Ready...");
  
  pinMode(COIN_PIN, INPUT);
  attachInterrupt(0, coinISR, RISING);  // COIN wire connected to D2;
}


// total amount of money collected;
float money = 0.0;

// gets incremented by the ISR;
// gets reset when coin was recognized (after train of pulses ends);
volatile int pulses = 0;
volatile long timeLastPulse = 0;


// executed for every pulse;
void coinISR()
{
  pulses++;
  timeLastPulse = millis();
}


void loop()
{

  long timeFromLastPulse = millis() - timeLastPulse;
  if (pulses > 0 && timeFromLastPulse > 200)
  {
    // sequence of pulses stopped; determine the coin type;
    if (pulses == 2)
    {
      Serial.println("Received dime (2 pulses)");
      money += .1;
    }
    else if (pulses == 5)
    {
      Serial.println("Received quarter (5 pulses)");
      money += .25;
    }
    else if (pulses == 10)
    {
      Serial.println("Received looney (10 pulses)");
      money += 1.0;
    }
    else if (pulses == 15)
    {
      Serial.println("Received tooney (15 pulses)");
      money += 2.0;
    }
    else
    {
      Serial.print("Unknown coin: ");
      Serial.print(pulses);
      Serial.println(" pulses");
    }

    pulses = 0;
  }
}