Smart Kegerator

  /*
                               +-----+
 *                  +----------| USB |----------+
 *                  |          +-----+       *  |
 *                  | [ ] VIN           3V3 [ ] |
 *                  | [ ] GND           RST [ ] |
 *                  | [ ] TX           VBAT [ ] |
 *                  | [ ] RX  [S]   [R] GND [*] |
 *                  | [ ] WKP            D7 [ ] |
 *                  | [ ] DAC +-------+  D6 [ ] |    
 *                  | [*] A5  |   *   |  D5 [ ] |    
 *                  | [*] A4  |Photon |  D4 [ ] |<-------- Toggle switch Power
 *                  | [ ] A3  |       |  D3 [ ] |        |
 *                  | [ ] A2  +-------+  D2 [ ] |        \ 
 *                  | [ ] A1             D1 [ ] |        | 
 *                  | [ ] A0             D0 [*] |<-------- Toggle Switch Common
 *                  |                           |
 *                   \    []         [______]  /
 *                    \_______________________/
 *
 *
 */
 //declaration of variables
    int reading = D0;
    int power = D4;
    int tap;
    int long totaltime = 0;
    int long pourtime = 0;
    int FlowRate =(1.6);
    long int Volume = 0; 
  
 

void setup() {     
	Serial1.begin(230400); //enables usb serial debugging if plugged into PC.
    pinMode(power, OUTPUT);  //sets D4 pin to an analog voltage output
    pinMode(reading, INPUT);  // D0 is set to a voltagee input
    digitalWrite(power, HIGH); //Sets D4 analog value to high
  
    Particle.variable("tap", &tap, INT);    // Shows on particle app when tap is open(0)/closed(1)
    Particle.variable("Volume", &Volume, INT);					//Shows on particle app as total volume dispensed
    Particle.variable("Totaltime", &totaltime, INT);      //Shows on particle app the total time the tap has been opened
}

void loop() {
	
	tap = digitalRead(reading);  //enables you to watch this via the particle variable.
	pourtime = 0; //pourtime needs to be reset every loop.  this would cause your error to increase each loop without reset.
    pourtime = pulseIn(reading,LOW); //pulseIn function acts as a timer every time the D0 pin becomes low (i.e. tap is opened)
    // pourtime is recorded
 
	totaltime = pourtime + totaltime; //This equation takes previous loop's totaltime and adds in most recent pourtime
    Volume = ((FlowRate) * (totaltime*2))/1000000; //Calculates total volume dispensed by multipling totaltime and flow rate
    //totaltime is multiplied by 2 due to total time being recorded asw half the actual value
   //Volume is divided by 1000000 to account for pulseIn function measuring in microseconds
     
	if (pourtime > 0){  //When tap open D0 pin goes to 0
		
		Particle.publish("Pouring","The tap is open.",PUBLIC);    //Notifies user when tap is opened
	
	    if (Volume >= 5){  //If total volume dispenses is >= to 80% of keg volume
			Particle.publish("Volume","Low",PUBLIC); //event published to tell the other particle the volume is low
			//This volume can vary based on size of the keg and requires a simple reflashing of the particle
		}
		}
	}