int UpperThreshold = 125;     //Thresholding of where to read "beats" based on your signal input
    int LowerThreshold = 100;
    int reading = 0;
    int BPM = 0;
    bool IgnoreReading = false;
    bool FirstPulseDetected = false;
    unsigned long FirstPulseTime = 0;
    unsigned long SecondPulseTime = 0;
    unsigned long PulseInterval = 0;


    void setup(){
      Serial.begin(74880);
    }


    void loop(){
      reading = analogRead(A0); 
      // Heart beat leading edge detected.
      if(reading > UpperThreshold && IgnoreReading == false){
        if(FirstPulseDetected == false){
          FirstPulseTime = millis();
          FirstPulseDetected = true;
        }
        else{
          SecondPulseTime = millis();
          PulseInterval = SecondPulseTime - FirstPulseTime;
          FirstPulseTime = SecondPulseTime;
        }
        IgnoreReading = true;
      }


      // Heart beat trailing edge detected.
      if(reading < LowerThreshold && reading > 2){
        IgnoreReading = false;
      }  


      BPM = (1.0/PulseInterval) * 60.0 * 1000;
      //Serial.println(A0);
      Serial.print("BPM = ");
      Serial.println(BPM);
  delayMicroseconds(3900); 
  {
  // read the input on analog pin 0:
  int sensorValue = analogRead(A0);
  // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
  float voltage = sensorValue;{
  // read the input on analog pin 0:
  //int sensorValue = analogRead(A0);
  // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
 
  // print out the value you read:
  Serial.println(voltage);
};
  // print out the value you read:
  Serial.println(voltage);
}
    }