int sample;
unsigned long time1;
unsigned long time2;
unsigned long peak;
unsigned long lastpeak;
unsigned long gap;
unsigned long BPM = 0;
int state = 1;
void setup() {
  Serial.begin(115200); // initialize the serial communication:
  pinMode(A0, INPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
}
void loop() {
  while (state == 1) {
    while (analogRead(0) < 450) {
      Serial.println(analogRead(0));
      digitalWrite(7, HIGH);
      digitalWrite(6, LOW);
      delay(20);
    }
    state = 2;
  }
  while (state == 2) {
    time1 = millis();
    state = 3;
  }
  while (state == 3) {
    while (analogRead(0) < 460) {
      Serial.println(analogRead(0));
      digitalWrite(7, HIGH);
      digitalWrite(6, LOW);
      delay(20);
    }
    state = 4;
  }
  while (state == 4) {
    while (analogRead(0) > 450) {
      Serial.println(analogRead(0));
      digitalWrite(6, HIGH);
      digitalWrite(7, LOW);
      delay(20);
    }
    state = 5;
  }
  while (state == 5) {
    time2 = millis();
    peak = (time1 + time2) / 2;
    gap = peak - lastpeak;
    BPM = 60000 / gap;
    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////


    //This is where I would put in my moving average and code to display
    //BPM is the variable name used for beats per minute
    //The threshold value in this code is 450. You can change this value to suit your heart monitor.
    //You may need to use a potentiometer to make the threshold a variable.
    //If you do this then you need to make sure you are constantly reading in the analog value from the pot

    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

    //UNCOMMENT THIS CODE IF YOU WANT TO PLOT THE HEART SIGNAL AND BPM AT THE SAME TIME
    //Serial.print(analogRead(0));
    //Serial.print("\t");
    //Serial.println(BPM);
    lastpeak = peak;
    state = 6;
  }
  while (state == 6) {
    while (analogRead(0) > 440) {
      Serial.println(analogRead(0));
      digitalWrite(6, HIGH);
      digitalWrite(7, LOW);
      delay(20);
    }
    state = 1;
  }
}