#include <Wire.h> 

#define samp_siz 4
#define rise_threshold 5
#define irPts 10

// set up LEDs and transistor
int sensorPin = 1; 
int REDLed = 6;
int IRLed = 0;
int beatLed = 5;

int T = 20;              // slot milliseconds to read a value from the sensor

void setup() {
  // set the connection to computer and clear data:
//  Serial.begin(9600);
//  Serial.flush();

  // set up the arduino pins for I/O
  pinMode(sensorPin,INPUT);
  pinMode(REDLed,OUTPUT);
  pinMode(IRLed,OUTPUT);
  pinMode(beatLed,OUTPUT);

  // flash red LED to say hello
  for (int i=0;i<3;i++){
    digitalWrite(REDLed,HIGH);
    delay(1000);
    digitalWrite(REDLed,LOW);
    delay(1000);
  }

}

void loop() {

  // initialise some variables
  int n;
  float irSignal;
  float reads[samp_siz];
  float sum,start,last,before,first,second,third,print_value;
  int rise_count;
  bool rising;
  long int last_beat;
  float irZero=0;
  for (int i=0;i<irPts;i++) 
    {
      irZero+=analogRead(sensorPin);
    }
    irZero/=(irPts+1);
  
  while(1)
  {

  // turn on LED, read transistor signal
  digitalWrite(REDLed,LOW);
  digitalWrite(IRLed,HIGH);
  n=0;
  start = millis();
  irSignal = 0;
  do
  {
    irSignal += analogRead(sensorPin);
    n++;
  }
  while (millis() < start + T);
  irSignal /= n;
  sum = 0;
  for (int i=0;i<samp_siz-1;i++)
  {
    reads[i+1]=reads[i];
  }
  reads[0]=irSignal;
  for (int i=0;i<samp_siz;i++)
  {
    sum+=reads[i];
  }
  last = sum/samp_siz;

  // look for rising curve, indicating start of a heart beat
  if (last > before)
  {
    rise_count++;
    if (!rising && rise_count > rise_threshold)
    {
      rising = true;
          first = millis() - last_beat;
          last_beat = millis();

          // Calculate the weighed average of heartbeat rate
          // according to the three last beats
          print_value = 60000. / (0.4*first+0.3*second+0.3*third);
          if (print_value > 40 && print_value < 80) 
            {
              digitalWrite(beatLed,HIGH);
            }
          
          third = second;
          second = first;

/*          Serial.print(last-irZero);
          Serial.print(",");
          Serial.print(last-irZero);
          Serial.print(",");
          Serial.print(print_value);
*/          
    }
  } else {
    rising = false;
    rise_count = 0;
    digitalWrite(beatLed,LOW);

/*    Serial.print(last-irZero);
    Serial.print(",");
    Serial.print(0);
    Serial.print(",");
    Serial.print(print_value);
*/
  }
  before = last;
//  Serial.println();
  
  } // while(1)
}