//include the library code
#include <LiquidCrystal.h>
#include <Wire.h>

#define samp_siz 15
#define rise_threshold 8
#define beat_count 3
#define sensorPin A1
float avg,diff,reader,start,last,rise_count,beat;
int n;
long int now;
float reads[samp_siz],beat_time[beat_count],sum,heartrate;
bool rising;

// initialize the LCD library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

char str[16] = "Viva a corentena";

void setup() {
  Serial.begin(9600);
  pinMode(8,OUTPUT);
  digitalWrite(8,HIGH);

    // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  
  // Print a message to the LCD.
  lcd.print("Heartbeat Reader");
  for (int i = 0; i< 16; i++) {
    lcd.setCursor(i, 1);
    lcd.print(str[i]);
    delay(250);
    }

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

  // write message across LCD screen
  for (int i = 0; i< 16; i++) {
    lcd.setCursor(i, 1);
    lcd.print(" ");
    delay(100);
    }
}

void loop() {
      // read a 20ms period of data, calculate the average
      // this gets rid of the 50Hz noise from lighting in the room
     n = 0;
     start = millis();
     reader = 0.;
     do
     {
      reader += analogRead(sensorPin);
      n++;
      now=millis();
     }
     while (now<start+20);
     reader /= n;

      // do a samp_siz point running average to smoothe the data     
     avg=0.;
     for (int i=samp_siz-1;i>0;i--)
     {
      reads[i]=reads[i-1];
      avg += reads[i];
     }
     reads[0]=reader;
     avg += reader;
     avg /= samp_siz;

     if (avg > last) 
     {
      rise_count++;
      if(!rising && rise_count > rise_threshold)
      {
        rising = true;
        beat = avg;
        for (int i=beat_count-1;i>0;i--)
        {
          beat_time[i]=beat_time[i-1];
        }
        beat_time[0]=millis();
      } 
     } else {
        rising = false;
        rise_count = 0;
        beat = avg-2;
     }

     heartrate = 0.;
     for(int i=1;i<beat_count;i++)
     {
      heartrate += beat_time[i-1]-beat_time[i];     
     }
     heartrate /= (beat_count-1);
     heartrate = 60000 / heartrate;

     // output to LCD
     lcd.setCursor(0,0);
     lcd.print("HB: ");
     lcd.print(int(heartrate));

     // output to serial monitor
     Serial.print(reader-500);
     Serial.print('\t');
     Serial.print(avg-500);
     Serial.print('\t');
     Serial.print(beat-500);
     Serial.print('\t');
     Serial.print(heartrate);
     Serial.print('\n');

     last = avg; 
}