/*
Program made by Daniele Mari on 8.04.2024
*/

#include <LiquidCrystal_I2C.h>

//  Variables

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int PulseWire = 0;       // PulseSensor PURPLE WIRE connected to ANALOG PIN 0
const int LED = LED_BUILTIN;   // The on-board Arduino LED, close to PIN 13.
int Threshold = 520;           // Determine which Signal to "count as a beat" and which to ignore.
int mean_signal [50] = {0};    // mean of the signal to determine threshold
int i = 0;                     // variable for increment
int j = 0;                     // variable for increment
long temp = 0;                 // temporary variable for the threshold

int Signal;                   // Signal of the sensor
unsigned long Time_now = 0;   // actual time
unsigned long Time_old = 0;   // old time
double interval_time_s = 0;   // interval between 2 pulse
unsigned int BPM = 0;         // Pulse per minute
bool wait_next = false;       // will wait to be under the threshold before to look again for pulse

void setup() {  

  Serial.begin(9600);   // For Serial Monitor
  lcd.init();           // init lcd
  lcd.backlight();      // turn on the backlight
  lcd.clear();          // clear the LCD (avoid to have any old thing to be printed on lcd)
}


void loop() {

Signal = analogRead(PulseWire);   // read the sensor signal
Serial.println(Signal);           // print the signal into plotter

// do the mean for new threshold
mean_signal [i] = Signal;
i++;

if(i>49) {
  for(i = 0; i<=49; i++) {
    temp += mean_signal [i];
  }
  Threshold = temp/50 + 20;
  temp = 0;
  i = 0;
}
//****************************

// If the signal is above threshold, then "turn-on" Arduino's on-Board LED and calculate BPM
if(Signal > Threshold && !wait_next) {
    digitalWrite(LED,HIGH);
    Time_now = millis();
    interval_time_s = (Time_now - Time_old);

    // avoid value out of range
    if (interval_time_s > 300)  {
      BPM = (1/(interval_time_s/1000))*60;
      Time_old = Time_now;
      wait_next = true;
      lcd.setCursor(0, 0);
      lcd.print("BPM :    ");
      lcd.setCursor(6, 0);
      lcd.print(BPM);

      // set up RGB led color
     
    }
   } 
   
   else {
     digitalWrite(LED,LOW);     //  if sensor signal is below threshold, "turn-off" internal LED.
     wait_next = false;
   }

  delay(20);                    // small idle time to not overkill micro-controller

}