#include <LiquidCrystal_I2C.h>

//initialize lcd
LiquidCrystal_I2C lcd(0x27,16,2);


#define startstopPin  3
#define resetPin  2
#define startstopLED  4

byte startstopState = LOW;
byte oldstartstopState = LOW;
byte start = false;

int hh=0, mm=0, ss=0, ms=0; 

void setup() { // put your setup code here, to run once 

pinMode(startstopPin, INPUT_PULLUP);
pinMode(resetPin,  INPUT_PULLUP);
pinMode(startstopLED, OUTPUT);

lcd.init();
lcd.backlight();

lcd.clear();
lcd.setCursor (0,0);
lcd.print("  FYP Wear Rig  ");
lcd.setCursor (0,1);
lcd.print("   Stopwatch   ");
delay(2000);
lcd.clear();
 

 noInterrupts();         // disable all interrupts
 TCCR1A = 0;             // set entire TCCR1A register to 0  //set timer1 interrupt at 1kHz  // 1 ms
 TCCR1B = 0;             // same for TCCR1B
 TCNT1  = 0;             // set timer count for 1khz increments
 OCR1A = 1999;           // = (16*10^6) / (1000*8) - 1
 //had to use 16 bit timer1 for this bc 1999>255, but could switch to timers 0 or 2 with larger prescaler
 // turn on CTC mode
 TCCR1B |= (1 << WGM12); // Set CS11 bit for 8 prescaler
 TCCR1B |= (1 << CS11);  // enable timer compare interrupt
 TIMSK1 |= (1 << OCIE1A);
 interrupts();           // enable

}

void loop() {
startstopState = digitalRead(startstopPin);
if(startstopState != oldstartstopState){
  oldstartstopState = startstopState;
  if(startstopState == LOW){
    start = (start == true) ? false: true;
  }
}


if(digitalRead (resetPin) == LOW && start == false){ 
ms=0, ss=0, mm=0, hh=0; // Reset stopwatch 
delay(100);
}

lcd.setCursor (0,0);
lcd.print("   Stopwatch   ");

lcd.setCursor (2,1);
lcd.print((hh/10)%10);
lcd.print(hh%10);
lcd.print(":");
lcd.print((mm/10)%10);
lcd.print(mm%10);
lcd.print(":");
lcd.print((ss/10)%10);
lcd.print(ss%10);
lcd.print(":");
lcd.print((ms/100)%10);
lcd.print((ms/10)%10);
lcd.print(ms%10);

if(start==true){
digitalWrite(startstopLED, HIGH); // Turn LED on.  
}else{
digitalWrite(startstopLED, LOW); // Turn LED off.    
}
  
}


ISR(TIMER1_COMPA_vect){   
if(start == true){
  ms=ms+1;
if(ms>999){ms=0;ss=ss+1;
if(ss>59){ss=0; mm=mm+1;}
if(mm>59){mm=0; hh=hh+1;}
  }  
 }
}