#include <LiquidCrystal.h> //Libraries
LiquidCrystal lcd(2, 3, 4, 5, 6, 7); //Arduino pins to lcd

#define bt_start  A0
#define bt_stop   A1
#define bt_reset  A2

int hh = 0, mm = 0, ss = 0, ms = 0;
bool timerStart = false;


void setup() {

  pinMode(bt_start, INPUT_PULLUP);
  pinMode(bt_stop,  INPUT_PULLUP);
  pinMode(bt_reset, INPUT_PULLUP);

  lcd.begin(16, 2); // Configura lcd numero columnas y filas
  lcd1.clear();
  lcd.setCursor (0, 0);
  lcd.print("  Welcome  To  ");
  lcd.setCursor (0, 1);
  lcd.print("   Stopwatch   ");
  delay(2000);
  lcd.clear();


  // ===========Init Interruption ============================
  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);
  // ==========================================================
}

void loop() {

  if (digitalRead (bt_start) == 0) {
    timerStart = true; // Start stopwatch
  }

  if (digitalRead (bt_stop) == 0) {
    timerStart = false; // Stop stopwatch
  }

  if (digitalRead (bt_reset) == 0) {
    ms = 0, ss = 0, mm = 0, hh = 0; // Reset stopwatch
  }


  // ===== gestion TEMPS ====
  if (ms > 999) {
    ms = 0; ss = ss + 1;
    if (ss > 59) {
      ss = 0;
      mm = mm + 1;
    }
    if (mm > 59) {
      mm = 0;
      hh = hh + 1;
    }
  }
  // =======================


  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);
}


// =====  Routine d'interruption =====
ISR(TIMER1_COMPA_vect) {
  if (timerStart == true) {
    ms = ms + 1;
  }
}
// ===================================