/*
  Kleines Programm mit LCD
  Board: Arduino Nano
  SDA => A4
  SCL => A5
*/

byte Minuten = 0;
byte Sekunden = 0;
bool TimerStart = false;

#include <Wire.h> 
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,2);  // I2C Addresse 0x27, 16 Zeichen und 2 Zeilen

void setup(){
  pinMode (2, INPUT);
  digitalWrite (2, HIGH);
  attachInterrupt (digitalPinToInterrupt(2), InterruptServiceRoutine, FALLING);

  Serial.begin(9600);

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("System Start");
  for (byte a=0;a<5;a++){
    lcd.print(".");
    delay (500);
  }
  delay (500);
  lcd.setCursor(0,0);
  lcd.print("                ");
  lcd.setCursor(0,0);
  lcd.print(" Timer Stopp");
}

void loop() {

  while (TimerStart == false){
    delay (1);
  }
  
  for (Minuten=0; Minuten<4; Minuten++){
    for (Sekunden=0; Sekunden<6; Sekunden++)
      Serial.print (Minuten);
      Serial.print (":");
      Serial.println (Sekunden);
      delay (1000);
  }
}

void InterruptServiceRoutine (){
  if (TimerStart == false){
    lcd.setCursor(1,0);
    lcd.print ("Start");
    TimerStart = true;
  }
  if (TimerStart == true){
    TimerStart = false;
    lcd.print (" Stop");
  }
}