#include <LiquidCrystal_I2C.h>
int btnstart = 27;
int btnstop = 26;
int stopuhr = 0;
int sekunden = 0;
int minuten = 0;
int stunden = 0;

LiquidCrystal_I2C LCD = LiquidCrystal_I2C(0x27,16,2);

void setup() {
  Serial.begin(100);
  pinMode(btnstart, INPUT);
  pinMode(btnstop, INPUT);
  LCD.init();
  LCD.backlight();
  LCD.setCursor(0,0);
  LCD.print("KRONES Stopuhr");
  LCD.setCursor(0,1);
  LCD.print(stunden);
  LCD.print(":");
  LCD.print(minuten);
  LCD.print(":");
  LCD.print(sekunden);
  LCD.print(" ");
} 

void loop() {

  if(digitalRead(btnstart)==HIGH){
    Serial.println("Uhr ein");
    stopuhr=1;
  }

  while(stopuhr==1){
  sekunden++;

  LCD.setCursor(0,1);
  LCD.print(stunden);
  LCD.print(":");
  LCD.print(minuten);
  LCD.print(":");
  LCD.print(sekunden);
  LCD.print(" ");

  if(sekunden==59){
    sekunden=0;
    minuten++;
  }
  if(minuten==59 && sekunden==59){
    minuten=0;
    stunden++;
  }
  
  delay(100);
  if(digitalRead(btnstop)==HIGH){
    Serial.println("Uhr aus");
    stopuhr=0;
  }
  }
  delay(100);
}