void welcome() {
  LiquidCrystal_I2C lcd(0x27, 20, 4);
  lcd.begin();
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("   Welcome to GSD   ");
  lcd.setCursor(0, 3);
  lcd.print("v1.0            -RTX");
  delay(3000);
  lcd.clear();
}