private void OpenClicked(object sender, RoutedEventArgs e)
        {
            serialLayer.OpenPort(PortComboBox.SelectedItem.ToString());
            OpenButton.IsEnabled  = false;
            CloseButton.IsEnabled = true;

            DLRadioButton.IsChecked = true;
            Thread.Sleep(50);
            ModeChanged(null, null); // przejscie w tryb DL po otworzeniu portu
        }