private async void streamSwitch_Toggled(object sender, RoutedEventArgs e) {
            int aCount = 0; // Callback counter

            var model = (DataContext as MainViewModel).MyModel;

            if (streamSwitch.IsOn)
            {
                back.IsEnabled = false; // Disable the back button
                metawear.OnUnexpectedDisconnect = async () =>
                {
                    Console.WriteLine("Unexpectedly lost connection");
                    var dialog = new MessageDialog("Unexpectedly lost Bluetooth connection - exit & restart program", "Bluetooth Connection lost");
                    dialog.Options = MessageDialogOptions.None;
                    dialog.Commands.Add(new UICommand("OK", cmd => { }));
                    dialog.DefaultCommandIndex = 0;
                    dialog.CancelCommandIndex = 0;
                    await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => dialog.ShowAsync());
                };


                // Make sure the Q's are empty ...
                IMUDataQ.Clear();

                tokenSource = new CancellationTokenSource();
                dpCT = tokenSource.Token;

                // Kick off the task to process pairs of datum ....
                dpTask = Task.Run(() => ProcessData(dpCT, false, 1));   // Run the Processing task on the new IMUDataQ data until cancelled

                // Set up the device ...

                sensorFusion = metawear.GetModule<ISensorFusionBosch>();
                sensorFusion.Configure(Mode.Ndof, AccRange._2g, GyroRange._250dps);
              
                // Set up the callback function for Linear Acceleration data stream ...
                await sensorFusion.LinearAcceleration.AddRouteAsync(source => source.Stream(data => {
                    FusedIMUPen datum;

                    datum.IMU.tStamp = data.Timestamp;
                    datum.IMU.LinearAcc = data.Value<Acceleration>();

                    IMUDataQ.Enqueue(datum);

                }));


                ILed led = metawear.GetModule<ILed>();
                led.EditPattern(MbientLab.MetaWear.Peripheral.Led.Color.Red, Pattern.Solid);

                // Now that the callback is set up start the data stream on the device ...
                sensorFusion.LinearAcceleration.Start();
                sensorFusion.Start();
                led.Play();
            }
            else {
                // Streaming is switched off ...
                sensorFusion.Stop();
                sensorFusion.LinearAcceleration.Stop();

                var led = metawear.GetModule<ILed>();
                led.Stop(true);

                // Tell the processing task to finish ...
                Thread.Sleep(100);
                tokenSource.Cancel();
                await dpTask ;

                // Tidy up the resources on the device
                metawear.TearDown();
                back.IsEnabled = true;  // Enable the Back button
                FusePenDataButton.IsEnabled = true;
            }
        }