The code which disconnect safely an USB drive works randomly

Dear all,

I work on MATLAB R2023a and Windows 11 23H2.

Thanks to this post I coud do the following code which disconnect safely E:, a USB drive.

Unfortunately, sometimes it does not work, for example, when I change the plug from USB port, it needs several execution to disconnect safely the drive.

I also noticed that in the app (see below), missing run are more frequent. The code is just executed under the button Run (first callback).

The command window shows the message I expect when it works but in fact the USB drive is still visible on "My Computer". If the disconnection works, I see an error message in the command window.

Do you have an idea what can I do to solve this issue or find it origin?

Best regards,

Pierre

The code:

function EjectUSB
    % Create the PowerShell command to eject the drive
    powershellCommand = '(New-Object -comObject Shell.Application).Namespace(17).ParseName(''E:'').InvokeVerb(''Eject'')';
    
    % Create the command to run PowerShell from MATLAB
    command = sprintf('powershell -Command "%s"', powershellCommand);
    
    % Execute the PowerShell command
    [status, cmdout] = system(command);
    
    % Display the results
    if status == 0
        disp(['Lecteur USB E éjecté avec succès.']);
    else
        disp('Échec de l''éjection du lecteur USB.');
        disp(cmdout);
    end
end

%Add a diskpart list to check if E: has been removed

The app:

classdef PotVibrantUI < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure                     matlab.ui.Figure
        AmplitudeSlider              matlab.ui.control.Slider
        FrequencySlider              matlab.ui.control.Slider
        Amplitude0to1EditField       matlab.ui.control.NumericEditField
        Amplitude0to1EditFieldLabel  matlab.ui.control.Label
        FrequencyHzEditField         matlab.ui.control.NumericEditField
        FrequencyHzEditFieldLabel    matlab.ui.control.Label
        RunButton                    matlab.ui.control.Button
    end

    
    properties (Access = private)
        frequency = 20; % Default frequency value
        amplitude = 0.5; % Default amplitude value
    end
    

    % Callbacks that handle component events
    methods (Access = private)

        % Button pushed function: RunButton
        function RunButtonPushed(app, event)
            SetupFileCreation(app.frequency) 
            CustomFileCreation(app.amplitude)
            pause(3)
            EjectUSB
            pause(3)
            EjectUSB
        end

        % Value changing function: FrequencySlider
        function FrequencySliderValueChanging(app, event)
            changingValue = event.Value;
            app.FrequencyHzEditField.Value = changingValue;
            % Update the app.frequency property
            app.frequency = changingValue;
            % guidata() to share variables
        end

        % Value changed function: FrequencyHzEditField
        function FrequencyHzEditFieldValueChanged(app, event)
            value = app.FrequencyHzEditField.Value;
            app.FrequencySlider.Value = value;
            % Update the app.frequency property
            app.frequency = value;
        end

        % Value changing function: AmplitudeSlider
        function AmplitudeSliderValueChanging(app, event)
            changingValue = event.Value;
            app.Amplitude0to1EditField.Value = changingValue;
            % Update the app.frequency property
            app.amplitude = changingValue;
            % guidata() to share variables
        end

        % Value changed function: Amplitude0to1EditField
        function Amplitude0to1EditFieldValueChanged(app, event)
            value = app.Amplitude0to1EditField.Value;
            app.AmplitudeSlider.Value = value;
            app.amplitude = value;
        end
    end

    % Component initialization
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 640 480];
            app.UIFigure.Name = 'MATLAB App';

            % Create RunButton
            app.RunButton = uibutton(app.UIFigure, 'push');
            app.RunButton.ButtonPushedFcn = createCallbackFcn(app, @RunButtonPushed, true);
            app.RunButton.FontSize = 24;
            app.RunButton.Position = [26 41 568 80];
            app.RunButton.Text = 'Run';

            % Create FrequencyHzEditFieldLabel
            app.FrequencyHzEditFieldLabel = uilabel(app.UIFigure);
            app.FrequencyHzEditFieldLabel.HorizontalAlignment = 'right';
            app.FrequencyHzEditFieldLabel.FontSize = 24;
            app.FrequencyHzEditFieldLabel.Position = [49 435 170 31];
            app.FrequencyHzEditFieldLabel.Text = 'Frequency (Hz)';

            % Create FrequencyHzEditField
            app.FrequencyHzEditField = uieditfield(app.UIFigure, 'numeric');
            app.FrequencyHzEditField.ValueChangedFcn = createCallbackFcn(app, @FrequencyHzEditFieldValueChanged, true);
            app.FrequencyHzEditField.FontSize = 24;
            app.FrequencyHzEditField.Position = [234 434 100 32];
            app.FrequencyHzEditField.Value = 20;

            % Create Amplitude0to1EditFieldLabel
            app.Amplitude0to1EditFieldLabel = uilabel(app.UIFigure);
            app.Amplitude0to1EditFieldLabel.HorizontalAlignment = 'right';
            app.Amplitude0to1EditFieldLabel.FontSize = 24;
            app.Amplitude0to1EditFieldLabel.Position = [38 252 195 31];
            app.Amplitude0to1EditFieldLabel.Text = 'Amplitude (0 to 1)';

            % Create Amplitude0to1EditField
            app.Amplitude0to1EditField = uieditfield(app.UIFigure, 'numeric');
            app.Amplitude0to1EditField.ValueChangedFcn = createCallbackFcn(app, @Amplitude0to1EditFieldValueChanged, true);
            app.Amplitude0to1EditField.FontSize = 24;
            app.Amplitude0to1EditField.Position = [248 251 100 32];
            app.Amplitude0to1EditField.Value = 0.5;

            % Create FrequencySlider
            app.FrequencySlider = uislider(app.UIFigure);
            app.FrequencySlider.Limits = [10 40];
            app.FrequencySlider.ValueChangingFcn = createCallbackFcn(app, @FrequencySliderValueChanging, true);
            app.FrequencySlider.FontSize = 24;
            app.FrequencySlider.Position = [26 418 473 3];
            app.FrequencySlider.Value = 20;

            % Create AmplitudeSlider
            app.AmplitudeSlider = uislider(app.UIFigure);
            app.AmplitudeSlider.Limits = [0 1];
            app.AmplitudeSlider.MajorTicks = [0 0.125 0.25 0.375 0.5 0.625 0.75 0.875 1];
            app.AmplitudeSlider.ValueChangingFcn = createCallbackFcn(app, @AmplitudeSliderValueChanging, true);
            app.AmplitudeSlider.FontSize = 18;
            app.AmplitudeSlider.Position = [20 207 479 3];
            app.AmplitudeSlider.Value = 0.5;

            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end

    % App creation and deletion
    methods (Access = public)

        % Construct app
        function app = PotVibrantUI

            % Create UIFigure and components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.UIFigure)

            if nargout == 0
                clear app
            end
        end

        % Code that executes before app deletion
        function delete(app)

            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
end

Answer 1

[Divyanshu]

Hi Pierre,

A possible reason for the above code working randomly to eject USB, can be because of the function 'EjectUSB'.

Although the callback attached to 'Run' button might be triggered every time you click the button in the App but because of the improper functioning of 'EjectUSB' function issue occurs.

You can modify the logic of 'EjectUSB' function and can use 'diskpart' utility as specified in the edited part of the original solution:

https://superuser.com/questions/1547316/eject-connected-external-hard-drive-using-cmd

Hope it helps!

Answer 2

[Pierre]

Hi Divyanshu,

Thanks a lot for your suggestion. I found out that "remove all dismount" is a little bit too strong, it actually delete the letter of the drive so it is not detected anymore in the explorer.

See what happen below:

So, when I plug the USB again, Diskpart detect it as Volume 5 but not the explorer. I have to assign a letter again:

Best regards,

Pierre