Cannot close connection. MATLAB connection to Due at COM9 exists in your workspace. To create a new connection, clear the existing object.

Question

Jason 2019-9-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480775-cannot-close-connection-matlab-connection-to-due-at-com9-exists-in-your-workspace-to-create-a-new

回答： saleh said bouhliga 2020-9-20

采纳的回答： Jason

在 MATLAB Online 中打开

I cannot close the ports of the arduino after a GUIDE GUI program.

All the commands I have tried at the exit function are:

try
    myArduinoAddonLibrary = getappdata(0,'ARD_AD');
    clear myArduinoAddonLibrary;
    arduinoObj = getappdata(0,'ARD');
    fclose(serial(arduinoObj.Port));
    delete(serial(arduinoObj.Port))
    clear arduinoObj;
catch errorObj
    errordlg(getReport(errorObj,'extended','hyperlinks','off'),'Arduino Error');
end

What would I be doing wrong?

The error that appears when I try to create another Arduino connection in the same port is:

 MATLAB connection to Due at COM9 exists in your workspace. To create a new connection, clear the existing object

For MATLAB 2019a

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Jason 2019-9-17

在 MATLAB Online 中打开

However, I have noticed that if I click the exit task several times, the ports duplicate? What could this be?

Instrument Object Array
   Index:    Type:     Status:   Name:  
   1         serial    closed    Serial-COM9
   2         serial    closed    Serial-COM9
   3         serial    closed    Serial-COM9

At the end of the exit task, I now run

clear all

to make sure no variables are left in the GUI workspace. And the error has now changed to:

 "Unable to create a communication link with the serial port. Please check your input argument PORT..."

However, MATLAB crashes with an internal error.

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Answer 1

Jason 2019-9-17

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480775-cannot-close-connection-matlab-connection-to-due-at-com9-exists-in-your-workspace-to-create-a-new#answer_392279

在 MATLAB Online 中打开

We solved it using this:

try
    clear
    myArduinoAddonLibrary = getappdata(0,'ARD_AD');
    clear myArduinoAddonLibrary;
    arduinoObj = getappdata(0,'ARD');
    fclose(serial(arduinoObj.Port));
    delete(serial(arduinoObj.Port))
    clear arduinoObj;
catch errorObj
    errordlg(getReport(errorObj,'extended','hyperlinks','off'),'Arduino Error');
end
%Remove appdata from memory
rmappdata(0,'ARD')
rmappdata(0,'ARD_AD')
clear all;

We just added clear at the start made sure the workspace was totally clear at the end.

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Answer 2

saleh said bouhliga 2020-9-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480775-cannot-close-connection-matlab-connection-to-due-at-com9-exists-in-your-workspace-to-create-a-new#answer_497470

In the MatLab Help Center they had nice description of how to clear a variable from memory. Check it here: https://www.mathworks.com/help/matlab/ref/clearvars.html

In your case should be: clearvars -global a;