Arduino clearing existing connection issue

Question

Borian Spassov 2019-6-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468189-arduino-clearing-existing-connection-issue

回答： shaherbano zaidi 2023-9-15

I have declared a global object arduino() and in a different function I would like to clear this connection and create another. It keeps saying that the connection to arduino is existing eventhough I use "clearvars -global a".

Error: "MATLAB connection to Uno at COM3 exists in your workspace. To create a new connection, clear the existing object."

    function ClearArduino(app)
            clearvars -global a
            
            a = arduino('COM3', 'Uno');   %Error is on this line
            
            writeDigitalPin(a, 'D11', 0);
            writeDigitalPin(a, 'D12', 0);
            writeDigitalPin(a, 'D13', 0);
        end
        
	 function runArduinoCode(app, indicator)
				
            clearvars -global a
            
            a = arduino('COM3', 'Uno');
            
            while indicator == "On"
 
                writeDigitalPin(a, 'D11', 1);
                pause(0.5)
                writeDigitalPin(a, 'D11', 0);
                
                writeDigitalPin(a, 'D12', 1);
                pause(0.5)
                writeDigitalPin(a, 'D12', 0);
                
                writeDigitalPin(a, 'D13', 1);
                pause(0.5)
                writeDigitalPin(a, 'D13', 0);
                
            end
            
            clear a;
       end
	   

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Laura Letellier 2021-4-28

编辑：Laura Letellier 2021-4-28

Did anyone ever find a solution for this?

My students are encountering this issue and the only way we can 100% clear the existing object is to exit MATLAB, unlpug the Arduino, replug, and restart MATLAB.

If any of the MATLAB software developers are monitoring this, please tell us how to even see the workspace when using App Designer and then give us a hint as to how to clear the connection. Since you are throwing the error you must have some way to access the associated pointer, handle, or hwind to know that the connection is unavailable. If so there must be a way for us to programmatically release it.

Thank you!

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Answer 1

Geoff Hayes 2019-6-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468189-arduino-clearing-existing-connection-issue#answer_380273

编辑：Geoff Hayes 2019-6-21

在 MATLAB Online 中打开

Borian - why not define a property in your app that represents the arduino object so that all callbacks have access to it? See Share Data Within App Designer Apps for details. Presumably you would do something like

properties (Access = private)
        arduinoObject = [] % arduino object
end

and your callbacks (?) would become something like

function ClearArduino(app)
    if ~isempty(app.arduinoObject)
        clear(app.arduinoObject);
    end
    app.arduinoObject = arduino('COM3', 'Uno');
    
    writeDigitalPin(app.arduinoObject, 'D11', 0);
    writeDigitalPin(app.arduinoObject, 'D12', 0);
    writeDigitalPin(app.arduinoObject, 'D13', 0);
end
function runArduinoCode(app, indicator)
    if ~isempty(app.arduinoObject)
        clear(app.arduinoObject);
    end
    app.arduinoObject = arduino('COM3', 'Uno');
    
    while indicator == "On"
    
        writeDigitalPin(app.arduinoObject, 'D11', 1);
        pause(0.5)
        writeDigitalPin(app.arduinoObject, 'D11', 0);
        
        writeDigitalPin(app.arduinoObject, 'D12', 1);
        pause(0.5)
        writeDigitalPin(app.arduinoObject, 'D12', 0);
        
        writeDigitalPin(app.arduinoObject, 'D13', 1);
        pause(0.5)
        writeDigitalPin(app.arduinoObject, 'D13', 0);
        
    end
end