Arduino clearing existing connection issue

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Borian Spassov
Borian Spassov il 21 Giu 2019
Risposto: shaherbano zaidi il 15 Set 2023
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
  1 Commento
Laura Letellier
Laura Letellier il 28 Apr 2021
Modificato: Laura Letellier il 28 Apr 2021
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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Risposte (2)

Geoff Hayes
Geoff Hayes il 21 Giu 2019
Modificato: Geoff Hayes il 21 Giu 2019
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
I have no idea if the above will work but it may be something to start with.
  3 Commenti
franck tinkeu
franck tinkeu il 21 Apr 2021
We Can try " clear Arduino" at the Window command
franck tinkeu
franck tinkeu il 21 Apr 2021
We Can try it before beginning the next programm!!!

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shaherbano zaidi
shaherbano zaidi il 15 Set 2023
I was encountering the same issue i just added "Clear all' at the top of my code.

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