I am trying to run a simple Led On and Off project using arduino and app designer. The program does seem to function however, the code has errors

This is the code I put under the callbacks for the push buttons:

function LedOnButtonPushed(app, event)

clear all;

global a;

a = arduino;

while(1)

writeDigitalPin(a,'D5',1)

end

end

function LedOffButtonPushed(app, event)

clear all;

global a;

a = arduino;

while(1)

writeDigitalPin(a,'D5',0)

end

end

These are the errors that I receive:

Error using testing/LedOffButtonPushed (line 45)

MATLAB connection to Mega2560 at COM4 exists in your workspace. To create a new connection, clear the existing object.

Error using asyncio.Stream/wait (line 183)

Error while evaluating Button PrivateButtonPushedFcn.

Undefined function 'writeDigitalPin' for input arguments of type 'double'.

Error in testing/LedOnButtonPushed (line 26)

writeDigitalPin(a,'D5',1)

Error while evaluating Button PrivateButtonPushedFcn.

%Your help will be appreciated thank you!

[Kekeletso Mlambo]

App file

Answer 1

[Prateek]

Hi Kekeletso,

The code snippets you have posted seem fine in themselves; perhaps the problem lies in the rest of the code.

For better assistance, I request you to post the app designer file and complete code, so I can assess the source of the error.

Regards,

Prateek

[Kekeletso Mlambo]

classdef LED_ONOFF < matlab.apps.AppBase

% Properties that correspond to app components

properties (Access = public)

UIFigure matlab.ui.Figure

OFFButton matlab.ui.control.Button

ONButton matlab.ui.control.Button

end

% Callbacks that handle component events

methods (Access = private)

% Button pushed function: ONButton

function ONButtonPushed(app, event)

clear all;

global a;

a = arduino;

Ledpin = 'D2';

while(1)

writeDigitalPin(a,Ledpin,1)

end

end

% Button pushed function: OFFButton

function OFFButtonPushed(app, event)

clear all;

global a;

a = arduino;

Ledpin = 'D2';

while(1)

writeDigitalPin(a,Ledpin,0)

end

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 ONButton

app.ONButton = uibutton(app.UIFigure, 'push');

app.ONButton.ButtonPushedFcn = createCallbackFcn(app, @ONButtonPushed, true);

app.ONButton.Tag = 'ON';

app.ONButton.Position = [180 296 100 22];

app.ONButton.Text = 'ON';

% Create OFFButton

app.OFFButton = uibutton(app.UIFigure, 'push');

app.OFFButton.ButtonPushedFcn = createCallbackFcn(app, @OFFButtonPushed, true);

app.OFFButton.Tag = 'OFF';

app.OFFButton.Position = [396 296 100 22];

app.OFFButton.Text = 'OFF';

% 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 = LED_ONOF2

% 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

[Prateek]

Thanks for sharing the code.

I have made some changes, as follows -

a) A private property "connObj" is declared (line 12) and placed in a StartupFcn called "initialize" (line 20). This property stores the Arduino object, which gets created when the app is launched. This ensures that callback functions have access to a single Arduino object.

b) The call back functions for buttons use "connObj" to change the state of "Ledpin". This operation does not need an infinite while loop and hence that has been removed (lines 31 and 38).

The edited app is attached here.

You may also want to refer to the following links for details on app designer-

1) Develop Apps Using App Designer - MATLAB & Simulink - MathWorks India

2) Share Data Within App Designer Apps - MATLAB & Simulink - MathWorks India

Hope this helps.

Regards,

Prateek

[Kekeletso Mlambo]

It's working perfectly thank you very much!