MATLAB app designer, how to update value of a property in declared callback function

Hello all,

I am rather new to MATLAB, and therefore a little unfamiliar with the app designer, apologies in advance.

I am trying to write a code that tracks the position of a stepper motor over serial communication. Currently, I have the setup such that it will callback the readSerialData Function everytime the terminator "CR" is reached.

Ideally I would like to access the value read. I wanted to save this value to the motorPos property of the app for use in separate functions later down the line. However, from tests, it seems that the value of app.motorPos does not update and remains the initial value of 0, as defined in the startup function. While it does display the correct value in the command window (from the disp(app.arduino) function), the value of the property app.arduino seem to remain 0, when called upon in later functions.

How should I go about updating the value of property motorPos?

Thanks,

Yuandi Wu

properties (Access = public)
        arduino 
        motorPos
    end
    
    methods (Access = private)
        
        function readSerialData(app,src)
            app.motorPos = readline(src);
            disp(app.motorPos);
        end
    end
    

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

        % Code that executes after component creation
        function startupFcn(app)

            delete(instrfindall); 
            app.arduino = serialport ("COM3", 9600, "Timeout", 0.1);
            app.arduino.DataBits = 8;
            configureTerminator(app.arduino,"CR")
            configureCallback(app.arduino,"terminator",@readSerialData)
            
            %initially, upon startup, display these values
            app.motorPos = '0';
            disp(app.motorPos)
            
        end

[Michael Van de Graaff]

does this help? https://www.mathworks.com/matlabcentral/answers/555832-how-to-configure-serialport-callback-in-app-designer?s_tid=answers_rc1-2_p2_MLT

Maybe this would work?

configureCallback(app.arduino,"terminator",@(src) readSerialData(app,src))

[Yuandi Wu]

Hello,

I have attempted to implement the code and it seems to be working!

Thank you so much for your response, I really appreciate it! Definitely saved me for this assignment!

Answer 1

[Michael Van de Graaff]

I put the following in a comment, and OP says it worked, so i'm copying this into an answer in the hopes that it can be accepted officially

------------------------------------------

does this help? https://www.mathworks.com/matlabcentral/answers/555832-how-to-configure-serialport-callback-in-app-designer?s_tid=answers_rc1-2_p2_MLT

Maybe this would work?

configureCallback(app.arduino,"terminator",@(src) readSerialData(app,src))

Answer 2

[Mohammad Sami]

You can try the following.

            configureCallback(app.arduino,"terminator",@app.readSerialData)

[Yuandi Wu]

Hello,

Thank you so much for taking the time to reply, I have tried this solution, and unfortunately, was met with this error. This error was displayed on the command window, whereas before it would have displayed the location.

Unfortunately, it also seems that it did not save the value as a property, as when used in later call back functions, there were no response. In the previous code, it would treat the motorPos as 0, and move it as such, however now it does not move at all. I think that it is overwriting the motorPos and updating it, but maybe just not with the desired value due to the error?

What would be your take on this?

Thanks again,

Yuandi Wu

Warning: Error occurred while executing the listener callback for event DataWritten defined for class
asyncio.InputStream:
Error using TestApp2/readSerialData
Too many input arguments.

Error in TestApp2>@(varargin)app.readSerialData(varargin{:}) (line 53)
            configureCallback(app.arduino,"terminator",@app.readSerialData)

Error in internal.Serialport/callbackFunction (line 1406)
            obj.BytesAvailableFcn(obj, dataAvailableInfo);

Error in internal.Serialport>@(varargin)obj.callbackFunction(varargin{:}) (line 957)
                        obj.StringClient.StringReadFcn = @obj.callbackFunction;

Error in matlabshared.transportclients.internal.StringClient.StringClient/DataAvailableCallback

Error in
matlabshared.transportclients.internal.StringClient.StringClient>@(varargin)obj.DataAvailableCallback(varargin{:})

Error in matlabshared.seriallib.internal.Serial/onDataReceived

Error in matlabshared.seriallib.internal.Serial>@(varargin)obj.onDataReceived(varargin{:})

Error in asyncio.Channel/onDataReceived (line 487)
                notify(obj.InputStream, 'DataWritten', ...

Error in asyncio.Channel>@(source,data)obj.onDataReceived() (line 425)
                                         @(source, data) obj.onDataReceived()); 
> In asyncio/Channel/onDataReceived (line 487)
In asyncio.Channel>@(source,data)obj.onDataReceived() (line 425) 
>> 

[Alessandro Livi]

2 year later and still no definitive answer that works

Pick one or offer yet another that works:

function SerInput(app,src)

function SerInput(~,src)

Pick one or offer yet another that works: (MyCom is the serial port handle

app.MyCom.configureCallback("terminator",@SerInput);

configureCallback(app.MyCom,"terminator",@SerInput);

configureCallback(app.MyCom,"terminator",@app.MyInput); % answer 555832

% As recommended by staff in answer 555832 below above

configureCallback(app.MyCom,"terminator",@(src) MyInput(app,src));

Tried last option: App Designer is now stopping debug (returning to >Run) leaving my app running and NO error message there or in Command Window when I get a char from the MyCom