Undefined function error for readDistance function within GUI editor

I am using the function readDistance() with an Arduino and HC - SR04 ultrasonic sensor. I have tested it in the command line to ensure my equipment is working and successfully received the distance value. However, for my assignment, I need to create a GUI and get the data there. When I try to use it in the GUI editor, I get the following error: 'Undefined function 'readDistance' for input arguments of type 'double'. '

I am using it in this context:

        function CollectDataButtonPushed(app, event)
            data = zeros(1e4,1);
            t = zeros(1e4,1);
            i = 1;
            tic
            while toc < 10
                value = readDistance(app.us);
                data(i) = value;
                data(i) = data(i) * 100;    %convert from m to cm
                t(i) = toc;
                i = i + 1;
            end
            plot(app.UIAxes, data);

            %writetable(T,filename);
        end

I have declared and set up my Arduino and sensor like this:

    properties (Access = private)
        a % arduino
        us % ultrasound sensor
    end

    app.a = arduino('COM4', 'Uno', "Libraries", "Ultrasonic");
    app.us = app.a.ultrasonic('D7','D6');

I have also tried to use the function like the following, but I get an error that says 'Dot indexing is not supported for variables of this type.'

    value = app.us.readDistance();

I have tried searching for this error, but all I can find are the pages on how to use the readDistance() function which don't offer specific help.

Answer 1

[Marisa Assink]

I was able to figure it out, it was a problem with my ISP (Xfinity). Works fine with no edits on different networks, or at home with the wifi off on my laptop.

Answer 2

[Hornett]

Hi Marisa,

I understand that you are unable to use the function “readDistance()” with an Arduino and HC - SR04 ultrasonic sensor, I believe that you have defined the ultrasonic object in an incorrect way, to define it correctly you should use the following syntax:

app.us = ultrasonic(app.a, ‘D7’, ‘D6’ ). 

In this code snippet,‘app.a’represents the arduino object,'D7'is the trigger pin, and'D6'is the echo pin.

Please find the documentation of the “ultrasonic” function below:

https://www.mathworks.com/help/supportpkg/arduinoio/ref/arduinoio.ultrasonic.html

Hope this helps!