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

I am trying to make a GUI using App Designer that reads and graphs the voltage sensed by my Arduino Uno. When I type on the Command Window the following syntax, I get results.

a=arduino('COM5','uno')
readVoltage(a,'A0')

But when I place the same syntax in a callback function in the App Designer, the error message "Undefined function 'voltageRead' for input arguments of type 'double'." appears. Below is part of my code in the App Designer.

 properties (Access = private)
     stop;
     done=0;
     a;
     h;
     s;
     SetPoint;
     luxvolt;
 end


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

        % Code that executes after component creation
        function startupFcn(app)
            clear all;
            app.a = arduino('COM5','uno');
        end

                % Button pushed function: StartButton
        function StartButtonPushed(app, event)
            app.stop = false;
            
            
            
            app.h = animatedline(app.UIAxes);
            startTime = datetime('now');
            axis = gca;
            axis.YGrid ='on';
            axis.YLim = [0 5];
            
            while ~app.stop
                app.luxvolt = voltageRead(app.a, 'A4');
                
                %luxactual = (luxvolt - 1.4565) .* (2300 - 0) ./ (0.3519 - 1.4565) + 0;
                t = datetime('now') - startTime;
                addpoints(app.h,datenum(t),app.luxvolt);
                drawnow
                app.stop = app.done;
            end

[Walter Roberson]

You should never ever have a "clear all" call in a program

[Walter Roberson]

At the point you are having trouble, app.a is probably []

Answer 1

[Vimal Rathod]

It seems like you have used voltageRead instead of readVoltage function.