how serial comunication port list in arduino

i have a question. i would make a serial comunication with arduino device, for the comunication i would make a port list in the comunication. if i write "app.Property = serialport("COM3",9600,"Timeout",5)" its works but "app.Property = serialportlist("available")" but doesnt works. why did happen ? thanks before

this my full code

classdef arduino1 < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure         matlab.ui.Figure
        UIAxes           matlab.ui.control.UIAxes
        start            matlab.ui.control.Button
        stop             matlab.ui.control.Button
        export           matlab.ui.control.Button
        UITable          matlab.ui.control.Table
        HardwarePanel    matlab.ui.container.Panel
        GridLayout11     matlab.ui.container.GridLayout
        Refresh          matlab.ui.control.Button
        PortLabel        matlab.ui.control.Label
        PortList         matlab.ui.control.DropDown
        ConnLamp         matlab.ui.control.Lamp
        ConnectionLabel  matlab.ui.control.Label
    end

    
    properties (Access = private)
     %% define semua kebutuhan
        % Description
        Property 

        % colors
        GREEN_COLOR  = [0 1 0]
        RED_COLOR    = [1 0 0]
        
    end
    

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

        % Code that executes after component creation
        function startupFcn(app)
%           app.Property = serialportlist("available") %%error
            app.Property = serialport("COM3",9600,"Timeout",5) 
        end

        % Button pushed function: start
        function startButtonPushed(app, event)
            app.ConnLamp.Color = app.GREEN_COLOR;
            global val_stop val_data %%val_voltage val_const 
            val_stop 		= 0;
            val_sample 	        = 300;
            val_voltage 	= 0;
            val_count 	        = 1;
            while val_count <= val_sample
	        if val_stop == 1
		  break;
	        else
           	  ADC_value = str2double(readline(app.Property));
		  val_const(val_count) 	        = 5;
		  val_voltage(val_count) 	= ADC_value(1)*5/308;
		  plot(app.UIAxes,val_voltage);
		  app.UIAxes.XLim		= [0 val_count+50];
		  app.UIAxes.YLim		= [0 5.1];
                  
                  val_time(val_count) = val_count;

                  val_data = [val_voltage; val_time];
                  app.UITable.Data =val_data;

                  val_count = val_count + 1;
                  
 	       end
            end
        end

        % Button pushed function: stop
        function stopButtonPushed(app, event)
            app.ConnLamp.Color = app.RED_COLOR;
            global val_stop 
            val_stop = 1;
        end

        % Button pushed function: export
        function exportButtonPushed(app, event)
            global val_data
            writematrix(val_data','data.xls');
        end

        % Button pushed function: Refresh
        function RefreshButtonPushed(app, event)
            if license('test', 'instr_control_toolbox') %% not function
                % delete all serial port objets from MATLAB memory
                % (Instrument Control Toolbox required)
                delete(instrfind);
                % looking for available serial ports
                % (Instrument Control Toolbox required)
                p = instrhwinfo('serial');
                app.PortList.Items = p.AvailableSerialPorts;
            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 = 'UI Figure';

            % Create UIAxes
            app.UIAxes = uiaxes(app.UIFigure);
            title(app.UIAxes, 'Title')
            xlabel(app.UIAxes, 'X')
            ylabel(app.UIAxes, 'Y')
            app.UIAxes.Position = [24 32 410 279];

            % Create start
            app.start = uibutton(app.UIFigure, 'push');
            app.start.ButtonPushedFcn = createCallbackFcn(app, @startButtonPushed, true);
            app.start.Position = [25 328 118 26];
            app.start.Text = 'start';

            % Create stop
            app.stop = uibutton(app.UIFigure, 'push');
            app.stop.ButtonPushedFcn = createCallbackFcn(app, @stopButtonPushed, true);
            app.stop.Position = [152 328 118 26];
            app.stop.Text = 'stop';

            % Create export
            app.export = uibutton(app.UIFigure, 'push');
            app.export.ButtonPushedFcn = createCallbackFcn(app, @exportButtonPushed, true);
            app.export.Position = [463 32 145 32];
            app.export.Text = 'export to .xls';

            % Create UITable
            app.UITable = uitable(app.UIFigure);
            app.UITable.ColumnName = {'Column 1'; 'Column 2'};
            app.UITable.RowName = {};
            app.UITable.Position = [455 100 161 242];

            % Create HardwarePanel
            app.HardwarePanel = uipanel(app.UIFigure);
            app.HardwarePanel.Title = 'Hardware';
            app.HardwarePanel.Position = [24 370 246 92];

            % Create GridLayout11
            app.GridLayout11 = uigridlayout(app.HardwarePanel);
            app.GridLayout11.ColumnWidth = {'1x', '3x'};
            app.GridLayout11.Padding = [5 5 5 5];

            % Create Refresh
            app.Refresh = uibutton(app.GridLayout11, 'push');
            app.Refresh.ButtonPushedFcn = createCallbackFcn(app, @RefreshButtonPushed, true);
            app.Refresh.Layout.Row = 2;
            app.Refresh.Layout.Column = 2;
            app.Refresh.Text = 'Refresh';

            % Create PortLabel
            app.PortLabel = uilabel(app.GridLayout11);
            app.PortLabel.HorizontalAlignment = 'right';
            app.PortLabel.Layout.Row = 1;
            app.PortLabel.Layout.Column = 1;
            app.PortLabel.Text = 'Port';

            % Create PortList
            app.PortList = uidropdown(app.GridLayout11);
            app.PortList.Items = {};
            app.PortList.Editable = 'on';
            app.PortList.BackgroundColor = [1 1 1];
            app.PortList.Layout.Row = 1;
            app.PortList.Layout.Column = 2;
            app.PortList.Value = {};

            % Create ConnLamp
            app.ConnLamp = uilamp(app.UIFigure);
            app.ConnLamp.Position = [289 429 20.6 20.6];
            app.ConnLamp.Color = [1 0 0];

            % Create ConnectionLabel
            app.ConnectionLabel = uilabel(app.UIFigure);
            app.ConnectionLabel.Position = [320 427 123.6 24.3636363636364];
            app.ConnectionLabel.Text = 'Connection';

            % 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 = arduino1

            % Create UIFigure and components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.UIFigure)

            % Execute the startup function
            runStartupFcn(app, @startupFcn)

            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

Answer 1

[Walter Roberson]

app.Property = serialport("COM3",9600,"Timeout",5)

would set Property to a serialport object

app.Property = serialportlist("available")

would try to set Property to a string array. The string array is not certain to be scalar -- might be empty, might list multiple ports. And it is not a serialport.

Alternate code:

spl = serialportlist("available");
if isempty(spl)
    error('no serial ports available')
end
app.Property = serialport(spl(1),9600,"Timeout",5)

[Imam Pratama Setiady]

it works thanks for helping me sir

[Imam Pratama Setiady]

sir i have a question again, refresh button its works for refresh new com, but if start with new com

detection of sensor is error. why did happen ? thanks

this code for refreshbutton

function RefreshButtonPushed(app, event)
                % delete all serial port objets from MATLAB memory
                delete(instrfind); 
                % looking for available serial ports
                p = instrhwinfo('serial');
                app.PortList.Items = p.AvailableSerialPorts;
        end
    end

[Walter Roberson]

With what you posted it is not completely clear whether you call serialport() again after the user chooses a different entry?

[Imam Pratama Setiady]

No sir, i am not choses a different enrty, but try to change a arduino to other port then a refresh. The refresh is works can display change the port. But if i try to start again with the new port after refresh the result is error stringclient same pic 2