gui_mainfcn(gui_State, varargin{:});

I want to extract data from Arduino, transfer it to Matlab via Bluetooth, and create an interface using GUI. But when I click any button on the GUI, I get the following error.

Error using project>connect_Callback

Connection to this device already exists in the

workspace.

See related documentation for troubleshooting steps.

Error in gui_mainfcn (line 95)

feval(varargin{:});

Error in project (line 17)

gui_mainfcn(gui_State, varargin{:});

Error in matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)project('connect_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating UIControl Callback.

I can't figure out what exactly is the problem. Am I doing something wrong ?

Here is my code:

function varargout = project(varargin)
    gui_Singleton = 1;
    gui_State = struct('gui_Name', mfilename, ...
        'gui_Singleton', gui_Singleton, ...
        'gui_OpeningFcn', @project_OpeningFcn, ...
        'gui_OutputFcn', @project_OutputFcn, ...
        'gui_LayoutFcn', [] , ...
        'gui_Callback', []);

    if nargin && ischar(varargin{1})
        gui_State.gui_Callback = str2func(varargin{1});
    end

    if nargout
        [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
    else
        gui_mainfcn(gui_State, varargin{:});
    end

% --- Executes just before project is made visible.
function project_OpeningFcn(hObject, eventdata, handles, varargin)
    handles.output = hObject;
    handles.TempGraph = plot(0, 0, 'r'); % Temperature graph
    handles.HumGraph = plot(0, 0, 'b'); % Humidity graph
    handles.connection = []; % Bluetooth connection
    guidata(hObject, handles);

% --- Outputs from this function are returned to the command line.
function varargout = project_OutputFcn(hObject, eventdata, handles)
    varargout{1} = handles.output;

% --- Executes on button press in connect.
function connect_Callback(hObject, eventdata, handles)
    guidata(hObject, handles); % Update handles structure

    % Check if a connection already exists
    if ~isempty(handles.connection) && isvalid(handles.connection)
        fclose(handles.connection);
    end

    % Specify your Bluetooth COM port
    bluetoothCOMPort = 'COM5';  

    % Create a Bluetooth connection
    handles.connection = bluetooth('HC-05', bluetoothCOMPort);

    % Check if the connection is valid
    if ~isempty(handles.connection) && isvalid(handles.connection)
        disp(['Bluetooth connection opened successfully on ', bluetoothCOMPort]);
    else
        disp(['Failed to create Bluetooth connection on ', bluetoothCOMPort]);
    end

    % Update handles structure
    guidata(hObject, handles);

% --- Executes on button press in disconnect.
function disconnect_Callback(hObject, eventdata, handles)
    % If a connection is open, close it
    if ~isempty(handles.connection) && isvalid(handles.connection)
        fclose(handles.connection);
        disp('Bluetooth connection closed.');
    else
        disp('No active Bluetooth connection.');
    end
    guidata(hObject, handles);

% --- Executes on button press in getdata.
function getdata_Callback(hObject, eventdata, handles)
    % If a connection exists, read the data from it
    if ~isempty(handles.connection) && isvalid(handles.connection)
        dataStr = fscanf(handles.connection); % Read string from connection
        if isempty(dataStr)
            disp('No data received from Arduino.');
            return;
        end

        disp(['Received data: ', dataStr]);

        data = strsplit(dataStr, ','); % Split the string into temperature and humidity

        if numel(data) >= 2 % Check that we have enough data
            % For each plot, gather the x and y data, append to the data arrays, and update the data in the plot
            for plotHandle = [handles.TempGraph, handles.HumGraph]
                xData = get(plotHandle, 'XData');
                yData = get(plotHandle, 'YData');

                xData(end+1) = xData(end) + 1; % Increment the time
                yData(end+1) = str2double(data{1}); % Append the new data point into the array
                set(plotHandle, 'XData', xData, 'YData', yData);

                data(1) = []; % Remove the first element from data
            end
            disp('Data plotted successfully.');
        else
            disp('Insufficient data received from Arduino.');
        end
    else
        disp('No active Bluetooth connection. Cannot get data.');
    end
    guidata(hObject, handles); % Update handles structure

[Sathvik]

Hi

The error message you have received suggests that the connection to the device already exists. Can you modify the 'connect_Callback' function as follows and check if the issue still persists?

...

function connect_Callback(hObject, eventdata, handles)
    guidata(hObject, handles); % Update handles structure
    % Check if a connection already exists
    if ~isempty(handles.connection) && isvalid(handles.connection)
        fclose(handles.connection);
        handles.connection=[]; % Modification made here
    end

...

Ensure that the workspace is empty before running.