Matlab GUI Error = "H must be the handle to a figure or figure descendent."

Hello, I get this error when I run my program. I'm thinking it's about external function which is serialEventHandler but I am not sure about that. Also when I delete guidata(hObject,handles) under the serialEventHandler, that code doesn't work well. Here is my code;

function start_communication_Callback(hObject, eventdata, handles)
if ~isempty(instrfind)
   fclose(instrfind);
   delete(instrfind);
end
handles.time_axes = zeros(1,100);
handles.receiving_data_yaw_axes = zeros(1,100);
handles.receiving_counter = 1;
handles.axis_counter = 0;
my_serial_port = serial(handles.selected_port,'BAUD', str2double(handles.selected_baudrate));
handles.my_serial_port = my_serial_port;
set(handles.my_serial_port, 'BytesAvailableFcnMode', 'byte');
set(handles.my_serial_port, 'BytesAvailableFcnCount', 6);
handles.my_serial_port.BytesAvailableFcn = {@serialEventHandler,handles};
fopen(my_serial_port);
set(findall(handles.communication_group, '-property', 'enable'),'Enable','off')
tic;
guidata(hObject, handles);  
      
function serialEventHandler(hObject, eventdata, handles, bytesToRead)
receiving_data = fread(handles.my_serial_port,6);
handles.receiving_counter = handles.receiving_counter + 1;
disp(handles.receiving_counter);

set(handles.timer_example_edit,'string',num2str(toc));

handles.receiving_data_yaw_axes(1,handles.receiving_counter) = receiving_data(1);
handles.time_axes(1,handles.receiving_counter) = toc;

if handles.receiving_counter >= 100
    handles.axis_counter = handles.receiving_counter - 100;
end

axes(handles.real_time_plot_axes);
handles.real_time_plot_axes.XLim = [handles.axis_counter handles.axis_counter+100];
handles.real_time_plot_axes.YLim = [0 100];
plot(handles.real_time_plot_axes,handles.time_axes,handles.receiving_data_yaw_axes);
drawnow;

set(handles.receive_yaw_edit,'string',num2str(receiving_data(1)));
set(handles.receive_pitch_edit,'string',num2str(receiving_data(2)));
set(handles.receive_roll_edit,'string',num2str(receiving_data(3)));
guidata(hObject, handles); 

Answer 1

[Geoff Hayes]

Burak - probably too late to help but in

function serialEventHandler(hObject, eventdata, handles, bytesToRead)

the hObject parameter is (probably) the handle to the serial object. That is why, when you call (from this function)

guidata(hObject, handles); 

you get the "H must be the handle to a figure or figure descendent" error. When assigning the callback, you can pass the handle to the figure/GUI instead

handles.my_serial_port.BytesAvailableFcn = {@serialEventHandler,handles.figure1};

using the field from handles that corresponds to the GUI (I'm assuming it is figure1 in the above code). Your callback could then become

function serialEventHandler(hObject, eventdata, bytesToRead, hGui)
handles = guidata(hGui);
% etc.

You will want to confirm that the handle to the figure (hGui) is the last parameter passed into this callback. I'm assuming it is but that assumption could be wrong.