Matlab GUI: Showing data from COM port in listbox without using any push button

I Want to display, in listbox, the data received in COM port. I can show the incoming data in listbox using push button. The data is showing exactly as long as I use push button, but after removing the push button and only using listbox [putting code in listbox's callback] nothing is showing. How can I use listbox to execute the code and shows what it is getting in COM port?

Code::

 function listbox1_Callback(hObject, eventdata, handles)

   s = serial ('COM6');   % the communication port 
   fopen(s);   %open the serial port
   scanText = fscanf(s);
   data = scanText;
   set(handles.listbox1,'String',...
         [data]);
   fclose(s);

Answer 1

[dpb]

Because there is no event for the listbox w/o a user intervention -- so the callback function will never be called.

You need to create a serial port event callback -- see documentation under "Events and Callbacks" link under the Serial Port Devices section. It's under Data and File Management chapter.

Answer 2

[Roberto]

The callback function of a listbox is executed when you select an element of the list, what I think you might want is to read from device automatically, to achieve this you can use the 'Create function' that is executed when the object is created:

function listbox1_Create_Fcn(hObject, eventdata, handles)
 s = serial ('COM6');   % the communication port 
 fopen(s);   %open the serial port
 scanText = fscanf(s);
 data = scanText;
 set(handles.listbox1,'String',...
       [data]);
 fclose(s);