creating a timer in GUI

Hi I'm using GUI for do a spectrum analyzer interface. My problem is when I create a timer and call my function, appears a warning, something like that:

"the "handles" estructure is no defined or recognized"

thi is a part of my code:

% --- Executes on button press in pushbutton4.
function pushbutton4_Callback(hObject, eventdata, handles)
obj1 = instrfind('Type', 'gpib', 'BoardIndex', 0, 'PrimaryAddress', 18, 'Tag', '');
if isempty(obj1)
    obj1 = gpib('ni', 0, 18);
else
    fclose(obj1);
    delete(obj1);
    clear obj1;
    obj1 = gpib('ni', 0, 18);
end
% Configure instrument object, obj1.
set(obj1, 'InputBufferSize', 10000);
set(obj1, 'OutputBufferSize', 10000);
% Connect to instrument object, obj1.
set(obj1,'Timeout',5);
fopen(obj1);
Nombre = query(obj1, '*IDN?');
set(handles.text1,'String',Nombre);

fprintf(obj1,':FORM:BORD SWAP');
fprintf(obj1,':FORM:DATA REAL,32');
% Get the nr of trace points
nr_points = str2double(query(obj1,':SWE:POIN?'));
% Get the reference level
ref_lev = str2num(query(obj1,':DISP:WIND:TRAC:Y:RLEV?'));
% Put the instrument in continuos mode
fprintf(obj1,':INIT:CONT ON');
% Create and bring to front fi gure number 1
%figure(1)
% Create a plot handle, ph, and draw a line at the refl evel
handles.axes1=(1:nr_points);
ph = plot(handles.axes1,ref_lev*ones(1,nr_points));
% Adjust the x limits to the nr of points
% and the y limits for 100 dB of dynamic range
xlim([1 nr_points])
ylim([ref_lev-100 ref_lev])
% Activate the grid
grid on
t =timer('timerfcn',@graficar,'Period',0.1);  //THIS IS MY TIMER
handles.varobj1=obj1;
handles.varph=ph;
start(t);
guidata(hObject,handles);
% hObject    handle to pushbutton4 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

    function graficar(hObject, eventdata, handles) //THIS IS MYFUNCTION
    obj1=handles.varobj1; //THE WARNING REFERS TO THIS 
    ph=handles.varph;     //LINE OF CODE
    fprintf(obj1,':TRAC? TRACE1');
    data = binblockread(obj1,'float32');
    fscanf(obj1); %removes the terminator character
    % Change the plot line data (fast update method)
    set(ph,'Ydata',data);
    % fl ushes the plot event queue
    drawnow
    guidata(hObject,handles);

Answer 1

[Walter Roberson]

t  = timer('timerfcn', {@graficar, gcf},'Period',0.1);

and

   function graficar(hObject, eventdata, fignum)
      handles = guidata(fignum);

[Jose]

thanks

[Luke Somers]

Where did 'gcf' come from? Does it even matter what you put there? How do you know that it's going to be a figure or an element of one? Is it a global?

[Walter Roberson]

Better would probably have been

t  = timer('timerfcn', {@graficar, hObject}, 'Period',0.1);

What needs to go in that location is any graphic handle belonging to the same figure that is the GUI.

Based upon the style and variable names, we can tell the framework was generated by GUIDE, and for GUIDE, the first parameter of the function, hObject, is always the same figure as the handles are attached to. In truth, GUIDE has a bug or limitation in this matter, that it can only properly manage the handles structure (third parameter) for callbacks for graphics objects in the same figure as the GUI.