Error while evaluating TimerFcn for timer 'timer-1' Reference to non-existent field 'fileID'. How to pass fileID to timer? Thanks My code:

function varargout = untitled1(varargin)
% % % % % 
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @keithley_OpeningFcn, ...
                   'gui_OutputFcn',  @keithley_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
% End initialization code - DO NOT EDIT

function keithley_OpeningFcn(hObject, eventdata, handles, varargin)

handles.output = hObject;
delete(instrfindall);
set(findobj('Type','uicontrol'), 'BusyAction','cancel', 'Interruptible','off');
%------------------------------------------------------------------------------%
g = instrfind('Type', 'gpib', 'BoardIndex', 0, 'PrimaryAddress', 10, 'Tag', '');
if isempty(g)
    g = gpib('ni', 0, 10);
else
    fclose(g);
    delete(g);
    clear obj1;
    g = gpib('ni', 0, 10);
end
g.EOSMode = 'read&write';
g.Timeout = 1;
handles.g = g;
%------------------------------------------------------------------------------%
handles.timer = timer(...
    'ExecutionMode', 'fixedRate', ...       % Run timer repeatedly
    'Period', 1, ...                        % Initial period is 1 sec.
    'TimerFcn', {@readdata,handles}); % Specify callback function
% Update handles structure
guidata(hObject, handles);

function varargout = keithley_OutputFcn(hObject, eventdata, handles) 
varargout{1} = handles.output;

function measure_button_Callback(hObject, eventdata, handles)
    fopen(handles.g);
    fprintf(handles.g,':OUTP ON'); %  output on
    fprintf(handles.g,':INIT'); % start
    fileID = fopen(handles.fullfile,'a'); %handle to file
    handles.fileID = fileID;
    readdata(hObject,eventdata,handles);
    start(handles.timer)  

guidata(hObject,handles)

function readdata(hObject,eventdata,handles)
          fprintf(handles.g,':READ?'); % trigger and aquire reading
          read = fscanf(handles.g);
          date_string = datestr(now,'dd-mmm-yyyy HH:MM:SS.FFF');
          fprintf(handles.fileID,'%s;%s',date_string,read);
          guidata(hObject,handles)

function save_button_Callback(hObject, eventdata, handles)
[filename, pathname] = uiputfile({'*.txt'},'Save as');
if isequal(filename,0) || isequal(pathname,0)
   disp('User selected Cancel')
else
   disp(['User selected ',fullfile(pathname,filename)])
handles.fullfile = fullfile(pathname,filename);
handles.filename = filename;
end
guidata(hObject,handles)

function Exit_pushbutton_Callback(hObject, eventdata, handles)
delete(handles.timer)
close all;

function stop_measurements_button_Callback(hObject, eventdata, handles)
stop(handles.timer);
fclose(handles.fileID);
fprintf(handles.g,':OUTP OFF'); % output off
fclose(handles.g);    
guidata(hObject,handles);

Answer 1

[Steven Lord]

 handles.timer = timer(...
    'ExecutionMode', 'fixedRate', ...       % Run timer repeatedly
    'Period', 1, ...                        % Initial period is 1 sec.
    'TimerFcn', {@readdata,handles}); % Specify callback function

This probably won't do what you want. This will pass a copy of the handles structure as it exists when this line of code is executed into your readdata function. Any changes to the handles structure in this function, or to the "master copy" of the handles structure (like the fileID field you add to the handles structure inside measure_button_Callback), will NOT be recognized.

In order to allow the readdata function to access the most up-to-date handles structure, instead of passing in the handles structure pass in something that's not going to change but from which you can retrieve the handles structure, like the handle to the main GUI figure (which you can use with GUIDATA inside the TimerFcn.)

[Lukasz Wozniak]

Thank you for your answer. I tried to follow your suggestions, I do not know if I did it correctly. However, now it gives me an error:" H must be the handle to a figure or figure descendent."

Any ideas?

 function varargout = untitled1(varargin)
  % % % % % 
  gui_Singleton = 1;
  gui_State = struct('gui_Name',       mfilename, ...
                     'gui_Singleton',  gui_Singleton, ...
                     'gui_OpeningFcn', @keithley_OpeningFcn, ...
                     'gui_OutputFcn',  @keithley_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
% End initialization code - DO NOT EDIT

function keithley_OpeningFcn(hObject, eventdata, handles, varargin)

handles.output = hObject;
   

delete(instrfindall);
set(findobj('Type','uicontrol'), 'BusyAction','cancel', 'Interruptible','off');
%------------------------------------------------------------------------------%
g = instrfind('Type', 'gpib', 'BoardIndex', 0, 'PrimaryAddress', 10, 'Tag', '');
if isempty(g)
    g = gpib('ni', 0, 10);
else
    fclose(g);
    delete(g);
    clear obj1;
    g = gpib('ni', 0, 10);
end
g.EOSMode = 'read&write';
g.Timeout = 1;
handles.g = g;
%------------------------------------------------------------------------------%
handles.timer = timer(...
    'ExecutionMode', 'fixedRate', ...       % Run timer repeatedly
    'Period', 1, ...                        % Initial period is 1 sec.
    'TimerFcn', {@readdata,handles}); % Specify callback function

setappdata(handles.figure1,'fileI',0); 
% Update handles structure
guidata(hObject, handles);
  
   

function varargout = keithley_OutputFcn(hObject, eventdata, handles) 
varargout{1} = handles.output;

function measure_button_Callback(hObject, eventdata, handles)
    fopen(handles.g);
    fprintf(handles.g,':OUTP ON'); 
    fprintf(handles.g,':INIT'); % start measurements
    fileID = fopen(handles.fullfile,'a'); 
    setappdata(handles.figure1,'fileI',fileID); 
    handles.fileID = fileID;
    start(handles.timer)  
  

guidata(hObject,handles)

function readdata(hObject,eventdata,handles)     
          fileID = getappdata(handles.figure1,'fileI');
          fprintf(handles.g,':READ?'); 
          read = fscanf(handles.g);
          date_string = datestr(now,'dd-mmm-yyyy HH:MM:SS.FFF');
          fprintf(fileID,'%s;%s',date_string,read);
          guidata(hObject,handles)

function save_button_Callback(hObject, eventdata, handles)
[filename, pathname] = uiputfile({'*.txt'},'Save as');
if isequal(filename,0) || isequal(pathname,0)
   disp('User selected Cancel')
else
   disp(['User selected ',fullfile(pathname,filename)])
handles.fullfile = fullfile(pathname,filename);
handles.filename = filename;

end
guidata(hObject,handles)

function Exit_pushbutton_Callback(hObject, eventdata, handles)

delete(handles.timer)
close all;

function stop_measurements_button_Callback(hObject, eventdata, handles)

stop(handles.timer);
    fclose(handles.fileID);
    fprintf(handles.g,':OUTP OFF'); % output off
    fclose(handles.g);    
guidata(hObject,handles);

[Lukasz Wozniak]

And when I change code like this:

handles.timer = timer(...
    'ExecutionMode', 'fixedRate', ...       % Run timer repeatedly
    'Period', 1, ...                        % Initial period is 1 sec.
    'TimerFcn', {@readdata,gcf}); % Specify callback function

I get :" Attempt to reference field of non-structure array"

[Walter Roberson]

In measure_button_Callback after you assign to handles.fileID you failed to use guidata() to update the master copy of handles. The master copy of handles will not have a fileID field available to be used in stop_measurements_button_Callback .

You should be consistent about whether you are storing the information in handles or by using setappdata / getappdata; you are confusing yourself by trying to mix the two.

[Lukasz Wozniak]

Steven wrote : "pass in something that's not going to change but from which you can retrieve the handles structure, like the handle to the main GUI figure (which you can use with GUIDATA inside the TimerFcn.)". So how to pass something in a handle to the main GUI figure? Can I get an example code?

[Walter Roberson]

handles.timer = timer(... 'ExecutionMode', 'fixedRate', ... % Run timer repeatedly 'Period', 1, ... % Initial period is 1 sec. 'TimerFcn', {@readdata,gcbf}); % Specify callback function

function readdata(hObject,eventdata,fig)
  handles = guidata(fig);
  ...

[Lukasz Wozniak]

Dear Walter Roberson I did as You suggested and now I have an error: "H must be the handle to a figure or figure descendent."

[Steven Lord]

Don't use GCBF here unless you're creating the timer inside one of the callback functions of a component in your GUI. Get the handle to the GUI you want to access in your timer and use that handle, whatever it's called, to set your TimerFcn.

function figureColorChangeExample
qwerty = figure;

% qwerty contains the figure handle so I use it to construct t
t = timer('ExecutionMode', 'fixedRate', ...
   'Period', 1, ...
   'TimerFcn', {@changeColor,qwerty});
start(t)
pause(10)
stop(t)
close(qwerty)

function changeColor(hObject,eventdata,handleToFigure)
  set(handleToFigure, 'Color', rand(1, 3));

When you execute this function it should bring up a figure, change its color for ten seconds, then close the figure.

Answer 2

[Lukasz Wozniak]

For clarity I am pasting the whole code, with Your suggestions. And the whole error messege when I tried to press measure button:

"Error using guidata (line 89) H must be the handle to a figure or figure descendent.

Error in untitled1>readdata (line 71) handles = guidata(fig);

Error in untitled1>measure_button_Callback (line 63) readdata(hObject,eventdata,handles);

Error in gui_mainfcn (line 96) feval(varargin{:});

Error in untitled1 (line 17) gui_mainfcn(gui_State, varargin{:});

Error in @(hObject,eventdata)untitled1('measure_button_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback"

function varargout = untitled1(varargin)
  % % % % % 
  gui_Singleton = 1;
  gui_State = struct('gui_Name',       mfilename, ...
                     'gui_Singleton',  gui_Singleton, ...
                     'gui_OpeningFcn', @keithley_OpeningFcn, ...
                     'gui_OutputFcn',  @keithley_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
% End initialization code - DO NOT EDIT

function keithley_OpeningFcn(hObject, eventdata, handles, varargin)

handles.output = hObject;
   

delete(instrfindall);
set(findobj('Type','uicontrol'), 'BusyAction','cancel', 'Interruptible','off');
%----------------------------------------------------------------------------%
g = instrfind('Type', 'gpib', 'BoardIndex', 0, 'PrimaryAddress', 10, 'Tag', '');
if isempty(g)
    g = gpib('ni', 0, 10);
else
    fclose(g);
    delete(g);
    clear obj1;
    g = gpib('ni', 0, 10);
end
g.EOSMode = 'read&write';
g.Timeout = 1;
handles.g = g;
gcbf = gcf;
%------------------------------------------------------------------------------%
handles.timer = timer(...
    'ExecutionMode', 'fixedRate', ...       % Run timer repeatedly
    'Period', 1, ...                        % Initial period is 1 sec.
    'TimerFcn', {@readdata,gcbf}); % Specify callback function
% Update handles structure
guidata(hObject, handles);
  
   

function varargout = keithley_OutputFcn(hObject, eventdata, handles) 
varargout{1} = handles.output;

function measure_button_Callback(hObject, eventdata, handles)
    fopen(handles.g);
    fprintf(handles.g,':OUTP ON'); % 
    fprintf(handles.g,':INIT'); % start measurements
    fileID = fopen(handles.fullfile,'a'); 
    handles.fileID = fileID;
    readdata(hObject,eventdata,handles);
      
    start(handles.timer)  
  

guidata(hObject,handles)

function readdata(hObject,eventdata,fig)     
          handles = guidata(fig);
          fprintf(handles.g,':READ?'); % trigger and aquire reading
          read = fscanf(handles.g);
          date_string = datestr(now,'dd-mmm-yyyy HH:MM:SS.FFF');
          fprintf(handles.fileID,'%s;%s',date_string,read);
          guidata(hObject,handles)

function save_button_Callback(hObject, eventdata, handles)
[filename, pathname] = uiputfile({'*.txt'},'Save as');
if isequal(filename,0) || isequal(pathname,0)
   disp('User selected Cancel')
else
   disp(['User selected ',fullfile(pathname,filename)])
handles.fullfile = fullfile(pathname,filename);
handles.filename = filename;

end
guidata(hObject,handles)

function Exit_pushbutton_Callback(hObject, eventdata, handles)

delete(handles.timer)
close all;

function stop_measurements_button_Callback(hObject, eventdata, handles)

stop(handles.timer);
    fclose(handles.fileID);
    fprintf(handles.g,':OUTP OFF'); % output off
    fclose(handles.g);    
guidata(hObject,handles);

Answer 3

[Lukasz Wozniak]

So, my problem is unsolvable?