Passing a listener from GUIDE function to a function outside of GUIDE?

Hello everyone - I hope this is a simple question, but I've been struggling for days to get this to work. I have made a GUI via GUIDE that acquires data in the background. However, I'm having trouble getting the function I call in addlistener to have the handle for the listener used. I've been able to get it working in a script by itself as an anonymous function, and I have been able to write a script that calls it and it works well. However, once I try to implement it into the GUI it does not work anymore. I think it may be an issue with updating handles and/or calling the handles from the GUI to the current m file function. Below is are my two functions, any help? Running R2014b.

% --- Executes on button press in Toggle.
function Toggle_Callback(hObject, eventdata, handles)
% hObject    handle to Toggle (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
if get(handles.Toggle,'Value') == 1;

if exist('TempDataFile.txt', 'file') == 2
    delete('TempDataFile.txt');
end
openDAQ = daqfind;                
for n = 1 : length(openDAQ)              
    delete(openDAQ(n));                
end  
newDAQ=daq.createSession('ni');
newDAQ.addAnalogInputChannel('Dev1','ai0','Voltage');  
newDAQ.addAnalogInputChannel('Dev1','ai1','Voltage');
newDAQ.IsContinuous = true;
newDAQ.Rate=10;

% newDAQ.DurationInSeconds=1;     

lh = addlistener(newDAQ, 'DataAvailable', @plotData);
guidata(hObject, handles); 
plotData(lh);    

newDAQ.startBackground();

else 
    stop(newDAQ);
    newDAQ.IsContiniuous = false;

end

And the function called in lh (which is plotData.m):

function  plotData(newDAQ,DataAvailable, lh)
handles = guidata(gcbo);
%get(handles.lh, 'DataAvailable');
    Time = [];
    Data1 = [];
    Data2 = [];
    axes(handles.axes1); 
    plot(DataAvailable.TimeStamps, DataAvailable.Data(:,1), 'xb');
    plot(DataAvailable.TimeStamps, DataAvailable.Data(:,2), 'og');

      Time(:,1) = DataAvailable.TimeStamps;
      Data1(:,1) = DataAvailable.Data(:,1);
      Data2(:,1) = DataAvailable.Data(:,2);

      TempData = [];
      TempData(:,1) = Time;
      TempData(:,2) = Data1;
      TempData(:,3) = Data2;

      dlmwrite('TempDataFile.txt',TempData, '-append');

end

Effectively, I'm trying to use the listener lh to obtain the data in a different function in GUIDE from where I initialized it and it still isn't working.

Thank you for your help in advance!

Answer 1

[Geoff Hayes]

Eric - save lh to the handles structure as

 function Toggle_Callback(hObject, eventdata, handles)

 % your code

 % create listener
 handles.lh = addlistener(newDAQ, 'DataAvailable', @plotData);

 % save updated handles structure
 guidata(hObject, handles);

Now, in every other callback that has handles as an input parameter, just access lh as

 handles.lh

In your case though, you seem to be passing lh into plotData. Why is that? In fact, why does your function need to know about the listener? If you want to pass a third parameter in to the plotData function, then you would need to do

 lh = addlistener(newDAQ, 'DataAvailable', {@plotData,handles.figure1});

where I'm assuming that figure1 is the name of your GUI. In the plotData function you would then do

 function  plotData(newDAQ,DataAvailable, guiHandle)
 handles = guidata(guiHandle);
 lh = [];
 if isfield(handles,'lh')
     lh = handles.lh;
 end

 % etc.

But...why does plotData need to know about lh?

[Eric]

Hi Geoff - thanks for your response. I want plotData to know about lh so that I can operate on lh. I want to obtain continuous data from the daq card and operate on it. I'm obtaining data from to analog inputs and want to plot them at a user defined rate in plotData. I have another function, opData that operates on the data by summing or subtracting the two channels, while plotting continuously until the user toggles the button "off".

How do know what the guiHandle is? I'm sorry for the questions - I'm new to using listeners and passing handles, etc.

Thanks in advance for all your help.

Eric

[Geoff Hayes]

Hi Eric - guiHandle is the extra parameter that you pass in to the callback at

lh = addlistener(newDAQ, 'DataAvailable', {@plotData,handles.figure1});

The handles.figure1 (which may be named differently for your GUI) is the handle to the GUI. I still don't understand how you might go about using this listener in any of your other functions or callbacks though...