How can I create an analog output?

Hello! This is my first article. Sorry if I have done any mistakes!

I try to create a analog output in MATLAB to control my Data Translation DT9834.

I need an output of 7 Volt. I will use a GUI with a pushbutton to start the signal. After 5 seconds the signal should be again 0 Volt.But there are any mistakes in my code. Maybe you can help me!

function analog_output_OpeningFcn(hObject, eventdata, handles, varargin)

handles.output = hObject;

global ao;

ao = analogoutput('dtol', 0);

addchannel(ao, 0);

addchannel(ao, 1);

set(ao, 'TriggerType', 'Immediate');

putsample(ao, [0 0]);

guidata(hObject, handles);
----------------------------------------------------------
function pushbutton1_Callback(hObject, eventdata, handles)
global ao;
putsample(ao, [7 7]);
start(ao);
wait(ao,5);

putsample(ao,[0 0]);

When I start the button, it appears this error:

Error using daq.analogoutput_dtol_1_31/start
Data must be queued using PUTDATA before starting.

Error in daqdevice/start (line 62)
start( daqgetfield(obj,'uddobject') );

Error in analog_output>pushbutton1_Callback (line 102)
start(ao);

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

Error in analog_output (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in
@(hObject,eventdata)analog_output('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback

I hope you can help me. Best regards!

Domi