Problem with handles in GUI

Hi - I am having a problem with handles in guide. I have created a GUI to run some laboratory experiments and acquire data(maybe I should be using Simulink for this?).

In the gui I have created a timer object to schedule reading of the instruments. I have set up a instrument on opening the gui:

handles.controller1=visa('agilent','GPIB0::3::INSTR');

When the timer is triggered I would like to write a sequence of commands to the instrument through the callback function. Here is where the problem is as the visa object is not transferred through the handles when referenced, e.g.:

fwrite(handles.controller1, '63', 'uint8'); %UNL

On the other hand, if I don't try to write to the controller and just display the handles in the call back function to the command window the object is shown in the handles...??? [Using a script with a series of commands I am able to communicate with the instrument so I am confident that the code works].

Any assistance would be great!

Thanks

Answer 1

[Jan]

You have to provide the handles variable to the callback of the timer. E.g.:

set(TimerHandle, 'UserData', handles);

And then inside the callback:

function TimerCallback(ObjH, EventData)
handles = get(ObjH, 'UserData');
...

Another idea would to append handles as third input:

set(TimerH, 'TimerFcn', {@TimerCallback, handles});

Then the callback catches this as:

function TimerCallback(ObjH, EventData, handles)