MATLAB: Using a timer in GUI

guitimer

Hi, I have a GUI to manage UART communication. I want to use a timer as follows: if i haven't got the answer for what i requested, in 4ms time ,then re-send the request (for example).

I tried several timer configuration and for each i get an error message:"error while evaluating timerfcn for timer 'timer-x' , where x is keep changing.

i tried: in openingFcn:

handles.timer1 - timer('executionmode',fixedrate','period',0.005,'timerfcn',@(src,event)NameOfFunc(src,event,handles));

in the desierd callback :

start(handles.timer1)

in the function

function NameOfFunc(src,event,handles)
    DO SOMETHING
end

i get error (this time) error while evaluating timerfcn for timer 'timer-6' i also tried defining the timer as a global parameter

Best Answer

function NameOfFun()
do something
end

Needs to take in the two inputs that come by default, src, evt.

function NameOfFun(src,evt)
do something
end

If you also want to pass in handles, like in your original, it needs to take in three inputs.

Related Solutions

MATLAB: How to avoid calling Arduino all the times in a timer function

Elena - store the Arduino object in the handles structure so that you don't have to re-initialize each time. I would do this for the timer objet too so that you have the means to stop the timer from (say) a stop callback button.

For example,

 function CmdStart_Callback(hObject, eventdata, handles)
 set(handles.CmdStart, 'Enable', 'Off');
 disp('Start Timer');
 handles.Timer1= timer('name','Period');
 handles.Timer1.ExecutionMode = 'FixedSpacing';
 handles.Timer1.Period = txtTime;
 handles.Timer1.TimerFcn = {@SoilHumidityforGUI, hObject}; 
 handles.Timer1.ErrorFcn = @ErrorFcn;
 handles.arduinoObj = arduino ('com3', 'mega2560');
 % save the updated handles object
 guidata(hObject, handles);
 start(handles.Timer1);

When we call guidata, the handles structure is updated with the timer and Arduino objects. (Note how I've removed the global declaration. This is no longer needed for Timer1 but still may be for your txtTime although you may be able to use handles for this too.)

Also, see how the timer callback has been declared

 handles.Timer1.TimerFcn = {@SoilHumidityforGUI, hObject};

We are passing another parameter to this function (besides the default ones) which is the handle to pushbutton. The idea is that we will use this to retrieve the handles structure from within the timer as

 function SoilHumidityforGUI (~,~,hObject)
 handles = guidata(hObject);
 if isfield(handles,'arduinoObj')
     H= (readVoltage (handles.arduinoObj, 'A0'));
 else
     fprintf('Error - cannot find arduinoObj in handles structure!!\n');
 end

I haven't tested the above, so try it out and see what happens!

MATLAB: How to make a timer execute an internal function in gui

When you use a string to designate a function in a callback, then the string is eval()'d in a context equivalent to the base workspace, outside of any hierarchy. Only functions that are built-in or which have .m on the path can be accessed that way.

You should switch to using a function handle. Also, you need to make an adjustment for the fact that you are not expecting the standard parameters in your callback

handles.t = timer('BusyMode', 'queue', 'ExecutionMode',...
'fixedRate', 'Period', 4.0);
set(handles.t, 'TimerFcn', @(hObject, event) funkcija(event, handles));

Note that the handles variable that will be passed in to the callback will contain exactly whatever the handles structure contained at the time the anonymous function was created. The reason for splitting the assignment of handles.t and the setting of TimerFcn is that splitting it allows the timer handle itself to be recorded in the handles structure before that version of the structure is "frozen" for the purposes of the anonymous function.

If you want the current version of the handles object to be passed in to the function at the time the timer is fired, then the easiest route is to pass in information that allows you to figure out where the handle structure is. For example, you could use

handles.t = timer('BusyMode', 'queue', 'ExecutionMode',...
'fixedRate', 'Period', 4.0, 'TimerFcn', @funkcija);

with

 function funkcija(hObject, EventData)
   handles = guidata(hObject);
   a = 1;

Best Answer

Related Solutions

MATLAB: How to avoid calling Arduino all the times in a timer function

MATLAB: How to make a timer execute an internal function in gui

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