MATLAB: Stopping a Timer via another function

stoptimerwait

Hello.

Is there a way to stop a timer from another function whilst it is running. Im not sure what to pass to the other function:

This is my timer and wait part

T = timer('TimerFcn',@(~,~)disp('Fired.'),'StartDelay',10);
start(T)
wait(T)
delete(T)

I want to have a stop button which will allow me to stop if the wait hasn't finished, but not sure how to pass the timer object to that function to then apply

stop(T)

Best Answer

Jason - since you have a stop button, then you must be using a GUI which has (perhaps?) been created with GUIDE. If that is the case, then just save T to the handles structure so that when the stop button is pressed, it can stop the timer.

Suppose we have a simple GUI with two buttons - start and stop. The callback for the former starts the timer as

function start_Callback(hObject, eventdata, handles)
 handles.myTimer = timer('Name','MyTimer',               ...
                         'Period',1.0,                   ... 
                         'StartDelay',1,                 ... 
                         'TasksToExecute',30,            ... 
                         'ExecutionMode','fixedSpacing', ...
                         'TimerFcn',@(~,~)disp('Fired.')); 
  guidata(hObject,handles);
start(handles.myTimer);
wait(handles.myTimer);
fprintf('timer has stopped');
delete(handles.myTimer);

In the above, we create a timer that fires every one second for 30 times (so 30 seconds). If we launch the GUI and press the start button, we see Fired displayed 30 times in the console before the timer has stopped message is written.

Now suppose our stop callback is

 function stop_Callback(hObject, eventdata, handles)
 if isfield(handles,'myTimer')
     stop(handles.myTimer);
 end

Again, we launch the GUI and press the start button and observe the messages written to the console. But now we press the stop button before the 30 seconds is up and we observe that the timer has stopped message appears within a second.

Try the above and see what happens!

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MATLAB: Displaying Timer Function in Graph

sufyan - suppose that your timer starts when you press the start button in your GUI. The pushbutton callback would look something like

 function start_Callback(hObject, eventdata, handles)
 handles.timer = timer('Name','MyTimer',               ...
                       'Period',1.0,                   ... 
                       'StartDelay',0,                 ... 
                       'TasksToExecute',inf,           ... 
                       'ExecutionMode','fixedSpacing', ...
                       'TimerFcn',{@timerCallback,handles.figure1}); 
 guidata(hObject,handles);
 start(handles.timer);

The above timer will fire (roughly) every second. Note how we pass the GUI figure handle as an input to the timerCallback function. This is necessary so that we can access the handles structure (from there) to (potentially) update the axes with new data. The callback can be defined as

 function [] = timerCallback(~,~,guiHandle)
 if ~isempty(guiHandle)
      % get the handles
      handles = guidata(guiHandle);
      if ~isempty(handles)
          % use EEG handles.data (?) to update the axes
          % if new data, then update the axes
      end
  end

In the above, we get the handles structure using guihandles so that we can get the current set of data in the axes control. In your stop button callback, you would then stop the timer

 function stop_Callback(hObject, eventdata, handles)
 if isfield(handles, 'timer')
     stop(handles.timer);
 end

MATLAB: I have a script that I run via a timer every 30 minutes — how to run this in background

Robert - try creating a function that you can call from the command line. It will instantiate a timer and then periodically (whenever the timer callback fires) will do some work. For example, in a file named timerInBackground.m you could have

function [myTimer] = timerInBackground
myTimer = timer('Name','MyTimer',               ...
                'Period',30*60,                 ... 
                'StartDelay',0,                 ... 
                'TasksToExecute',inf,           ... 
                'ExecutionMode','fixedSpacing', ...
                'TimerFcn',@myTimerCallback); 
start(myTimer);
function myTimerCallback(hObject, eventdata)    
fprintf('hello!\n');

Then call this function from your command window as

 myTimer = timerInBackground;

Then every 30 minutes (30*60 seconds) the timer callback will fire and (in this case) print a hello! message to the console window. In the meantime, you can continue with other MATLAB tasks.

Best Answer

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MATLAB: Displaying Timer Function in Graph

MATLAB: I have a script that I run via a timer every 30 minutes — how to run this in background

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