MATLAB Answers


Problems updating variable on the callback of a timer

Asked by Ángel González on 19 Sep 2018
Latest activity Commented on by Christopher Wallace on 20 Sep 2018
Hi there! I'm trying to get a while-loop to exit depending on two variables; one of them is changed when a time is passed (using a timer). The other one is changed inside the while loop after a condition. All this while loop is also inside a for a loop.
Here is a draft of my code:
for i=i:N %%N defined previously
% Some operations
x = false;
timer_ event = false;
timer_1 = timer('StartDelay', time_limit, 'TimerFcn', 'timer_event = true');
while((x == false) && (timer_event == false))
% get samples
x = true;
The question here is that the while-loop only breaks when the x variable changes the value, but nothing happens when the timer callback changes the value of the timer_event variable.
Thank you so much!


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1 Answer

Answer by Christopher Wallace on 19 Sep 2018

Use the 'UserData' property of the timer to access data set within the timer function.
Look at the function I've attached to create a timer that modifies the UserData every period.
After running the function if you were to start the timer and repeatedly query the UserData you'll see it changing from true to false.
t = createTimer;
get(t, 'UserData')
>> get(t, 'UserData')
ans =
timer_event: 0
>> get(t, 'UserData')
ans =
timer_event: 1


I will take a look at that, but I have been trying different things on my code. The StartDelay property of the timer depends on a value introduced in GUI. When I use a constant StartDelay, everything works fine...but when I try to use a StartDelay introduced via GUI, the timer goes wrong.
If you upload your code I can take a look.

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