using a timer in GUI

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

[Sean de Wolski]

What's the full error message?

[Daniel]

 now i tried:

handles.timer1 = timer('executionmode',fixedrate','period',0.005,'timerfcn',@NameOfFun);                
and:
function NameOfFun()
 do something
end

error: error while evaluating TimerFcn for timer 'timer-14' Too many input arguments

Answer 1

[Sean de Wolski]

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.

[Daniel]

Thanks!!! it seems i tried every posible combination except that. So 3 more questions:

1. Do i need to pass handles as well?
2. It seems that at the start it jumps immediately to the function and not wait for the period i set to be over, why is that?(after the first time it returns every period as i expect it)
3.How do i reset the timer? i.e. i want the timer to jump to the function, BUT if i reset it in another place before period is over, i want the period to reset and jump to the function only if a reset had not been made

[Daniel]

Update: so it worked, but now i try to call a call back function from the timer_function. The code in the function:

function timer_X(src,evt,handles)
   XXX_callback(hObject, eventdata, handles)
end

the error:

Error while evaluating TimerFcn for timer 'timer-22'
Undefined function or variable 'hObject'

so i tried

function timer_X(hObject,evt,handles)
     XXX_callback(hObject, eventdata, handles)
  end

no the error: Error while evaluating TimerFcn for timer 'timer-23' Undefined function or variable 'eventdata'

so :) i tried:

function timer_X(hObject,eventdata,handles)
   XXX_callback(hObject, eventdata, handles)
end

and now.... i got the error:

Error while evaluating TimerFcn for timer 'timer-24'
Not enough input arguments

any idea?

[Sean de Wolski]

For a delay after it starts, use the timer's 'StartDelay' property.

hObject is not defined in the timer callback. Typically, hObject is the handle to the calling object so if you want to call the callback for pushbutton1, you would call it as

function timercallback(thistimer,evt,handles)
pushbutton1_callback(handles.pushbutton1,eventdata,handles)

Explicitly creating "hObject".

[Sean de Wolski]

Out of curiosity, how complex is the user interface you're building?

[Daniel]

I cant seem to get it to work. Here is what i have:

In the starting func if have the following:
handles.timer1 = timer(...
      'ExecutionMode','FixedRate',...
      'period',2,...
      'StartDelay',2,...
      'TimerFcn',{@my_timer,handles});
end  %end of start fcn

function DATA_SAVE_Callback(hObject,eventdata,handles) 
   %some code
end

function my_timer(mytimer,evt,handles) %as you suggested
 DATA_SAVE_CallBack(handles.DATA_SAVE,eventdata,handles)
end
error:"error while evaluating TimerFCN...
undefind function or variable 'eventdata'"

I don't think my program is too complex. I have several buttons to send info request from an external system. I have text boxes to show the incoming info. I have a state machine to chk the incoming message is ok (HEADERS, CRC) and direct the info to the correct place. I have several edit boxes where the user can enter a parameter that will be written to the system (and immediately after i do a read to chk everything is ok)

and now i want to save data to a file. for that i want to send info request messages in a serial mode, i.e. ask for data 1, after i get it (this is where the timer kicks in as a WATCHDOG timer) i ask for data 2 and so on. so i basically need the timer to tell me: OK, X time has passed, no answer, resend request.

but i am pretty stuck with operating the timer

[Daniel]

UPDATE: I moved the handles.timer1 deceleration to the function where i set up the serial communication, immediately after i establish the communication. now it seems to work... I apparently dont fully understand where all these handles "live" and why it didn't work while defining it in the openingFCN

[Sean de Wolski]

This error

function my_timer(mytimer,evt,handles) %as you suggested
DATA_SAVE_CallBack(handles.DATA_SAVE,eventdata,handles)
end
error:"error while evaluating TimerFCN...
undefind function or variable 'eventdata'"

is happening because the variable is named evt not eventdata.

The handles are stored as part of the figure's data. in order to update them after appending timer1 you need to run:

guidata(handles.figure1,handles)

to update the state. This is what happens in the OpeningFcn.

If your user interface is not that complex, and you're on R2016a, then give app designer a try. It manages data in a much clearer, easier, and more modern way.

>> appdesigner

[Daniel]

Hi, Sorry for to late "bump". So everything was working fine. I used a timer as a watchdog timer, worked perfectly. Now i decided to restrict the timer to 3 operation only, i.e. send message request, if no answer, try 3 times( 3 timer periods) to resend request , if still no answer, ask for next message (message number 2). So i use stopfcn, and tasksto execute and now nothing works again.

function serial_com_Start
...code
handles.timer1 = timer(...
'taskstoexecute',3,...
'stopfcn'.{@param_request,hanles},...
'timerfcn',{@timerfunc,handles});
... code...
guidata(hObject,handles)
end

function timerfunc(~,~,handles)
fwrite(handles.serPIC,output1); %if no answer re send info
end

function param_request(~,~,handles)
fwrite(handles.serPIC,output2);
start(handles.timer1)
end

THE ERROR: error while evaluating StopFcn for timer 'timer-20' reference to non-existent field 'timer1'

from my understanding its the start timer i use in the last function. but how can i do it differently?