Programming and Data Types

Creating Timer Callback Functions

Four of the timer object properties specify callback functions that the timer object executes:

• ErrorFcn
• StartFcn
• StopFcn
• TimerFcn

As the value of these properties, you can specify:

• A text string containing MATLAB functions or an M-file name, e.g., 'disp(''Hello World!'')'
• A MATLAB function handle, e.g., @my_callback_fcn
• A cell array specifying an M-file and its arguments, e.g., {'my_callback_fcn',...} or {@my_callback_fcn,...}

When you set the value of these properties, you can specify arguments for the callback function using any of the following syntaxes.

Callback Function Syntax	Example
Function myfile	set(h, 'StartFcn', 'myfile')
Function myfile(obj, event)	set(h, 'StartFcn', @myfile)
Function myfile(obj, event, arg1, arg2)	set(h, 'StartFcn', {'myfile', 5, 6})
Function myfile(obj, event, arg1, arg2)	set(h, 'StartFcn', {@myfile, 5, 6})

The following diagram illustrates when the timer object executes the StartFcn, StopFcn, and TimerFcn. The ErrorFcn can occur at any time.

In this figure, the timer stops after two executions of the timer callback function (TimerFcn):

• t = timer('StartDelay',10,'TimerFcn','disp(''Hello World!'')', 
  'Period', 10,'TasksToExecute',2);
  
  
  

Timer Object Execution Modes

Character Arrays (Strings)