External Interfaces/API

Events and Callbacks

You can enhance the power and flexibility of your serial port application by using events. An event occurs after a condition is met and might result in one or more callbacks.

While the serial port object is connected to the device, you can use events to display a message, display data, analyze data, and so on. Callbacks are controlled through callback properties and callback functions. All event types have an associated callback property. Callback functions are M-file functions that you construct to suit your specific application needs.

You execute a callback when a particular event occurs by specifying the name of the M-file callback function as the value for the associated callback property.

Example: Introduction to Events and Callbacks

This example uses the M-file callback function instrcallback to display a message to the command line when a bytes-available event occurs. The event is generated when the terminator is read.

• s = serial('COM1');
  fopen(s)
  s.BytesAvailableFcnMode = 'terminator';
  s.BytesAvailableFcn = @instrcallback;
  fprintf(s,'*IDN?')
  out = fscanf(s);
  

The resulting display from instrcallback is shown below.

• BytesAvailable event occurred at 17:01:29 for the object: 
  Serial-COM1.
  

End the serial port session.

• fclose(s)
  delete(s)
  clear s
  

You can use the type command to display instrcallback at the command line.

Example: Reading Binary Data

Event Types and Callback Properties