[Thor_x86], aka [Eric], built an Arduino sketch that does just that — and he threw in the ability to send (or receive) serial messages, too. This is a neat idea — kind of a simplified Bus Pirate.

The code initializes an Arduino object, specifies the digital pin connected to the LED, and toggles its state in a loop. As shown in the MATLAB code, the LED is wired to digital pin 13 of the Arduino ...