This is an example of setting up an interrupt on an Arduino Uno.

Pin 2 (0) is the interrupt input pin.

Pin 12 - output
Pin 13 - output

This code toggles high/low on the two output pins when an interrupt is detected. When pin 12 is high, pin 13 is low and vice versa.

A delay was added in the interrupt code for testing purposes only and is not necessary.