With this handy 7 Pin Mini-DIN Connector you can now jack into the hackport on your iRobot and control it with an Arduino or some other favorite microcontroller that has a 5V TTL UART! You can also power your project off of the internal Create 2's battery. Note that the battery voltage can be as high as ~21V so a buck converter such as this one could be good for getting the unregulated Vpwr from 20V down to a more reasonable 5V