The Mini-B USB port, a 6-20V unregulated external power supply (pin 30), or a 5V regulated external power supply are all options for powering the Arduino Nano (pin 27). The power source is automatically selected as the highest voltage source. The Arduino Nano V3.1 DFRobot USB Microcontroller V3.1 (ATMega 328) can be powered via the mini-B USB connection, 6-20V unregulated external power supply (pin 30), or 5V regulated external power supply (pin 27). The nano's pin layout works well with the Mini or the Basic Stamp (TX, RX, ATN, GND on one top, power and ground on the other). The Nano automatically senses and switches to the higher power supply, so there is no need for a power select jumper. The Nano has everything that the Diecimila has (electronically) with more analog input pins and an onboard +5V AREF jumper. Nano V3.1 by DFRobot Arduino Compatible - The Nano V3.1 by DFRobot Arduino Compatible is a breadboard-ready version of the Arduino mini with integrated USB.
