Arduino Nano is a surface mount breadboard embedded version with integrated USB. It is a smallest, complete, and breadboard friendly. It has everything that Diecimila/Duemilanove has (electrically) with more analog input pins and onboard +5V AREF jumper. Physically, it is missing power jack. The Nano is automatically sense and switch to the higher potential source of power, there is no need for the power select jumper.
Nano’s got the breadboard-ability of the Boarduino and the Mini+USB with smaller footprint than either, so users have more breadboard space. It’s got a pin layout that works well with the Mini or the Basic Stamp (TX, RX, ATN, GND on one top, power and ground on the other). This new version 3.0 comes with ATMEGA328 which offer more programming and data memory space. It is two layers. That make it easier to hack and more affordable.
Microcontroller Atmel ATmega328
Operating Voltage (logic level) 5 V
Input Voltage (recommended) 7-12 V
Input Voltage (limits) 6-20 V
Digital I/O Pins 14 (of which 6 provide PWM output)
Analog Input Pins 8
DC Current per I/O Pin 40 mA
Flash Memory 32 KB (of which 2KB used by bootloader)
SRAM 2 KB
EEPROM 1 KB
Clock Speed 16 MHz
• Automatic reset during program download
• Power OK blue LED
• Green (TX), red (RX) and orange (L) LED
• Auto sensing/switching power input
• Small mini-B USB for programming and serial monitor
• ICSP header for direct program download
• Standard 0.1” spacing DIP (breadboard friendly)
• Manual reset switch
The Arduino Nano 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 power source is automatically selected to the highest voltage source.