The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. It contains everything needed to support the microcontroller simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. It has 20 digital input/output pins (of which 6 can be used as PWM outputs and 6 can be used as analog inputs), a 16 MHz resonator, a USB connection, a power jack, an in-circuit system programming (ICSP) header, and a reset button. The Arduino Uno is a microcontroller board based on the ATmega328. The only difference between these versions is the microcontroller package. Due to the current scarcity of this part, a functionally identical version is available that uses a surface-mount-device equivalent AVR: the Arduino Uno SMD edition.
This Arduino Uno has a removable dual-inline-package (DIP) AVR. Discontinuation Notice: This Arduino Uno version has been replaced by a newer revision: Arduino Uno R3.
