Arduino Uno R3 is a development board based on the ATmega328P. It has 14 digital input/output pins , 6 analog inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button. 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. The Uno R3 differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega16U2 programmed as a USB-to-serial converter. The Arduino UNO can be powered via the USB connection or with an external power supply (from 7V to 12V). The power source is selected automatically. External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector