The Arduino Leonardo is a microcontroller board based on the exciting USB-enabled ATmega32u4 (datasheet). This chip has about the same amount of flash, RAM and capability as the ATmega328 found in the UNO. It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro 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 Leonardo differs from all preceding boards in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary chip (such as an FTDI friend, FTDI cable or the USB/Serial converter on the UNO). On one hand this means that sketches on the Leo are a little bigger because it’s also handling USB interaction. On the other hand, it allows the Leonardo to appear to a connected computer as a mouse and/or keyboard, in addition to a virtual (CDC) serial / COM port. It also has other implications for the behavior of the board; these are detailed on the getting started page.
Please note that this board is different than the UNO and so is best used by people with existing Arduino experience as there may be differences that trips up beginners. It is probably not going to work with shields designed for the UNO only. We’ve tested it with a bunch of shields and those that are compatible are noted in the description.
This board is only supported in the latest Arduino IDE 1.0.1 or higher