The Leonardo differs from preceding boards in that it has built-in USB communication, removing the need for a secondary processor. This allows the Leonardo to appear to a connected computer as an HID, such as a mouse or keyboard, in addition to a virtual (CDC) serial / COM port. The Leonardo board contains everything needed to support the microcontroller. Simply connect it to a computer with a USB cable, or power it with an AC-to-DC adapter or battery, to get started.
According to Russell Rasor, Mouser Vice President of Advanced Technology, “Arduino has created a simple, yet powerful development board that is destined to become a favourite for programmers. Leonardo combines two functions into a single processor, allowing for greater flexibility in its communication with the computer. It will save design engineers valuable design time and money as it comes with everything ready to support the microcontroller.”
Gianluca Martino, Co-Founder of the Arduino Project, adds, “Our Leonardo AVR Dev Board is based on the proven and reliable Atmel 8-bit ATmega32u4 microcontroller to provide the flexibility and horsepower for this multi-functional tool. This single processor, controlling both the USB communication and sketches, and helps lower the cost by eliminating the additional processor.”