The Arduino team is now shipping their latest creation – the Leonardo. It is the first Arduino to use Atmelʼs ATmegaXU4 series chip with built-in USB. This change is big and it has big benefits. In addition to the built-in USB, it offers more digital and analog pins. This comprehensive guide gives you the details you need to know to start using it – pinout differences, hardware capabilities, new software libraries and more.
Arduino Leonardo versus Uno – What’s New - [Link]