The Uno now uses an ATmega16U2 instead of the 8U2 found on the Uno (or the FTDI found on previous generations). This allows for faster transfer rates and more memory. No drivers needed for Linux or Mac (inf file for Windows is needed and included in the Arduino IDE), and the ability to have the Uno show up as a keyboard, mouse, joystick, etc.
The Uno R3 also adds SDA and SCL pins next to the AREF. In addition, there are two new pins placed near the RESET pin. One is the IOREF that allow the shields to adapt to the voltage provided from the board. The other is a not connected and is reserved for future purposes. The Uno R3 works with all existing shields but can adapt to new shields which use these additional pins.
Arduino is an open-source physical computing platform based on a simple i/o board and a development environment that implements the Processing/Wiring language. Arduino can be used to develop stand-alone interactive objects or can be connected to software on your computer (e.g. Flash, Processing, MaxMSP). The open-source IDE can be downloaded for free (currently for Mac OS X, Windows, and Linux).
* ATmega328 microcontroller
* Input voltage - 7-12V
* 14 Digital I/O Pins (6 PWM outputs)
* 6 Analog Inputs
* 32k Flash Memory
* 16Mhz Clock Speed
Main Changes from the older version:
1. TWI interface and the IOREF in the top and bottom connectors.This change keeps the board 100% compatible with the current boards and shields, but adds possibilities for new shields.
2. Reset button moved from center of board to corner near USB connector. This is great; makes it much easier to access with a shield on.
3. Larger heatsinking copper area for the LM117 regulator
4. Uses an Atmega16U2 instead of the Atmega8U2 on the previous version. Opens up more possibilities for USB apps!