ARDUINO Uno:

"Uno" means one in Italian and is named to mark the upcoming release of Arduino 1.0. The Uno and version 1.0 will be the reference versions of Arduino, moving forward. The Uno is the latest in a series of USB Arduino boards, and the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

Arduino Uno R3 is a new version of Uno with ATmega328 microcontroller. The Uno R3 differs from all preceding boards in that it does not use the FTDI USB-to-serial converter chip. Instead, it features the ATmega16U2 (ATmega8U2 in the revision 1 and revision 2 boards) programmed as a USB-to-serial converter. 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 maximum length and width of the Uno PCB are 2.7 and 2.1 inches respectively, with the USB connector and power jack extending beyond the former dimension. Four screw holes allow the board to be attached to a surface or case. Note that the distance between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil spacing of the other pins. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 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 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.

The Arduino Uno R3 requires the Arduino 1.0 drivers folder in order to install properly on some computers. We have tested and confirmed that the R3 can be programmed in older versions of the IDE. However, the first time using the R3 on a new computer, you will need to have Arduino 1.0 installed on that machine. If you are interested in reading more about the changes to the IDE, check out the official Arduino 1.0 Release notes!

Special SMD Version:

Because Atmel is moving more and more of their production capacity to surface mount ICs, the DIP packaged ATmega is becoming more and more difficult to get. To keep up with demand, we now offer the Arduino Uno R3 with an SMD ATmega. The board is identical to the PTH version of the Uno, but you won't be able to remove the ATmega without some hot-air. This change shouldn't affect most users. Besides - when was the last time you managed to destroy an ATmega and needed to repair an Arduino board? Those things are nearly indestructible.

Features:

Microcontroller                          ATmega328
Operating Voltage                      5V
Input Voltage (recommended)   7-12V
Input Voltage (limits)                 6-20V
Digital I/O Pins                         14 (of which 6 provide PWM output)
Analog Input Pins                      6
DC Current per I/O Pin             40 mA
DC Current for 3.3V Pin           50 mA
Flash Memory                           32 KB (ATmega328) of which 0.5 KB used by bootloader
SRAM                                       2 KB (ATmega328)
EEPROM                                  1 KB (ATmega328)
Clock Speed                              16 MHz

Important links:

                         EAGLE files: Arduino-uno-Rev3-reference-design.zip
                         Schematic: Arduino-uno-Rev3-schematic.pdf
                         Product page: Arduino-uno-Rev3-product page
                         Arduino IDE: Arduino-IDE-download

Note - The Arduino reference design can use an Atmega8, 168, or 328, Current models use an ATmega328, but an Atmega8 is shown in the schematic for reference. The pin configuration is identical on all three processors.

Not sure which Arduino or Arduino-compatible board is right for you? Check out our Arduino Buying Guide!