In this article:
- The standard line of ATmega328P-based UNO boards
- Other UNO boards from Arduino
- Arduino-compatible UNO boards by other manufacturers
The standard line of ATmega328P-based UNO boards
While “Arduino UNO” was also the name of the first Arduino UNO board model, it is now more often used to refer to any board with these characteristics:
- Uses the Arduino UNO layout
- ATmega328P microcontroller
- Uses the
Arduino Unoboard core from the Arduino AVR Boards package
Today, the Arduino UNO R3 is the main successor to this line of boards, and the most popular official Arduino UNO board.
Arduino UNO R3
Microcontroller: ATmega328P
Board core: Arduino Uno (Arduino AVR Boards)
Store page: Arduino Uno Rev3
Documentation: UNO R3
Revision 3 of the board has the following new features:
- 1.0 pinout: Added SDA and SCL pins that are near to the AREF pin and two other new pins placed near to the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board.
- Stronger RESET circuit.
- The ATmega8U2 USB-to-serial chip was replaced with ATmega16U2.
See also: Overview of the Arduino UNO Components
Arduino UNO R3 SMD
Microcontroller: ATmega328P
Board core: Arduino Uno (Arduino AVR Boards)
Store page: Arduino Uno Rev3 SMD
Documentation: UNO R3 SMD
On the SMD (Surface Mounted Device) version of the UNO R3, the ATmega328 microprocessor is soldered directly on the board. This means it cannot easily be replaced like on the standard UNO R3.
Arduino UNO Rev3 with Long Pins
Microcontroller: ATmega328P
Board core: Arduino Uno (Arduino AVR Boards)
Documentation: Arduino UNO Rev3 with Long Pins
A version of the UNO R3 with longer pins on the bottom.
Arduino UNO Rev2
Microcontroller: ATmega328P
Board core: Arduino Uno (Arduino AVR Boards)
This revision added a resistor pulling the ATmega8U2 HWB line to ground, making it easier to set to DFU mode.
Arduino UNO
Microcontroller: ATmega328P
Board core: Arduino Uno (Arduino AVR Boards)
Documentation: ARDUINO UNO
The original UNO board. It is sometimes refered to as the “R1” or “Rev1” version to distinguish it from later versions.
Other UNO boards from Arduino
UNO WiFi Rev2
Microcontroller: ATmega4809
Board core: Arduino Uno Wifi Rev2 (Arduino megaAVR Boards)
Store page: ARDUINO UNO WiFi REV2
Documentation: UNO WiFi Rev2
Noticeably, the UNO WiFi Rev2 features an ATmega4809 microprocessor instead of the ATmega328P microprocessor used on the original UNO WiFi and all other UNO boards. When selecting your board in Arduino IDE it’s important to differentiate between Arduino Uno Wifi (Arduino AVR Boards) and Arduino Uno Wifi Rev2 (Arduino megaAVR Boards), and select the correct one for your board.
The only UNO board that comes with an ATmega4809 microprocessor instead of an ATmega328P. The u-blox NINA-W102 enables Bluetooth® and Wi-Fi connectivity.
Arduino UNO WiFi
Microcontroller: ATmega328P
Board core: Arduino Uno WiFi (Arduino AVR Boards)
Documentation: Arduino Uno WiFi
A version of the UNO R3 with an ESP8266 Wi-Fi module.
Not to be confused with the Arduino UNO WiFi Rev2.
UNO Mini Limited Edition
Microcontroller: ATmega328P
Board core: Arduino Uno Mini (Arduino AVR Boards)
Store page: Arduino UNO Mini Limited Edition
Documentation: UNO Mini Limited Edition
This limited edition UNO board comes in a smaller form factor, and has a USB-C connector.
Arduino-compatible “UNO” boards by other manufacturers
There exists a variety of clone and derivative boards, as well as other products marketed as “Arduino-compatible”, with “UNO” in the name.
Most Arduino-compatible “UNO” boards available today are based on the Arduino UNO R3 and can be used with the main Arduino Uno (Arduino AVR Boards) core. They may use USB-to-serial chips that require additional drivers. Consult the manufacturer’s documentation or contact your reseller for more information.
