Arduino Uno R3

Note: This product is manufactured in Italy by affiliates of Arduino Srl, and the product packaging suggests downloading the Arduino IDE from arduino.org. However, we use and recommend using the normal Arduino IDE from arduino.cc, which is the IDE we ensure our Arduino libraries work with.

Arduino Uno R3, top view.

Overview

The Arduino Uno is a microcontroller board based on the ATmega328. It has 20 digital input/output pins (of which 6 can be used as PWM outputs and 6 can be used as analog inputs), a 16 MHz resonator, a USB connection, a power jack, an in-circuit system programming (ICSP) header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer (or appropriate wall power adapter) with a USB cable or power it with a AC-to-DC adapter or battery to get started.

The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features an ATmega16U2 programmed as a USB-to-serial converter. This auxiliary microcontroller has its own USB bootloader, which allows advanced users to reprogram it.

The Arduino has a large support community and an extensive set of support libraries and hardware add-on “shields” (e.g. you can easily make your Arduino wireless with our Wixel shield), making it a great introductory platform for embedded electronics. Note that we also offer a SparkFun Inventor’s Kit, which includes an Arduino Uno along with an assortment of components (e.g. breadboard, sensors, jumper wires, and LEDs) that make it possible to create a number of fun introductory projects.

This is the 3rd revision of the Uno (R3), which has a number of changes:

• The USB controller chip changed from ATmega8U2 (8K flash) to ATmega16U2 (16K flash). This does not increase the flash or RAM available to sketches.
• Three new pins were added, all of which are duplicates of previous pins. The I2C pins (A4, A5) have been also been brought out on the side of the board near AREF. There is a IOREF pin next to the reset pin, which is a duplicate of the 5V pin.
• The reset button is now next to the USB connector, making it more accessible when a shield is used.

Warning: We recommend not connecting the Arduino to USB while it is powered through VIN. See this forum post for more information.

Choosing the right controller

The table below compares the Arduino Uno, Leonardo, and our A-Star 32U4 Prime controllers. The A-Star Primes are based on the same ATmega32U4 AVR microcontroller as the Leonardo and ship with Arduino-compatible bootloaders. The Primes also offer many advantages, including superior power management that enables efficient operation from 2.7 V to 11.8 V (LV version) or 5 V to 36 V (SV version).

		Arduino Uno R3	Arduino Leonardo	A-Star 32U4 Prime LV	A-Star 32U4 Prime SV
Microcontroller:		ATmega328P	ATmega32U4	ATmega32U4
Clock:		16 MHz resonator	16 MHz crystal	16 MHz crystal
User I/O lines:		20	23	26
PWM outputs:		6	7	7
Analog inputs:		6	12	12
Ground access points:		4	4	43
User LEDs:		3	3	3
User pushbuttons:		—	—	3
Reset button:
Power switch:
Buzzer option:
microSD option:
LCD option:
Arduino-compatible bootloader:
USB connector:		B	Micro-B	Micro-B
USB/regulator power selection:		partial	partial	TPS2113A
High-performance reverse-voltage protection:
Recommended input voltage:		7 V to 12 V	7 V to 12 V	2.7 V to 11.8 V	5 V to 36 V
Regulator type (5 V):		linear	linear	switching step-up/step-down	switching step-down
Available 5 V output current:	at 3 V in	—	—	0.75 A	—
	at 5 V in	—	—	1.5 A	0.2 A
	at 7 V in	1.0 A	1.0 A	1.5 A	1.0 A
	at 9 V in	0.5 A	0.5 A	1.5 A	1.0 A
	at 11 V in	0.35 A	0.35 A	1.5 A	1.0 A
	at 24 V in	—	—	—	1.0 A
	via USB connector	0.5 A(1)	0.5 A(1)	1.5 A(1)	1.5 A(1)
Weight:		28 g	20 g	13 g to 33 g

1 With sufficiently capable USB power supply.

Side-by-side comparison of the A-Star 32U4 Prime LV microSD to the Arduino Leonardo.