Arduino UNO Rev 3: high-resolution pinout, datasheet, and specs

by Renzo Mischianti · Published 13 December 2023 · Updated 13 December 2023

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The Arduino Uno is a microcontroller board that serves as a fundamental tool for electronics and coding enthusiasts, educators, and professionals in the development of interactive projects. It’s built around the ATmega328P microcontroller and offers a user-friendly interface, making it an ideal choice for beginners and advanced users alike.

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The Arduino Uno is a widely-used microcontroller board based on the ATmega328P, and it comes with a variety of pinout configurations and technical specifications:

Pinout Configuration

Power: Vin, 3.3V, 5V, GND.
Reset: Resets the microcontroller.
Analog Pins (A0 – A5): Provide analog input in the range of 0-5V.
Digital I/O Pins (0 – 13): Can be used as input or output.
Serial (0 (Rx), 1 (Tx)): For TTL serial data transmission and reception.
External Interrupts (2, 3): To trigger interrupts.
PWM (3, 5, 6, 9, 11): Provide 8-bit PWM output.
SPI (10, 11, 12, 13): For SPI communication.
Inbuilt LED (13): Controls the built-in LED.
TWI (A4, A5): For TWI communication.
AREF: Reference voltage for input voltage.

Technical Specifications

Microcontroller: ATmega328P (8-bit AVR family).
Operating Voltage: 5V.
Recommended Input Voltage: 7-12V.
Input Voltage Limits: 6-20V.
Analog Input Pins: 6 (A0 – A5).
Digital I/O Pins: 14 (6 provide PWM output).
DC Current on I/O Pins: 40 mA.
DC Current on 3.3V Pin: 50 mA.
Flash Memory: 32 KB (0.5 KB for Bootloader).
SRAM: 2 KB.
EEPROM: 1 KB.
Frequency (Clock Speed): 16 MHz

The function of ATmega16U2 on the Arduino Uno

The ATmega16U2 on the Arduino Uno serves a specific and important function. It acts as a USB-to-serial converter, translating data between the computer’s USB interface and the main microcontroller’s serial communication lines. This functionality is crucial for the Arduino Uno as it allows for:

Programming: The ATmega16U2 enables the Arduino Uno to be programmed via a USB connection. It receives code from the Arduino IDE (or other programming environments) on the computer and passes it to the main microcontroller (ATmega328P) for execution.
Serial Communication: It also allows the ATmega328P to communicate with the computer during normal operation, facilitating the sending and receiving of data to and from the Arduino.

This use of a dedicated USB-to-serial chip is a significant upgrade from older Arduino models, which used an FTDI USB-to-serial driver chip. The ATmega16U2 is programmable itself, offering additional flexibility and customizability for advanced users who want to modify its firmware to suit specific USB communication requirements.