Arduino Uno Pin Diagram: Pinout & Specifications 2025 (An Ultimate Guide)

"UNO" means one in Italian. This word was chosen to denote the launch of Arduino Software (IDE) 1.0. The UNO board and version 1.0 of Arduino Software (IDE) were the reference versions that have now been developed. Both beginners and professionals should learn the concepts of Arduino Uno pinout to become experts in microcontroller programming and build amazing projects.

Arduino Uno is a microcontroller that is commonly used in various applications in the electronics field. It can be quite useful in electronic projects and prototyping. We provide you with a complete understanding of the pin diagram of Arduino Uno, which is essential to ensure that the circuit is designed efficiently. This guide also explores the various components of Arduino UNO pins, such as digital, analog, timer, interrupt, and I/O pins. We will explain their functions in detail to help you enhance your Arduino development skills.

What is Arduino Uno?

Arduino Uno is a very popular microcontroller development board. It is built on the 8-bit ATmega328P microcontroller. Other major components of this controller are a crystal oscillator, serial communication, voltage regulator, etc., without these components supporting the microcontroller, it will not function as intended. It has 14 digital input/output pins. Some of them are digital I/O pins, analog input pins, and power pins. It also has other components like a crystal oscillator, serial communication, voltage regulator, etc. which support the microcontroller.

Benefits of Arduino Uno

• Arduino Uno hardware is user-friendly.
• It is equipped with a complete support system for the microcontroller.
• It can easily work with a computer with a USB cable or an AC-to-DC adapter or battery.

How Is Arduino Uno Beneficial for Both Novice and Advanced Engineers

The Arduino Uno has an open-source platform. It is useful in the following ways:

• Provides all the resources needed for project ideation.
• It can help in completing educational projects, prototyping, and various DIY electronics projects at both beginner and advanced levels.
• It is also easy for anyone to learn as it uses the C++ language, which is a well-known, widely used, and accepted programming language.

Arduino Uno Pin Diagram

This diagram shows the pins on the board in graphical form. Its main utility is to understand where the pins are located and how they work easily and quickly. It has 14 digital I/O pins, 6 analog pins, 4 power pins, 1 reset pin, and an ICSP header.

Input and Output Pins of Arduino UNO

All 14 digital pins on the Arduino UNO are used as inputs or outputs. This is possible through the following functions:

• pinMode()
• digitalWrite()
• digitalRead()

They operate at 5 volts. Each pin can supply or receive 20mA, which is its recommended operating condition. It has an internal pull-up resistor of 20-50k ohms, which is disconnected by default. You have to make sure that the value on any I/O pin does not exceed 40mA because otherwise, it can permanently damage the microcontroller.

Arduino Uno Pin Diagram & Configuration

Arduino uno pin configuration has a specific purpose, and each pin has a specific function. The role of each pin is as follows:

• Serial: The role of serial 0 (RX) and 1 (TX) is to receive and transmit (RX) TTL serial data. These pins are connected to the corresponding pins of the ATmega8U2 USB-to-TTL serial chip.
• External interrupts: Pins 2 and 3 are set and trigger interrupts on a low value, a rising or falling edge, or a change in value. You can check the attachInterrupt() function for more details.
• PWM: 3, 5, 6, 9, 10, and 11 provide 8-bit PWM output with the analogWrite() function.
• SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). There is SPI communication support on these pins with the help of the SPI library.
• LED: LED integrated into digital pin 13. The LED is on when the pin is high and off when the pin is low.
• TWI: Supports TWI communication using the A4 or SDA pin and the A5 or SCL pin wire library.
• The UNO has 6 analog inputs. They are labeled A0 to A5. Each pin transmits 10 bits of resolution. Their default measurement is 5 volts from the ground. You can change the upper end of their range using the AREF pin and the analogReference() function.
• AREF: AREF is the reference voltage for the analog inputs and is used with analogReference().

Power Pins

The Arduino Uno has several power pins that are used to power the board or any other device. Each power pin has a specific purpose. This is the use of each power pin.

• 5V Pin: This pin is the pin that provides a regulated 5V DC output. It is useful for powering other devices that require 5V DC.
• 3.3V Pin: This pin is the pin that provides a regulated 3.3V DC output. It is applicable for powering other devices that require 3.3V DC.
• GND Pins: The GND pin is the pin that is used to connect the board to the ground. Its main purpose is to complete the circuit and provide a reference voltage.
• VIN Pin: This pin is used to power the board using an external power source. Its voltage range is between 7V and 12V DC.

Other Pins

Other pins in the Arduino Uno are also important. Each pin serves a specific purpose: Let's look at them one by one:

• Reset: The reset pin resets the board. This happens when the pin is set to LOW.
• ICSP Header: The function of the ICSP header is to program the board. To do this, you need to take the help of an external programmer.

The USB connection is used to program the board and communicate with other devices.

FAQs: Questions & Answers

Q1. What Is The Best Power Source for Arduino Uno?

The barrel jack is the best way to power an Arduino Uno when your project is ready to use. It works with a 2.1mm center-positive plug from an adapter that gives between 7V and 12V.

Q2. What Is The Function of PWM Pins on Arduino UNO?

PWM helps in many ways:

• Controls LED brightness.
• It acts like an analog output by changing voltage between 0% and 100% when filtered.
• Creates sound signals.

Q3. Can You Power an Arduino With More Than 5V?

Not without extra cooling. A 12V supply is too high for the built-in voltage regulator in most cases. It’s better to use a 7.5V or 9V adapter with the barrel jack to power an Arduino Uno. A DC/DC converter can handle 12V without overheating.

Read Next: Understanding Dual Power Supply: Circuit Construction and Working