You need to look at the MCU datasheet for the pin assignments. MCUs will have a certain number of fixed-function pins, stuff like power supply and crystal oscillator connections, that do a single thing. On modern MCUs, most other pins will have a multiplexer that lets you choose from several different functions for the same pin. The kinds of peripherals the pins connect to varies and there's a lot of reading you can do on the various different kinds. You'll want to learn about general-purpose I/O (GPIO) pins and the difference between push-pull and open collector outputs, what a Schmitt trigger is (used on GPIO inputs), how counter/timers work, what a UART or USART is, and how I2C and SPI work for starters. I'd just go down the list for an MCU and check Wikipedia for an explanation of each type. Answer from madsci on reddit.com
Arduino
arduino.cc › en › Tutorial › DigitalPins
Digital Pins | Arduino Documentation
The pins on the Arduino can be configured as either inputs or outputs. This document explains the functioning of the pins in those modes.
The Robotics Back-End
roboticsbackend.com › home › arduino uno pins – a complete practical guide
Arduino Uno Pins - A Complete Practical Guide - The Robotics Back-End
August 22, 2023 - The Arduino Uno board has over 20 pins that you can use for many different applications. In this post I’ll give you a complete and practical overview of the main Arduino Uno pins. If you’re starting with Arduino, or if you’re already a software developer and want to learn more about the bridge between software ...
How do I learn what all the pins do?
A great question. I have changed your flair to "Mod's choice" which means we will highlight your post in our Monthly Digests . More on reddit.com
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October 17, 2025Understanding pin definitions to write Arduino code
Hello! I’m a beginner and struggling pin definitions in Arduino. paulvha started to set me straight over here: viewtopic.php?f=169&t=58525 but I’m moving on to adding buttons to my project and I’m clearly not getting it. I’m looking at the Schematic, Apollo3 Datasheet, and Integrations ... More on community.sparkfun.com
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Components101
components101.com › microcontrollers › arduino-uno
Arduino Uno Pinout, Specifications, Pin Configuration & Programming
Arduino Uno has 14 digital input/output pins (out of which 6 can be used as PWM outputs), 6 analog input pins, a USB connection, A Power barrel jack, an ICSP header and a reset button.
Reddit
reddit.com › r/arduino › how do i learn what all the pins do?
r/arduino on Reddit: How do I learn what all the pins do?
October 17, 2025 -
I am teaching myself the basics of electricity which isnt too bad. Just basic physics. However, actually knowing which pin does what (and why) is foreign to me right now. How did you guys learn?
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You need to look at the MCU datasheet for the pin assignments. MCUs will have a certain number of fixed-function pins, stuff like power supply and crystal oscillator connections, that do a single thing. On modern MCUs, most other pins will have a multiplexer that lets you choose from several different functions for the same pin. The kinds of peripherals the pins connect to varies and there's a lot of reading you can do on the various different kinds. You'll want to learn about general-purpose I/O (GPIO) pins and the difference between push-pull and open collector outputs, what a Schmitt trigger is (used on GPIO inputs), how counter/timers work, what a UART or USART is, and how I2C and SPI work for starters. I'd just go down the list for an MCU and check Wikipedia for an explanation of each type.
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Depending on your MCU, there are any number of diagrams that have various different ways to display what each pin can do. Just Google your MCU and “pin out” or something like that.
Circuit Design
circuito.io › blog › arduino-uno-pinout
The Full Arduino Uno Pinout Guide [including diagram] | circuito.io
November 18, 2018 - The Arduino Uno pinout consists of 14 digital pins, 6 analog inputs, a power jack, USB connection and ICSP header. The versatility of the pinout provides many different options such as driving motors, LEDs, reading sensors and more.
Robu.in
robu.in › arduino-pin-configuration
Arduino Pin Configuration - Complete Guide 2021
July 14, 2020 - GND: This pin of the board is used to ground the Arduino board. Reset: This pin of the board is used to reset the microcontroller.
Medium
medium.com › vicara-hardware-university › arduino-introduction-to-pins-723ecb97d2a0
Introduction to Pins. The Arduino Uno is one ... - Medium
November 10, 2020 - GND — Ground pin. ... An analog signal can take any number of values, while a digital signal which is limited to two values: High and Low. To measure the value of analog signals, the Arduino has a built-in analog-to-digital converter (ADC).
Arduino
arduino.cc › en › Reference › Board
Overview of the Arduino UNO Components | Arduino Documentation
July 10, 2025 - The Arduino UNO. ... Digital Pins 0-1/Serial In/Out - TX/RX (dark green) - These pins cannot be used for digital i/o (digitalRead and digitalWrite) if you are also using serial communication (e.g.
SparkFun Community
community.sparkfun.com › development boards › artemis
Understanding pin definitions to write Arduino code - Artemis - SparkFun Community
November 8, 2022 - Hello! I’m a beginner and struggling pin definitions in Arduino. paulvha started to set me straight over here: viewtopic.php?f=169&t=58525 but I’m moving on to adding buttons to my project and I’m clearly not getting it. I’m looking at the Schematic, Apollo3 Datasheet, and Integrations Guide here: https://www.sparkfun.com/products/15443.
Robocraze
robocraze.com › home › arduino pin configuration
Arduino Pin Configuration Explained for All Boards – Robocraze
July 9, 2022 - This pin on the board outputs 3.3V which can be power supply external components. This can be used to make the common ground for external circuits and Arduino boards.
NextPCB
nextpcb.com › home › blog › arduino nano pinout
The Ultimate Guide to Arduino Nano Pinout
April 27, 2023 - Digital I/O pins: Fourteen digital pins, six with PWM support. Control your devices and create complex projects. Operating voltage: Nano runs on 5V, making it compatible with a wide range of sensors and peripherals. UART, SPI, and I2C: Communication protocols abound, enabling seamless connection with various devices. Breadboard-friendly: Nano's design allows easy integration with breadboards. Prototype and develop without hassle. The Arduino Nano boasts 30 pins, 22 of which cater to input and output functions.
Robocraze
robocraze.com › home › arduino uno pin diagram: a complete guide
Arduino Uno Pin Diagram – Digital, Analog & Power Pins
June 17, 2026 - Understanding Arduino Uno pins explained starts with knowing that each pin serves a distinct role, from reading sensor data to driving motors to supplying power.
YouTube
youtube.com › watch
Arduino Uno - Pins Overview - YouTube
Complete Arduino Uno Pins overview. Understand what each pin does, and what are the hidden functionalities of the Arduino board.👉 Complete Arduino Course fo...
Published October 7, 2021
Starting Electronics
startingelectronics.org › beginners › arduino-tutorial-for-beginners › arduino-input-and-output-pins
Arduino Input and Output Pins | Starting Electronics
February 2, 2022 - In addition PWM pins are covered. ... Basically, Arduino digital pins are configurable between three different functions as follows. Firstly input pins for reading the state of a pin, or attached switch for example. Secondly as an output to switch or drive an electric load such as an LED.
ControllersTech®
controllerstech.com › home › arduino › core tutorials › arduino uno pinout
Arduino UNO Pinout – Complete Guide with Diagram (All Pins Explained)
June 1, 2026 - In this guide, we are going to walk through every pin on the Arduino UNO board. We will explain what it does, when to use it, and what to watch out for.
PCBSync
pcbsync.com › home › arduino information › arduino uno pinout explained: every pin you need to know
Arduino Uno Pinout Explained: Every Pin You Need to Know - PCBSync
March 4, 2026 - The 5V pin can supply approximately 500mA when powered via USB, or up to 1A when using an external power supply through the barrel jack. The 3.3V pin has a strict 50mA limit—exceeding this risks damaging the onboard regulator.
Last Minute Engineers
lastminuteengineers.com › arduino-pinout
Arduino UNO Pinout Reference
March 25, 2026 - These pins can be configured as either inputs or outputs. When set as inputs, they can read digital signals (HIGH or LOW), and when set as outputs, they can send digital signals to control external components like LEDs, motors, and relays.
SparkFun Learn
learn.sparkfun.com › tutorials › what-is-an-arduino › whats-on-the-board
What is an Arduino? - SparkFun Learn
NOTE: Do NOT use a power supply greater than 20 Volts as you will overpower (and thereby destroy) your Arduino. The recommended voltage for most Arduino models is between 6 and 12 Volts. The pins on your Arduino are the places where you connect wires to construct a circuit (probably in conjuction ...