Arduino Nano Pinout

Overview

This guide covers the classic Arduino Nano: a breadboard-friendly board built around the ATmega328P, the same chip as the Arduino Uno, just on a smaller DIP-style footprint. No Wi-Fi, no Bluetooth, this is a plain 5V AVR board, which is exactly why it’s still a common choice for simple, no-nonsense projects.

Getting started

The Nano ships with three different USB connectors depending on the revision and clone: original Mini-USB, most common Micro-USB, or newer USB-C boards. Check which one your board actually has before assuming you’re missing a cable.

Hello World: blink an LED

The microcontroller equivalent of “Hello World”: the onboard “L” LED on D13 toggles once a second. No wiring needed, this LED is already built into the board. There’s no ESP-IDF equivalent here, the Nano only speaks Arduino’s AVR toolchain.

#define LED_PIN 13 // onboard "L" LED
void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  delay(1000);
  digitalWrite(LED_PIN, LOW);
  delay(1000);
}

Select Tools → Board → Arduino Nano first, see “Getting started” above.

Specifications

Official specifications for the ATmega328P-based Arduino Nano.

Pinout diagram

Every pin on the Arduino Nano, including the underlying ATmega328P port names (PB/PC/PD) alongside the Arduino digital/analog numbering.

GPIO quick reference

A4/A5 are the default I2C pins, D11–D13 the default SPI pins, both shared with the analog/digital pins listed below.

Programming (USB)

Unlike the ESP32 boards in these guides, the Nano has no manual boot-mode pin to hold. An onboard USB-to-serial chip toggles RESET automatically (via the DTR line) when you click Upload, that’s also why D0/D1 briefly glitch at power-up, they’re shared with that same USB-serial link.

Safety notes