microcontrollers / arduino-uno.md

Arduino Uno R3

The classic ATmega328P board. 14 digital I/O, 6 analog inputs, 32 KB flash, USB-B. The reference 5 V Arduino for almost every beginner tutorial.

In stock CC-BY-SA-4.0 4 files · 2.6 MB

Specs

Spec	Value
MCU	ATmega328P
Clock	16 MHz
Operating voltage	5 V
Input voltage (DC jack)	7–12 V
Digital I/O	14 (6 PWM)
Analog inputs	6
Flash / SRAM / EEPROM	32 KB / 2 KB / 1 KB
USB	Type-B

Pinout summary

Pin	Function
D0 / D1	UART RX / TX
D2, D3	External interrupts (INT0, INT1)
D3, D5, D6, D9, D10, D11	PWM (~490 Hz)
D10–D13	SPI (SS, MOSI, MISO, SCK)
A4 / A5	I²C (SDA / SCL)
A0–A5	10-bit ADC inputs
3V3	50 mA regulator output
5V	USB / regulator output

Full graphical pinout: A000066-full-pinout.pdf.

Wiring example — Blink on D13

const int LED = 13;       // Built-in LED on D13

void setup() {
  pinMode(LED, OUTPUT);
}

void loop() {
  digitalWrite(LED, HIGH);
  delay(500);
  digitalWrite(LED, LOW);
  delay(500);
}

Connect: USB cable from PC → Arduino Uno. Open Arduino IDE → select Arduino Uno + correct COM port → upload.

Schematic

The Uno R3 schematic is published by Arduino under CC-BY-SA-4.0 at docs.arduino.cc/hardware/uno-rev3.

Open schematic (PDF)

Related

• Arduino Nano — same MCU in a smaller board
• L298N motor driver — drive DC motors from Uno
• HC-SR04 ultrasonic sensor — distance sensing demo
• Learn: Getting started with Arduino

Last updated: 2026-05-13 · Source on GitHub