Arduino UNO Rev3 Pinout Diagram

Arduino UNO Rev3 Pinout Diagram | Generated by AI

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Question: what’s this PDF? (https://docs.arduino.cc/resources/pinouts/A000066-full-pinout.pdf)

Answer:

This is the Arduino UNO Rev3 (SKU A000066) full pinout diagram. It is basically a map showing every pin on the Arduino board and what each pin connects to internally. (Arduino Documentation)

Think of it like the “motherboard manual” for a tiny microcontroller board.

The board:

MCU: ATmega328P
Clock: 16 MHz
Logic voltage: 5V
Digital GPIO: 14 pins (D0-D13)
Analog inputs: 6 pins (A0-A5)
Flash: 32 KB
SRAM: 2 KB
EEPROM: 1 KB (Arduino Official Store)

Main sections in the pinout

1. Digital pins (D0-D13)

These are general-purpose input/output pins.

Example:

D13 ---- LED_BUILTIN
D12 ---- GPIO
D11 ---- PWM / SPI MOSI
D10 ---- PWM / SPI SS
D9  ---- PWM
D8  ---- GPIO
...
D0  ---- UART RX
D1  ---- UART TX

You can write:

pinMode(13, OUTPUT);

digitalWrite(13, HIGH);

to turn on the onboard LED.

2. Analog pins (A0-A5)

These connect to the ADC inside ATmega328P.

Example:

Sensor output
      |
      v
     A0
      |
      v
10-bit ADC
      |
      v
0 ~ 1023 value

Code:

int value = analogRead(A0);

If voltage is:

0V    -> 0
5V    -> 1023

3. Power pins

The PDF shows:

VIN
5V
3.3V
GND
RESET
IOREF

Typical usage:

External 7-12V
       |
       v
      VIN

Arduino regulator

       |
       +---- 5V rail

4. Communication pins

Arduino exposes several hardware protocols.

UART

D0 RX
D1 TX

Used for serial communication:

Arduino <---- USB serial ----> PC

SPI

Pins:

D10 SS
D11 MOSI
D12 MISO
D13 SCK

Used for:

SD cards
displays
fast sensors

Example:

Arduino
  |
 SPI
  |
SD card

I2C

Pins:

A4 SDA
A5 SCL

Used for:

OLED displays
IMU sensors
RTC modules

Example:

Arduino

A4 SDA -------- Sensor SDA
A5 SCL -------- Sensor SCL

The interesting part: Arduino pin numbers vs MCU pins

The Arduino abstraction hides the actual chip pins.

Example:

Arduino:

D13

actually maps to:

ATmega328P PB5

The PDF helps translate:

Arduino pin
      |
      v
ATmega328P register
      |
      v
hardware port

For low-level programming:

PORTB |= (1 << PB5);

is the same as:

digitalWrite(13, HIGH);

but much faster.

Why this PDF matters

For beginners:

Arduino pin
      |
      v
Connect LED / sensor / motor

For embedded engineers:

Arduino pin
      |
      v
ATmega328P GPIO
      |
      v
AVR register
      |
      v
hardware peripheral

It is the equivalent of a GPU block diagram or motherboard PCIe lane diagram, but for a microcontroller.

For your AI hardware background, the analogy:

Arduino pinout PDF
        ≈
NVIDIA GPU architecture diagram
        ≈
server motherboard block diagram

It tells you the physical resource map.

References:

Arduino UNO R3 documentation (Arduino Documentation)
Arduino UNO Rev3 technical specifications (Arduino Official Store)
Arduino UNO R3 datasheet (Arduino Documentation)

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