The classic beginner-friendly development board, built around ATmega328P.
| Pin | Name | Function | Type |
|---|---|---|---|
| D0 | D0 / RX | UART receive | BUS |
| D1 | D1 / TX | UART transmit | BUS |
| D2 | D2 | Digital I/O, external interrupt | I/O |
| D3 | D3 ~ | Digital I/O, PWM capable | I/O |
| D5 | D5 ~ | Digital I/O, PWM capable | I/O |
| D6 | D6 ~ | Digital I/O, PWM capable | I/O |
| D9 | D9 ~ | Digital I/O, PWM capable | I/O |
| D10 | D10 ~ | Digital I/O, PWM, SPI SS | BUS |
| D11 | D11 ~ | Digital I/O, PWM, SPI MOSI | BUS |
| D12 | D12 | Digital I/O, SPI MISO | BUS |
| D13 | D13 | Digital I/O, SPI SCK, onboard LED | I/O |
| A0 | A0 | Analog input 0 | ADC |
| A1 | A1 | Analog input 1 | ADC |
| A2 | A2 | Analog input 2 | ADC |
| A3 | A3 | Analog input 3 | ADC |
| A4 | A4 / SDA | Analog input 4, I2C data | BUS |
| A5 | A5 / SCL | Analog input 5, I2C clock | BUS |
| 5V | 5V | Regulated 5V output | PWR |
| 3V3 | 3.3V | Regulated 3.3V output | PWR |
| GND | GND | Ground | GND |
| VIN | VIN | Unregulated input voltage | PWR |
The Arduino UNO is the most popular microcontroller development board for beginners and hobbyists. Built around the ATmega328P, it exposes 14 digital I/O pins, 6 analog inputs, and standard headers compatible with hundreds of shields. Ideal for learning electronics and prototyping.