Arduino Uno Pinout
Arduino Uno R3 · ATmega328P, Uno R3 form factor
Fourteen digital pins, six analog, and a handful with second jobs — PWM, interrupts, SPI and I²C — which is what the pinout is usually consulted for.
| Pin | Name | Function |
|---|---|---|
| 0 | RX | UART receive — shared with USB |
| 1 | TX | UART transmit — shared with USB |
| 2 | D2 | External interrupt 0 |
| 3 | D3 ~ | PWM, external interrupt 1 |
| 5 | D5 ~ | PWM |
| 6 | D6 ~ | PWM |
| 9 | D9 ~ | PWM |
| 10 | D10 ~ | PWM, SPI SS |
| 11 | D11 ~ | PWM, SPI MOSI |
| 12 | D12 | SPI MISO |
| 13 | D13 | SPI SCK, on-board LED |
| A4 | A4 | Analog in, I²C SDA |
| A5 | A5 | Analog in, I²C SCL |
Things that catch people out
- Pins 0 and 1 are wired to the USB-serial bridge — using them breaks uploads.
- 40 mA absolute max per pin, 200 mA total across the chip.
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