Arduino Uno Pinout

Arduino Uno R3 is the board a whole generation of makers learned on. An ATmega328P microcontroller at 16 MHz, 5 V logic and a pin layout that hundreds of shields were built for.

Clones with a CH340 converter cost a fraction of the original and have the same pinout.

Specifications

ATmega328P: 8-bit AVR, 16 MHz
32 kB flash (0.5 kB used by the bootloader), 2 kB SRAM, 1 kB EEPROM
14 digital pins (6× PWM), 6 analog inputs (10-bit ADC)
UART, I2C (A4/A5 and separate SDA/SCL pins) and SPI (D10–D13 and the ICSP header)
5 V logic, 7–12 V power input (VIN or barrel jack) or USB power
USB-B with an ATmega16U2 converter (CH340 on clones)
68.6 × 53.4 mm

The newer Uno R4 (Minima and WiFi) has the same pin layout but a completely different 32-bit chip (Renesas RA4M1) – the pinout above applies to the classic R3 and its clones.

Pinout and pin table

Hover over a pin in the diagram or a table row; use the filter to highlight a bus. You can download the pinout as PNG or SVG.

Pin names:

Download:PNG SVG

License: CC BY 4.0 · How to credit

Pin table – Arduino Uno R3
Name	Chip port	Direction	UART	I2C	SPI	PWM	ADC	Note
NC		–						Nezapojeno (rezerva)
IOREF		output						Board logic level (5 V) – shields that support both 3.3 V and 5 V are configured according to it.
RESET		input						Reset – connecting to GND restarts the chip (same as the RESET button).
3V3		output						3.3 V output, max. 50 mA
5V		input/output						5 V from the regulator (when powered from the jack or VIN) or from USB; it can also power the board, but this bypasses the protection.
GND		–
GND		–
VIN		input						Power input 7–12 V. It sits after the power jack's protection diode – when powered from the jack it is 0.7–1 V lower; when powered via VIN, reverse-polarity protection does not work.
A0	PC0	input/output					ADC0
A1	PC1	input/output					ADC1
A2	PC2	input/output					ADC2
A3	PC3	input/output					ADC3
A4	PC4	input/output		SDA			ADC4	I2C SDA (Wire) – same as the SDA pin
A5	PC5	input/output		SCL			ADC5	I2C SCL (Wire) – same as the SCL pin
D0	PD0	input/output	RX					UART RX – shared with the USB-serial converter (program upload)
D1	PD1	input/output	TX					UART TX – shared with the USB-serial converter
D2	PD2	input/output						External interrupt INT0
D3	PD3	input/output				PWM		External interrupt INT1; PWM from Timer 2 (OC2B)
D4	PD4	input/output
D5	PD5	input/output				PWM		PWM from timer 0 (OC0B)
D6	PD6	input/output				PWM		PWM from timer 0 (OC0A)
D7	PD7	input/output
D8	PB0	input/output
D9	PB1	input/output				PWM		PWM from timer 1 (OC1A)
D10	PB2	input/output			SS	PWM		PWM from timer 1 (OC1B); SPI SS
D11	PB3	input/output			MOSI	PWM		PWM from timer 2 (OC2A); SPI MOSI (also on the ICSP header)
D12	PB4	input/output			MISO			SPI MISO (also on the ICSP header)
D13	PB5	input/output			SCK			SPI SCK (also on the ICSP header); onboard LED "L"
GND		–
AREF		input						ADC reference (default 5 V)
SDA	PC4	input/output		SDA				I2C SDA – propojeno s A4
SCL	PC5	input/output		SCL				I2C SCL – propojeno s A5

What to watch out for

D0 and D1 (UART) share the USB-serial converter – if anything is connected to them, uploading fails.
Draw at most 20 mA per pin (absolute maximum 40 mA) and no more than 200 mA from the whole chip.
The 3V3 pin supplies only 50 mA. USB is protected by a 500 mA resettable fuse.
SDA and SCL next to AREF are the same signals as A4 and A5 – don’t use them as analog inputs at the same time.
The Uno has no A6 and A7 analog inputs; those are on the Nano and Pro Mini.