Arduino Uno Pinout

Arduino Uno is the most common-used board. Let's see its pinout and how to use it.

Hardware Required

1	×	Arduino UNO or Genuino UNO
1	×	USB 2.0 cable type A/B (for USB-A PC)
1	×	USB 2.0 cable type C/B (for USB-C PC)
1	×	(Recommended) Screw Terminal Block Shield for Arduino Uno
1	×	(Recommended) Breadboard Shield For Arduino Uno
1	×	(Recommended) Enclosure For Arduino Uno

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Arduino Uno Pinout

An Arduino Uno board has:

6 x Analog input pins. They can also be used as digital input/output pins
20 x digital input pins (14 x dedicated digital input + 6 x Analog input pins which can be used as digital input pins)
20 x digital output pins (14 x dedicated digital output + 6 x Analog input pins which can be used as digital output pins)
6 x PWM pins
1 x UART port
2 x I2C port (the same I2C bus)
1 x SPI port
1 x Reset pin
1 x 5v pin
1 x 3.3v pin
3 x GND pin

※ NOTE THAT:

For the pins are named with the prefix of 'D' (e.g. pin D1, D2 ...), It call be called without prefix of 'D', (e.g. pin 1, 2 ...)

Each pin can be used with diferent functionalities. However, at a time, each pin can be used only with one functionalitity.

Let's see how to use them

How To Use

Analog Input Pins

Applicable Pins: A0, A1, A2, A3, A4, A5

Each of analog input pins can be used as:

Analog input pin (default)
Digital input pin
Digital output pin

Related functions

Example Code

// example of how to use analog input pin void setup() { pinMode(A0, INPUT); // setup analog pin } void loop() { int reading = analogRead(A0); }

Because the pin is INPUT by default, you do not need to set up it.

// example of how to use analog input pin void setup() { } void loop() { int reading = analogRead(A0); }

※ NOTE THAT:

The pin A4 and A5 can be used for I2C communication. When they are used for I2C, do not use them as analog input.
All analog pins can be used as digital input/output pins. See the next part for how to use it.

Digital Input Pins

Applicable Pins:

A0, A1, A2, A3, A4, A5
D0, D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13

※ NOTE THAT:

Pin A0, A1, A2, A3, A4, A5 have other names: , D14, D15, D16, D17, D18, D19, respectively.

Related functions

Example Code

void setup() { pinMode(8, INPUT_PULLUP); // sets the digital pin D8 as input } void loop() { int val = digitalRead(8); // read the input pin }

It is the same for pin A0 to A5:

void setup() { pinMode(A2, INPUT_PULLUP); // sets the digital pin A2 as input } void loop() { int val = digitalRead(A2); // read the input pin }

Digital Output Pins

Applicable Pins:

A0, A1, A2, A3, A4, A5
D0, D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13

Related functions

Example Code

void setup() { pinMode(7, OUTPUT); // sets the digital pin D7 as output } void loop() { digitalWrite(7, HIGH); // control the output pin to HIGH delay(1000); // pause 1 sec digitalWrite(7, LOW); // control the output pin to LOW delay(1000); // pause 1 sec }

It is the same for pin A0 to A5:

void setup() { pinMode(A3, OUTPUT); // sets the digital pin A3 as output } void loop() { digitalWrite(A3, HIGH); // control the output pin to HIGH delay(1000); // pause 1 sec digitalWrite(A3, LOW); // control the output pin to LOW delay(1000); // pause 1 sec }

PWM pins

Applicable Pins: D3, D5, D6, D9, D10, D11

Related functions

Example Code

void setup() { pinMode(5, OUTPUT); // sets the pin D5 output } void loop() { analogWrite(5, 100); // analogWrite values from 0 to 255 }

UART Port

Applicable Pins: D0 (RX), D1 (TX)

See Arduino - Serial

I2C Port

Applicable Pin:

A4 (SDA), A5 (SCL)
D18 (SDA), D19 (SCL)

※ NOTE THAT:

Pin A4 is internally connected to pin D18
Pin A5 is internally connected to pin D19

Multipe I2C devices can share the same I2C bus. That is because the I2C devices are addressed by a value in data frame

SPI Port

Applicable Pin: MOSI(D11), MISO(D12), SCK(D13), SS(D10)

Please note that the SS pin is default to D10 and it can be changed

Reset Pin

If this pin is connected to GND, Arduino is reset.

5v Pin, 3.3v Pin, GND Pin

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Arduino Uno Pinout

Hardware Required

Arduino Uno Pinout

How To Use

Analog Input Pins

Related functions

Example Code

Digital Input Pins

Related functions

Example Code

Digital Output Pins

Related functions

Example Code

PWM pins

Related functions

Example Code

UART Port

I2C Port

SPI Port

Reset Pin

5v Pin, 3.3v Pin, GND Pin

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See Also