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Raspberry Pi GPIO - reference

This is the reference guide to the Raspberry Pi GPIO ports. For an overview and projects relating to the Raspberry Pi then see the Raspberry Pi Tutorials page.

Raspberry Pi Linux computer The Raspberry Pi is an ideal computer for use in physical computing thanks to its GPIO connector. This is a mulit-way male connector with either 26 or 40 pins. These pins can supply power, logic level input and output (3.3V only) and other connection types such as PWM, SPI, I2C and Serial. This flexibility provides many different ways to connect to the real world through electronic componenets.

Raspberry Pi GPIO pin numbers: board vs GPIO numbers

Confusingly the pins can have different numbers assigned to them depending upon whether you look at their physical position or on how they are used.

The GPIO connector can be used as a single connector (eg. by connecting a HAT or using a 40-way connector), but they are also individual pins which can be individually numbered. With the SD card slot positioned at the top then the top-left is pin 1 and top-right is pin 2. They are then numbered from left to right as you work your way down the connector. This is sometimes referred to as the board pin number which is useful for identifying the physical pin. When writing code then they are more often referred to by a different number.

The connectors mostly connect directly to the pins on the Broadcom processor (CPU). As a result many have a GPIO reference which relates to how it connects to the processor. This is the number that is most commonly used when writing code to refer to the GPIO ports.

The diagram below shows how the pins are physically positioned and some for the different purposes for the pins.

Raspberry Pi GPIO pin layout

Table of GPIO ports on the Raspberry Pi

The table below shows the ports and the primary and altenative uses.

Pin number

GPIO port

Alternative function

Comments

1

 

3.3V power supply

 

2

 

5V power supply

 

3

GPIO 2

SDA1 (I2C data)

Changed from revision 1 boards

4

 

5V power supply

 

5

GPIO 3

SCL1 (I2C clock)

Changed from revision 1 boards

6

 

Ground

 

7

GPIO 4

 

 

8

GPIO 14

Serial / console TXD

Serial transmit

9

 

Ground

 

10

GPIO 15

Serial / console RXD

Serial receive

11

GPIO 17

 

 

12

GPIO 18

PWM

Pulse Width Modulation

13

GPIO 27

 

Changed from revision 1 boards

14

 

Ground

 

15

GPIO 22

 

 

16

GPIO 23

 

 

17

 

3.3V

 

18

GPIO 24

 

 

19

GPIO 10

MOSI (SPI)

SPI Master Output, Slave Input

20

 

Ground

 

21

GPIO 9

MISO (SPI)

SPI Master Input, Slave Output

22

GPIO 25

 

 

23

GPIO 11

SCLK (SPI)

SPI clock

24

GPIO 8

CE0 (SPI)

Chip Enable (slave select)

25

 

Ground

 

26

GPIO 7

CE1 (SPI)

Chip Enable (slave select)

27

 

ID_SD

For HAT EEPROM

28

 

ID_SC

For HAT EEPROM

29

GPIO 5

 

 

30

 

Ground

 

31

GPIO 6

 

 

32

GPIO 12

 

 

33

GPIO 13

 

 

34

 

Ground

 

35

GPIO 19

SPI1_MISO

 

36

GPIO 16

CE2 (SPI)

Chip Enable (slave select)

37

PIO 26

 

 

38

GPIO 20

SPI1_MOSI

 

39

 

Ground

 

40

GPIO 21

SPI1_CLK

 

Also see: Raspberry Pi tutorials and projects.

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