Raspberry Pi pin mappings

You need to know which physical header pins on the Raspberry Pi correspond to which pin numbers you access in your code. For example the pin 37 (second from bottom left pin) maps on GPIO 26. There is a very helpful document on the Microsoft web site that gives you the pin mappings, but for convenience I’ve also summarised the information in the following table:

GPIO#	Power-on Pull	Alternate Functions	Header Pin
2	PullUp	I2C1 SDA	3
3	PullUp	I2C1 SCL	5
4	PullUp		7
5	PullUp		29
6	PullUp		31
7	PullUp	SPI0 CS1	26
8	PullUp	SPI0 CS0	24
9	PullDown	SPI0 MISO	21
10	PullDown	SPI0 MOSI	19
11	PullDown	SPI0 SCLK	23
12	PullDown		32
13	PullDown		33
16	PullDown	SPI1 CS0	36
17	PullDown		11
18	PullDown		12
19	PullDown	SPI1 MISO	35
20	PullDown	SPI1 MOSI	38
21	PullDown	SPI1 SCLK	40
22	PullDown		15
23	PullDown		16
24	PullDown		18
25	PullDown		22
26	PullDown		37
27	PullDown		13
35*	PullUp		Red Power LED
47*	PullUp		Green Activity LED

* = Raspberry Pi 2 ONLY. GPIO 35 & 47 are not available on Raspberry Pi 3.