Jetson TX2 J21 Header

GPIO16The GPIO numbering is different than the Jetson TX1 table.

Jetson TX2 J21 HeaderSysfs GPIONamePinPinNameSysfs GPIO 3.3 VDC
Power

1

2

5.0 VDC
Power  I2C_GP_DAT
General I2C #0 Data 3.3.V

3

4

5.0 VDC
Power  I2C_GP_CLK
General I2C #0 Clock 3.3.V

5

6

GND  AUDIO_MCLK
Audio Master Clock (1.8/3.3.V)

7

8

UART0_TX
UART #0 Transmit  GND

9

10

UART0_RX
UART #0 Receive  UART0_RTS#
UART #0 Request to Send

11

12

I2S0_SCLK
Audio I2S #0 Clock  GPIO_PE6
Audio Code Interrupt

13

14

GND  GPIO_EXP_P17_3V3
From GPIO Expander (P17)

15

16

AO_DMIC_IN_DAT_LVL
Unused  3.3 VDC
Power

17

18

GPIO16_MDM_WAKE_AP
Modem Wake AP GPIOgpio481 SPI_MOSI
SPI #1 Master Out/Slave In

19

20

GND  SPI1_MISO
SPI #1 Master In/Slave Out

21

22

GPIO_EXP_P16_3V3
From GPIO Epander (P16)  SPI_CLK
SPI #1 Shift Clock

23

24

SPI1_CS0#
SPI #1 Chip Select #0  GND

25

26

SPI1_CS1#
SPI #1 Chip Select #1  I2C_GP1_DAT
General I2C #1 Data (3.3V)

27

28

I2C_GP1_CLK
General I2C #1 Clock (3.3V) gpio398GPIO19_AUD_RST
Audio Reset (1.8/3.3V)

29

30

GND gpio298GPIO9_MOTION_INT
Motion Interrupt (3.3V)

31

32

AO_DMIC_IN_CLK
Unused gpio389GPIO11_AP_WAKE_BT
AP Wake Bt GPIO

33

34

GND  I2S0_LRCLK
AUDIO I2S #0 Left/Right Clock

35

36

UART0_CTS#
UART #0 Clear to Send gpio388GPIO8_ALS_PROX_INT
(3.3V)

37

38

I2S0_SDIN
Audio I2S #0 Data in  GND

39

40

I2S0_SDOUT
Audio I2S #0 Data in 

You can download the TX2 pinmux file to find the pin name and reference to tegra186-gpio.h to find the pin number. 
For example the pin 37 "GPIO8/ALS_PROX_INT" for TX2 is GPIO PQ4 then the pin number is 320 + (8x16 +4) = 452