Mapping of Xavier NX GPIO pins to /sys/class/gpio/export

Robotics & Edge Computing Jetson & Embedded Systems Jetson Xavier NX
1

How can I check the correspondence between GPIO pins and /sys/class/gpio/export ?

3

Hi liuyuhangpro,

Are you using the devkit or custom board for Xavier NX?
What’s your Jetpack version in use?

Which pin would you like to control?
I could give an example for how to map them.

4

I’m using a custom board with JetPack version 4.6 (ver3), and the pins I need to control are GPIO0 to GPIO14. Can you provide an example mapping for GPIO3 (126)?

5

Let me take GPIO03 as example:

(1) Find this pin in pinmux spreadhseet

image
image3307×27 3.31 KB

=> You would know it is also PCC.00

(2) Run the following command on your board

$ sudo cat /sys/kernel/debug/gpio|grep PCC.00
 gpio-317 (PCC.00              )

=> You would know this pin is 317

(3) Export the pin and check its state

$ sudo su
# echo 317 > /sys/class/gpio/export
# cat /sys/class/gpio/PCC.00/direction
# cat /sys/class/gpio/PCC.00/value
6

Why is PCC.00 not being displayed?

nvidia@nx:~$ sudo cat /sys/kernel/debug/gpio | grep PCC.00
[sudo] password for nvidia:
nvidia@nx:~$ sudo cat /sys/kernel/debug/gpio | grep 317
 gpio-317 (                    )
nvidia@nx:~$
7

Oh sorry, it seems you are using the JP4 rather than JP5.
Please share the full dmesg for further check.

8

klog.txt (79.7 KB)
Yes, I am using JetPack 4.6 (ver3).

9

(1) run the following command on your board

$ sudo cat /sys/kernel/debug/gpio|grep aon
gpiochip1: GPIOs 248-287, parent: platform/c2f0000.gpio, tegra-gpio-aon:

=> You would know the base number for AON GPIO is 248

(2) refer to tegra194-gpio.h

#define TEGRA194_AON_GPIO(port, offset) \
  	((TEGRA194_AON_GPIO_PORT_##port * 8) + offset)
..
#define TEGRA194_AON_GPIO_PORT_CC 2

=> PCC.00 will result 16 (= 2*8 + 0)
=> You would know the gpio number for PCC.00 is 248+16 = 264

(3) Export the pin and check its state

$ sudo su
# echo 264 > /sys/class/gpio/export
# cat /sys/class/gpio/PCC.00/direction
# cat /sys/class/gpio/PCC.00/value
10

Alright, I understand. Thank you.

11

When I try to set GPIO04 (265), I get the following message. Is this pin already in use? How should I configure this pin as a GPIO?

root@nx:/sys/class/gpio# echo 265 > export
bash: echo: write error: Device or resource busy
root@nx:/sys/class/gpio#
12

Yes, it seems this pin has been used by others.
Please run the following command to check.

sudo cat /sys/kernel/debug/gpio|grep 265
14

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