GPIO usage

This guide covers the Linux interface for GPIO operations using bash

Available GPIO's

The following output provides a list of all GPIO's that are available to the Jetson. This includes Tegra GPIO's as well as external driven GPIO extender.

If you want to do this Linux interface on a external connected GPIO extender, requires changes to the DeviceTree. A more detailed Instruction on how to implement such a device can be found in the Linux kernel Documentation.

Syntax: sudo cat /sys/kernel/debug/gpio

Debug gpio output

test@test-desktop:~$ sudo cat /sys/kernel/debug/gpio
[sudo] password for test: 
gpiochip1: GPIOs 316-347, parent: platform/c2f0000.gpio, tegra234-gpio-aon:
 gpio-316 (PAA.00              )
 gpio-317 (PAA.01              )
 gpio-318 (PAA.02              )
 gpio-319 (PAA.03              )
 gpio-320 (PAA.04              )
 gpio-321 (PAA.05              |fixed-regulators:reg) out hi 
 gpio-322 (PAA.06              )
 gpio-323 (PAA.07              )
 gpio-324 (PBB.00              )
 gpio-325 (PBB.01              )
 gpio-326 (PBB.02              )
 gpio-327 (PBB.03              )
 gpio-328 (PCC.00              )
 gpio-329 (PCC.01              )
 gpio-330 (PCC.02              )
 gpio-331 (PCC.03              |mux                 ) out hi 
 gpio-332 (PCC.04              )
 gpio-333 (PCC.05              )
 gpio-334 (PCC.06              )
 gpio-335 (PCC.07              )
 gpio-336 (PDD.00              )
 gpio-337 (PDD.01              )
 gpio-338 (PDD.02              )
 gpio-339 (PEE.00              )
 gpio-340 (PEE.01              )
 gpio-341 (PEE.02              )
 gpio-342 (PEE.03              )
 gpio-343 (PEE.04              |power-key           ) in  hi IRQ ACTIVE LOW
 gpio-344 (PEE.05              )
 gpio-345 (PEE.06              )
 gpio-346 (PEE.07              )
 gpio-347 (PGG.00              )
gpiochip0: GPIOs 348-511, parent: platform/2200000.gpio, tegra234-gpio:
 gpio-348 (PA.00               |fixed-regulators:reg) out lo 
 gpio-349 (PA.01               )
 gpio-350 (PA.02               )
 gpio-351 (PA.03               )
# And so on...

The GPIO numbers listed in the Linux operating system do not match with the numbers of the Jetson socket pins.

Export GPIO

At first, you have to export the GPIO that you want to use in the Linux file system in order to configure and read or write data from it.

Syntax: echo <GPIO_NR> > /sys/class/gpio/export

export gpio

nvidia@nvidia-desktop:~$ echo 414 > /sys/class/gpio/export
nvidia@nvidia-desktop:~$

Change GPIO direction

The GPIO direction decides if the GPIO should be used as Input or Output

Keep in mind that some Carrierboards are using unidirectional level shifters -> In this case only one direction will work properly.

More Information about such implementations are documented in the corresponding manual of your Carrierboard.

Syntax

jetpack 4.6 <=

change direction

echo <in|out> > /sys/class/gpio/gpio<GPIO_NR>/direction

Jetpack 5.0 >=

Change direction

echo <in|out> > /sys/class/gpio/gpio<GPIO_NAME>/direction

External driven extender

Change direction

echo <in|out> > /sys/class/gpio/gpio<GPIO_NR>/direction

Configure as Input

set GPIO direction as input

nvidia@nvidia-desktop:~$ echo in > /sys/class/gpio/gpio414/direction
nvidia@nvidia-desktop:~$

Configure as Output

set GPIO direction as output

nvidia@nvidia-desktop:~$ echo out > /sys/class/gpio/gpio414/direction
nvidia@nvidia-desktop:~$

Set GPIO Value

The logical GPIO level can be configure in the following ways. Keep in mind that its required to configure the GPIO as output before changing its output value.

Syntax

jetpack 4.6 <=

change direction

echo <0|1> > /sys/class/gpio/gpio<GPIO_NR>/value

Jetpack 5.0 >=

Change direction

echo <0|1> > /sys/class/gpio/gpio<GPIO_NAME>/value

External driven extender

Change direction

echo <0|1> > /sys/class/gpio/gpio<GPIO_NR>/value

Set low

Set output as logical low

nvidia@nvidia-desktop:~$ echo 0 > /sys/class/gpio/gpio414/value
nvidia@nvidia-desktop:~$

Set high

Set output as logical high

nvidia@nvidia-desktop:~$ echo 1 > /sys/class/gpio/gpio414/value
nvidia@nvidia-desktop:~$

Read GPIO state

Syntax

jetpack 4.6 <=

change direction

cat /sys/class/gpio/gpio<GPIO_NR>/value

Jetpack 5.0 >=

Change direction

cat /sys/class/gpio/gpio<GPIO_NAME>/value

External driven extender

Change direction

cat /sys/class/gpio/gpio<GPIO_NR>/value

The following example reads the current state of the GPIO. This operation works in output as well as in input mode.

read GPIO state

nvidia@nvidia-desktop:~$ cat /sys/class/gpio/gpio414/value
0
nvidia@nvidia-desktop:~$ cat /sys/class/gpio/gpio414/value
1