Build a custom gpio-keys pinmux configuration for the kernel

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

Hi there,
I would like to create a custom gpio-keys configuration to enable :

  • 7 analog GPIO inputs
  • 2 PWM GPIO outputs
  • 4 analog GPIO outputs
    Is that possible with the Jetson Xavier platform ?
    Much regards, Xavier.
2

Yes, It’s possible.
But you need to add A/D and D/A for your analog input/output.

3

Dear @juns,

regarding the gpio-keys configuration, I would like to test the correct configuration with PWM outputs but so far no success to output a PWM signal. Some informations about the current set-up :

  • I want to use “pin-13 (PWM01), pin-15 (GPIO27_PWM2), pin-18 (GPIO35_PWM3) of Xavier J30 GPIO”

  • Using Jetpack 4.3 (R32.3.1) by default (not new cfg/dtsi in place)

  • Running jetson-gpio/samples/simple_pwm.py on either one of the 3 PWM pins I see the 3V3 output going down for a few ms and then up to 3V3

  • pin configuration at runtime :
    cat /sys/kernel/debug/tegra_pinctrl_reg | grep pwm Bank: 0 Reg: 0x0243d030 Val: 0x00000450 -> gp_pwm3_px3 Bank: 0 Reg: 0x0243d038 Val: 0x00000450 -> gp_pwm2_px2

  • pwm configuration from the sysfs values :
    cat /sys/kernel/debug/pwm platform/39c0000.tachometer, 1 PWM device pwm-0 (generic_pwm_tachomet): requested period: 0 ns duty: 0 ns polarity: normal platform/32f0000.pwm, 1 PWM device pwm-0 (sysfs ): requested period: 0 ns duty: 0 ns polarity: normal platform/32c0000.pwm, 1 PWM device pwm-0 (sysfs ): requested enabled period: 10000 ns duty: 5000 ns polarity: normal platform/c340000.pwm, 1 PWM device pwm-0 (pwm-fan ): requested enabled period: 45334 ns duty: 0 ns polarity: normal platform/3280000.pwm, 1 PWM device pwm-0 (sysfs ): requested enabled period: 10000 ns duty: 5000 ns polarity: normal

I have the feeling the 3 PWM pins are PWM-enabled but I may not do right control ?
Best regards,
Xavier.

4

HI xavier,

What is your current problem? Could you help info you pasted? It seems every line is stuck together.

5

BTW, I don’t see anything related to gpio-keys in your question. Such topic should call “pinmux” instead of “gpio-keys”.

6

Dear @WayneWWW
my current issue to validate/check that the 3 PWM pins are in PWM mode and that I can control them with a simple test code to start with. Running Jetpack 4.3 without any cfg/dtsi modification so far so the J30 pins are in the default mode of Jetpack 4.3
Cheers,
Xavier.

7

Hi,

How is the current status? You have to check whether current pinctrl is pwm or not. If it is not PWM, then you could use jetson-io tool to configure it to pwm. Actually, jetson-io update the DTB as well.

8
  • How do you check the current pinctrl is pwm or not ?
  • jetson-io tool is installed by default in Jetpack4.3 ?

BR. Xavier.

9

Hi Xavier,

I would suggest you to use jetson-io directly.

Please check this page.
https://docs.nvidia.com/jetson/l4t/index.html#page/Tegra%2520Linux%2520Driver%2520Package%2520Development%2520Guide%2Fhw_setup_jetson_io.html

10

Hi @WayneWWW,

I have been using jetson_io to configure pin13(pwm8), pin15(pwm1), pin18(pwn5) and after reboot the tool confirmed that the 3 pins are in pwm mode.
Now I am lost about how to use this pins in shell/python script as I have the following sysfs mapping :

/sys/class/pwm$ tree . ├── pwmchip0 -> ../../devices/3280000.pwm/pwm/pwmchip0 ├── pwmchip1 -> ../../devices/c340000.pwm/pwm/pwmchip1 ├── pwmchip2 -> ../../devices/32c0000.pwm/pwm/pwmchip2 ├── pwmchip3 -> ../../devices/32f0000.pwm/pwm/pwmchip3 └── pwmchip4 -> ../../devices/39c0000.tachometer/pwm/pwmchip4

I have been trying jetson-gpio/samples/simple_pwm.py but no success and it seems this script is deconfiguring the pins ?

BR. Xavier.

11

Hi,

Please try the linux pwm node to see if you could see the pwm signal.

cd 32X0000.pwm/pwm/pwmchipY
echo 0 > export
cd pwm0
echo 200000 > period
echo 100000 > duty_cycle
echo 1 > enable

12

Hi @WayneWWW,
Thanks. Your test does work and the address/pin mapping is actually :

  • /sys/devices/32f0000.pwm/pwm/pwmchip3/pwm0 : J30/pin13
  • /sys/devices/3280000.pwm/pwm/pwmchip0/pwm0 : J30/pin15
  • /sys/devices/32c0000.pwm/pwm/pwmchip2/pwm0 : J30/pin18

Can I use a python gpio library to drive those PWM signals ?
I would like to use i2c/uart signals to talk to a 5V devices, I definitely need a level shifter to adapt the fast signals to 5V levels ?
BR. Xavier.

13

Actually I am wondering why simple_pwm.py is not working…
Need to investigate it on my side.

Can I use a python gpio library to drive those PWM signals ?

Is it an acceptable solution for you that we fix simple_pwm.py ?

14

Dear @WayneWWW,
yes if simple_pwm.py is fixed then it will a good base for me to work on the target feature. I am willing to help if needed (code/test).
BR. Xavier.

15

Dear @WayneWWW
may you have updates on the correction of the simple_pwm.py script ?
I would love to use the pwm pins from a python library.
Much regards, Xavier.

19

Hi xavier,

It seems the NX version has been updated on the github page.
Please refer to:
[0] GitHub - NVIDIA/jetson-gpio: A Python library that enables the use of Jetson's GPIOs
[1] Add support for Jetson NX · NVIDIA/jetson-gpio@ccaa362 · GitHub