Quickly redefine GPIOs on connector J21

Dear all,

On the dev kit TX2, I need 3 custom outputs, active low at boot. My choice is to use the following signals from J21

  • I2S0_CLK, GPIO3_PB.03, From pin G2, GPIO3_PJ.00 (PinMux), gpio no 392
  • I2S0_LRCLK, GPIO3_PB.00, From pin H1, GPIO3_PJ.03 (PinMux), gpio no 395
  • GPIO8/ALS_PROX_INT, GPIO3_PX.03, From pin H13, GPIO3_PI.04 (PinMux), gpio no 388

Actually, they are not defined as GPIOs and at boot these signals are generating clocks from the 15th to the 25th second. And each time we connect/disconnect ssh

The default pinmux.xlsm is not adapted for the dev kit TX2 (missing eth0). I am searching for a quick and easy solution to configure the 3 pin above.
The idea is to modify the original device tree in the kernel package and only running JetPack-L4T-3.0linux-x64.run without other installation but :

  1. tegra186-quill-p3310-1000-c03-00-bas.dtb and all .cfg files are always auto-generated before flashing the dev kit. Not possible to manually modify the .cfg files
    a) Where are the source files (device tree) which are generating the .dtb? And eventually the .cfg sources.
    b) And how to configure if the source file is not a .cfg?

  2. Another solution is to modify the .dtb directly on the dev kit after flashing by using the fdtdump fdtget fdtput from the device-tree-compiler
    a) But where to find the information/document to configure the 3 outputs above?

hello Thierry7,

please refer to the Jetson TX2 OEM Product Design Guide from the Embedded Download Center.

a) Where are the source files (device tree) which are generating the .dtb? And eventually the .cfg sources.
since you’re using TX2, you could download L4T 27.1 Sources here: http://developer.nvidia.com/embedded/dlc/l4t-sources-27-1

Hello Jerry,

Thank you for your quick reply.

Just one remark : Comparing the Jetson TX2 OEM Product Design Guide and Jetson-TX2-Generic-Customer-Pinmux-Template.xlsm, the Design Guide doesn’t mention all my outputs as GPIOs (usage/description column for G2+H1).

Do you have one answer to the point 2a) for pin G2,H1,H13 ?

My first idea is to only install JetPack-L4T and run the installer. Cancel the installation, change local files such device tree (or other) to redefine my outputs and re-run the installer flash process.
3a) Is this possible ? And how ? Loading the L4T 27.1 Sources and placing which files and where ?

This seems not an issue any more, see the discussion at https://devtalk.nvidia.com/default/topic/1014464/configure-gpio20-aud_int-and-gpio10-wifi_wake_ap-pins/

Hi, Thierry7

How did you calculate GPIO Number as 392 and 395 can tell me the formula to calculate it

I have done calcultaion using the following link and my GPIO numbers were wrong and the calculation you have done is correct