Unable to access GPIO526 used for SPI0_CS0

Hi all,

I’m working with /dev/ttyTHS1 to make use of the High-Speed UART data transfers in JEtson Xavier NX.

  1. I’m able to test UART loopback by shot of TX-RX, but as I connect the RADAR AWR1843 for data transfers, I need to send RADAR configurations and receive a acknowledgement : “Done” that’s not happening thanks for any idea on this.

  2. The UART0 RESET pin is mapped to SPI0_CS0 at GPIO526 (320 + (25x8) + 6). I need to know how to access GPIO526 from kernel as /sys/kernel/debug/gpio gives me only upto 288-511 on gpiochip0.

Yash M J

Hi @linuxdev,

  1. I was able to dedicate /dev/ttyTHS1 for sending Radar Data(low pull-up Vlotage issue).
    But still accessing GPIO 526 on Xavier NX i.e., pin with Ball name : SOC_GPIO42 is a mystery.

  2. Also I have dedicated /dev/ttyTCU0 for receiving Radar Data, by disabling debugging console operations on the port by default.
    In this case I’m facing issue of board entering into Bootloader Shell Mode. Any information on this issue would be of great help.


Instructions for disabling serial console within earlier boot stages varies depending on device and release version. In some of the older releases you had to actually rebuild the bootloader with the option disabled. In many of the newer releases there is instead a parameter passed to those stages via device tree.

On a running Jetson you can see the device tree’s arguments for passing to various boot stages:
cat /proc/device-tree/chosen/bootargs

The early boot stages would see any “console=” or “earlycon=”. As boot reaches the point where the Linux kernel loads, you will see this for setting up actual Linux kernel command line arguments, found in “/boot/extlinux/extlinux.conf”:

APPEND ${cbootargs} ...

The macro “${cbootargs}” expands to the content from the device tree “chosen->bootargs” node, possibly after minor edits. Thus, changing the device tree should also change early boot stages, but changing extlinux.conf may change only the arguments to the Linux kernel itself.

I do not know which device tree contains this, but documentation on modifying the device tree and installing it would be how you can install a tree which does not pass serial console arguments in those earlier boot stages.

Btw, if someone could move this to the NX forums it would probably be a better location. I only saw this by accident.