Enable UART(0) on Orin NX

[r.vries]

Hey,

How do i go about enabling UART on the Orin NX?
Ive flashed the Orin NX using these steps:
${L4T_RELEASE_PACKAGE} = Jetson_Linux_R35.2.1_aarch64.tbz2
${SAMPLE_FS_PACKAGE} = Tegra_Linux_Sample-Root-Filesystem_R35.2.1_aarch64.tbz2
And these steps: Quick Start — Jetson Linux Developer Guide documentation
However when testing the UART I get a permission denied?
-bash: /dev/ttyTHS0: Permission denied
-bash: /dev/ttyTHS3: Permission denied
-bash: /dev/ttyTHS4: Permission denied
How do I fix this?
Ive seen this post Enabling the correct UARTs on the Orin NX
But I cant find the steps to “enable” the UART?
Ive checked the pinmux sheet and for my usecase I want to use UB3, to which THS does this translate?

Thanks!

[r.vries]

Ive fixed the permission denied by adding my user to the dialout group. But when trying THS0, 3 and 4 these do not appear to be connected to UART0. How can I use UART0?

[r.vries]

So I understand now that UART A D and E are enabled on the Orin.
How do I switch D or E to B?

[r.vries]

I have found the file tegra234-p3767-0000-p3509-a02.dtb that contains the uart settings
However when I change to okay
serial@3110000 { status = "okay"; };
and turn UART D to disabled
serial@3130000 { status = "diabled"; };
Then I recompile the dts to dtb file. But when I check the file again after the flashing. this is reversed… Also the Orin still only has A D E enabled.
How do I fix this?

[KevinFFF]

Hi r.vries,

What’s your carrier board for Orin NX?

Please refer to the following thread about the UART usage in Orin NX.
OrinNX : How to check UART is working? - Jetson & Embedded Systems / Jetson Orin NX - NVIDIA Developer Forums

May I know what’s your use case for UART?

[r.vries]

Hi Kevin,
I am using a custom carrier board.
The link you provided does not really help, I have UART B exposed and I want to use it for communication to another device. I checked the pinmux sheet and I dont think I need to change anything there?
Ive tried enabling it in the dtb file but this gets reverted.
I have a feeling that something else is overwriting this during the flashing process.

[r.vries]

This is currently the pinmux sheet, no changes from the original

[akhil.veeraghanta]

how are you testing the uart? that error looks like you are trying to run /dev/ttyTHS0 which won’t work

can you post the output of sudo dmesg | grep tty

and how are you editing the dtb file, if its getting reverted you are possiblying using a different one than whats being flashed?

[r.vries]

Hi, ive found the issue. I was changing the dtb file in /bootloader but I should have changed it in /kernel/dtb