I’ve read pretty much every topic on this issue, so I’m posting to get specific info on this topic.
I’m using Jetson Nano with a carrier board from a vendor called Auvidea and it’s interfaced via UART connector to STM32 MCU for communication purposes. Everything was fine on one of their earlier version boards since I had access to ttyTHS1 port that was tunnelled from Jetson to UART connector on the carrier board through on-board STM32 MCU.
Since they’ve updated their carrier board design (no revision notes whatsoever, and the customer support is zero) I only have access to ttyS0 port (the same connector I used before) that’s reserved for serial console and login info input and it’s working fine once the serial console does it’s thing and I login (of course, I had to change my Nano firmware to read from ttyS0), but that’s really not an option since it would require a modification of the external STM32 MCU firmware.
As I see it I have only two options; to permanently turn off serial console and login prompt on ttyS0 or to permanently switch serial console output and login prompt to some other UART that’s not needed for external communication. I’m pretty much a beginner with Linux so any help will be appreciated.
I am not sure I fully understood your ask, but if you want to disable then UART port, this can be done on the module directly, by disabling the pins on the pinmux. For doing that you need to download the pinmux spreadsheet directly from the Jetson Download Center, change the neccesary pins, generate the dtsi files, replace them on the kernel sources and rebuild the kernel image. Once this is done you need to replace the generated DTB in the L4T BSP package and reflash your device.
I want to disable serial console on ttyS0, but use it after the Linux boots as a regular UART port. I’ve achieved this with the following command:
systemctl mask serial-getty@ttyS0.service
After that, I no longer have login prompt on ttyS0, and I can use it as a regular UART after boot. In addition, I have to silence the UART port from the outside STM32 for 10-15 seconds until the Jetson boots so it doesn’t prevent autoboot.
Does that make sense to you or am I missing something? I realize it’s a hacky solution, but I have no support from the carrier board vendor nor would I like to change anything dramatically in the STM32’s firmware.