Odroid N2-Plus serial port not working

elsabz · April 23, 2023

Hello,

i need to activate the serial port on the odroid N2-plus, the serial port is on pins (J2 - 2x20 PINS) 8/10.

Usually this uart with ubuntu is at /dev/ttyS1. If I try to use it on armbian I get an input/output error.

I read the following post, I understand that it is not implemented yet.

Can anyone point me in the direction of trying to do this?

Igor · April 24, 2023

17 hours ago, elsabz said:

Usually this uart with ubuntu is at /dev/ttyS1

"Ubuntu" does not define interacting with the hardware, kernel does. As we don't use proprietary kernel from Hardkernel, this is done different, possibly its undeveloped feature. What you need to do is edit device tree and enable this UART (this is standard procedure on all boards). If overlays were made, then this is a lot easier: armbian-config -> hardware -> enable / disable, save, reboot.

elsabz · April 24, 2023

Hi @Igor thanks for the answer, the first thing I did is armbian-config: System -> Hardware -> uartA and uartB enabled, then reboot.
Unfortunately it doesn't work! With "ls /dev/tty*" I see all ports tty0-50, ttyS0-7, ttyAML0, any port gives me input/output error when I access it.

How can I edit device tree and enable this UART ? Where can I find the information?

usual user · April 24, 2023

11 hours ago, elsabz said:

Where can I find the information?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/serial/amlogic,meson-uart.yaml

elsabz · April 25, 2023

Thanks @usual user for the reply, ok I also saw this way of describing the hardware in the post I linked at the beginning. Unfortunately I'm new in armbian (I apologize but I'm ignorant), so please I ask you to follow me in the next description.

The following structure is located in the /boot folder:

/boot
-> dtb
 -> amlogic
  -> overlay

-> dtb-6.1.11-meson64
 -> amlogic
  -> overlay

In the amlogic folders (both in one path and in the other) there are several .dtb files.
Files named odroid-n2-plus are as follows:

meson-g12b-odroid-n2-plus.dtb
meson-g12b-odroid-n2-plus-spi.dtb

Where is it determined which file is to be used?
These files I can easily convert to dts and then compile dtb.

Which files should I edit?
In which path should I change them?

usual user · April 25, 2023

10 hours ago, elsabz said:

I'm new in armbian

Usually I use armbian barely. So I can't really say anything about the nature of hers implementation.

10 hours ago, elsabz said:

Where is it determined which file is to be used?

It's probably up to the user's decision. In terms of file name, it could follow a similar scheme to how I use it. Since the use of NOR flash has an influence on the usable eMMC speed, armbian probably also offers a variant with and without its support. I also use the DTB filename to express which features I've added. E.g. one of my DTB is: meson-g12b-odroid-n2-plus-con1-opp-uart.dtb with multiple overlays applied. This way I just need to replace the original DTB with the desired one, this works in any environment regardless of an overlay framework.

Werner · April 29, 2023

It is worth considering to upload smaller files simply via our forums here. Users might be distracted when being asked to download something from a more or less fishy 3rd party hosting provider.

usual user · April 29, 2023

The download link was only included because the file was already stored for another purpose and was intended to demonstrate a real-world example. The file could possibly be used for a quick test, but is not suitable for permanent integration into Armbian as is. I usually upload files that should remain available for Armbian in the long term in the forum. I always have my doubts about binary files, because their validity is not easy to verify, so I think the warning on the download page is just right. Since the file can only be found via the reference link, it is just as trustworthy as if it were deposited directly in the forum and the user should be aware of what he is getting.