ODroid as raplacement for Raspberry Pi

I've been trying to get the LinuxCNC UI running since yesterday with no luck.

HAL threads flatly refuse to run on tobetter's 5.15 kernel. All of the userland tools like halcmd work fine though.

They will run on the 5.10 kernel, but none of the various UIs will load due to some error that mentions panfrost. So I'm guessing there's a graphics driver issue.

Next I'm going to take a step back and use tobetter's old 5.10 RT kernel on Ubuntu 20.10 like in this thread:

forum.odroid.com/viewtopic.php?t=41129

I'm also going to post my findings to the Odroid forum at some point.

Alan, I Installed your kernel to an eMMC drive but it booted in text mode to a command prompt
I tried tasksel but it failed so I unstalled ubunto mate. But It reverted to a non RT kernel somehow. 
But the CNC folder existed in the menus. I guess I should have just run xstart.

James has a good scripted version of Linuxcnc on the 5.10 kernel which might save you some time.
github.com/joco-nz/lcnc-bullseye-installer

> I guess I should have just run xstart.

I should have included that in the script. I'm going to run in kiosk mode, so I didn't bother installing a desktop

> James has a good scripted version of Linuxcnc on the 5.10 kernel which might save you some time.

Thanks. I've mostly been doing this as a learning experience, so I started from scratch. However now I'm running up against issues with tobetter's kernels which are above my pay grade to fix. Now I'm moving on from building it myself.

Speaking of which, I've just gotten the LinuxCNC simulator working on Debian Bullseye with realtime 6.0 kernel provided by meveric on the Odroid forums. Latency numbers look similar to the image and kernel from tobetter.

The conversation about it is here:

forum.odroid.com/viewtopic.php?p=365377#p365377

I've updated my repo that I linked to with instructions if anyone else is interested.

Alan, Great work. My Armbian mentor Going has  said to me tonight

Good afternoon, Rod. I found the problem. It is located in the kernel scheduler. Either the RT patch breaks something there or the developers haven't finished something. I had to disable some items in the kernel configuration file and now it works on my banana device. The tests work and show the expected results.
Now I'm launching an assembly for your device.

He's been amazing helping me. He was a bit rusty as he's been working on Xeomai 4 and had not played with PREEMPT_RT since 2015
We are working with the 6.2 kernel. I think I'll have to send him a N2+  if he nails this. If we get a RT branch, we can work on a linuxcnc branch

> We are working with the 6.2 kernel.

Glad to hear you're making progress. It will be awesome having this in Armbian.

If you can get me an address, I'll order him a an N2+ and an eMMC today. Should make her debugging process that much faster if he has one on hand.

Alan, In the absence of private massages, can you contact me here?
www.vmn.com.au/contact

Contact initiated

alangibson wrote:

Contact initiated

Replied. That page has been used quite a bit for linuxcnc stuff!

We got an early result!
The PREEMPT_RT kernel has been kept seperate from the image as its quicker to just build the kernel at this stage when trying
Go to my drive
drive.google.com/drive/folders/1yZJ1_14W...CekVJOER?usp=sharing
download the image and install it to an SD card (not eMMC at this stage) with Balena Etcher
Download and install the 4 debs with: sudo dpkg -i kernel-name.deb
Install linuxcnc with:
sudo apt install linuxcnc-uspace linuxcnc-uspace-dev mesaflash

Optionally play with isolcpus as thats not optimised yet.
Edit /boot/armbianEnv.txt
Enter: extraargs=isolcpus=2,3,4,5

Let us know how you got on

We've progressed with this. Added back wifi after a few warnings from my mentor about increased latency. Anyway, does not seem to have been much of an impact.
Finally got the N2+ connected to a MEsa 7i76e!
Ping times are very goodIts possible this can be improved as Armbian is using a generic NIC driver but its not a high priority.

I got a couple of latency errors and smart serial overuns with QTplasmac
But when I investigated with htop which shows cpu utilisation by core, these are only happening when one core on the CPU sometimes briefly hits 100 CPU utilisation on startup.
These errors do not happen with axis.
This confirms my belief I've had for a while that the modern GUIS are adding additional load on the CPU which exacerbates latency in modern kernels. So all in all, this is a useable board as long as you don't browse internet when cutting a part.