ODroid as raplacement for Raspberry Pi

> You have to be careful when doing stress testing. The test needs to look like the load you expect to have for the numbers to be relevant.

We have little control over how the applications and drivers are developed so we look for worst case in testing. If you wish to gamble on what the lowest latency might be to run a base thread for software stepping on your hobby machine that is up to you. There is no latency police enforcing anything involved here

If any of the ODroids end up testing reliable enough to use in production machines they will be be running servo threads anyway with external FPGAs for steppers, encoders and servos.

Bari wrote:

If any of the ODroids end up testing reliable enough to use in production machines they will be be running servo threads anyway with external FPGAs for steppers, encoders and servos.

I don't think there is any doubt Odroid's  are reliable as I've used several of their  x86 devices and they work fine once you get the NIC drivers installed. (Hint: the 5.10 kernel -  Bullseye and above includes the driver). One of them runs Bullseye and Ethercat. Its just their user base is not really worried about Real time so we are not catered for.

You see ignorant comments like this one whxih was well retorted!
forum.armbian.com/topic/13250-preempt-rt...omment&comment=96666
  Some people have no idea. 20 ms is real time what crap!
Nice reply
With the Odroid N2, you get a 6 core CPU (4 BIG, 2 little for power saving)

I think if you look at kernel development both normal and real time, there is a lot of effort happening to support the ARM environment, some of it is directed at the N2. You can't use this stuff on the Buster 4.x kernel......

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