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 So is there a bug in the PREEMPT_RT support in the 6.12 kernel, or is it simply not implemented the way LinuxCNC has come to expect? Obviously LinuxCNC needs to support a working standard.

This conversation is a bit confusing because rodw and I are doing different things to get the same result.

I am starting with Raspberry Pi OS, switching to their 6.12 branch then building the kernel to enable PREEMPT_RT. I'm doing this because they don't have a kernel build of 6.12 with realtime enabled yet.

rodw is starring with plain Debian and using a build system to create an image for the Raspberry Pi.

Sidenote: all realtime code is merged in upstream 6.12 now, but you still have to enable it at build time with a configuration option. There's no way to turn realtime on and off after it's built. 

These are Linux kernel patches, so I guess where the kernel devs hangout.

Hello,

Got the drive working again today, the parameters for Control Mode and Pulse Type were indeed wrong (so you were both right

Turns out that my backup parameters file was not good at all, I ended up just copying the working parameters from one of the X drives to the new Y drive. Both axis have the same mechanical setup, gear reduction ratio etc...

@ihavenofish : you are right, these drives have CAN bus capability. I made this choice at the time as I was not quite clear about the various options. Now, I wish I had chosen the E version that offers EtherCat...

I'm thinking about upgrading the whole setup to EtherCat, possibly running LinuxCNC from a RaspBerry. Pi. That would allow me to get rid of the PC/Parallel Port limitations, move all the hardware inside the control cabinet, and have more I/O to finally add some extras to the machine.

Thank you all for your help, great to see this community thriving !

Is there a GitHub tracking thread (or something else) for those patches?

I would be really interested in following that thread.

hahaha

These things happen.

We're making some headway towards getting a 6.12 kernel going with rod's image builder.
But despite what the recent skuttlebutt suggests for arm platforms it seems that some patches are still required for realtime.

I have made a mistake. I thought the kit I bought gave no *physical^ access to the SD card. But, it does.
My apologies for the trouble and misunderstanding.

Tom

I just installed linuxcnc on my desktop PC  using the Debian trixie alpha1 ISO on an AMD64 PC
Linuxcnc 2.3 is included in the trixie repositories
It installed fine and brought in the PREEMPT_RT kernel.
Linuxcnc started Using POSIX realtime with no further action

So it looks like its a Raspberry Pi thing which is resolved by applying the kernel patches. I'll try tonight