Ubuntu 12.04 x86 Kernel with RTAI 5?

Hi,

did anyone manage to get a combination of RTAI 5 and LinuxCNC 2.7.4 running? it is stated in the changelog that it supports RTAI 5, but it will fail to start with the message "only kernel 3.4.9.... is supported".

That is somehow annoying since i can choose between a running machine or a functional touch-screen monitor as the packed kernel seems to lack support of my touchscreen device... the screen is working with my custom build 3.16... kernel with RTAI 5, but then i'm not able to start LInuxCNC.

I don't like to change to jessie and wheezy has the same issue since it looks like its using a kernel build with the same parameters.

I'm very open to any suggestions
Thanks!

Hi,

thanks for the reply.
Since it uses the same stone-age-kernel (3.4-9), this would be no step forward.

Have you tried any of the preempt-rt kernel patches? Maybe you can get one of them to work with your hardware.

As Todd says, Preempt-RT is probably your best bet if you want an up-to-date kernel
(as new as 4.4.7 currently)

Depending on your specific hardware, Preempt-RT can have mediocre to very good latency

i'll give it a shot.
since i have mesa-cards, it shouldn't be a problem if latency increases a little

Very rough Mesa card / LinucCNC/ average motion control timing needs:
< 50 usec jitter OK for all sample configs
< 200 usec jitter OK for configs with servo or PID steggen hal setup
< 600 usec jitter OK for configs with servo or PID stepgen hal setup +DPLL firmware

(assuming 1 KHz servo thread)

Machines with slow acceleration may be OK with a 500 Hz servo thread allowing
these times to double

Machines with very high acceleration (say > 1 G) and high accuracy may
require a faster servo thread

I have analog servo-controllers and approx. 600mm/min maximum feed.
Lets see if I get a newer kernel to work, otherwise having no touch input is something i have to live with:)

well, finally some success:
preemt-RT 4.6 kernel is working with my touchscreen!
latency increased from ~ 25µs to about 110µs -> servo-thread reduced from 5kHz to 2kHz

Despite from that, everthing is working gmoccapy with touchscreen is far better ^^
One unexpected side-effect: no sporadic latency spikes anymore