Remora - ethernet NVEM / EC300 / EC500 cnc board

Hi LabQuest,

That error message is normal and nothing to worry about. It's because we are not using the base thread, only the servo thread in LinuxCNC.

I understand, thank you Scotta.

Hello again,
I'm struggling with the infamous following error when I try to go faster than about 2300mm/min.
I'm running my steppers at 1000 steps/mm as is required by my application.
I've read through this topic and the stepper tuning doc but I can't seem to figured it out.
Does my servo thread latency matters ?
I'm still running the default configs beside the JOINT SCALE set to 1000.

I was also thinking that this issue could be due to the default signal timing being to long for remora to keep up.
How and where do I configure the stepgen timing with remora ?
See the attached timing requirements for my drivers.
 

The latency is already high after such a short amount of time without running glxgears, so the latency might be the cause if it goes higher during operation. Isolating all cores makes no sense, you should always have one available for the system to run its tasks on. It won't hurt to try to find better settings in the bios and kernel parameters.
Network latency can also be a cause, pinning the Ethernet irq to the isolated core can help.

Yeah, I was running a youtube video in the background but still, you're right, it's quite high.
I thought that this could be a possible cause so I've already made all of the recommended changes to the bios.
Thank you for the heads up on the core isolation, I must have misunderstood Talla83's video.
I will try to better understand kernel settings, unfortunately, there's isn't a lot of information about my dell optiplex 3020m.
Pinging the EC500 gives a latency between 0.130 and 0.25ms.

I'm trying to narrow down the possible causes, do you experience about the same ethernet latency as I do ?

EDIT: Using Halshow I can get so more debug information:

• remora.read.time is between 5 to 700 000
• remora.update-freq.time is between 4-700
• remora.write.time is 5 to 800 000

The ping latency seems to be good, mine (with mesa) gives 0.2ms. If your latency won't get higher after a longer time of testing it should be good enough.
You could try to increase the servo_period to 2000000

With an Optiplex 3040m I had good results with these parameters:
isolcpus=3 intel_pstate=disable processor.max_cstate=0 idle=poll cpufreq.default_governor=performance i915.enable_dc=0 ahci.mobile_lpm_policy=1 irqaffinity=0 nomodeset quiet

From 1x8gb to 2x2gb (of the same brand/speed) for dual channel also improved the latency
forum.linuxcnc.org/18-computer/39371-res...cnc?start=330#271127

In your case it should be isolcpus=1

If the error still appears it might be helpfull to upload your ini file.

Does this look ok to get the encoder PV1 counting? PV1 should be the MPG socket. I don't know if I have a hardware issue or code issue. Also does the nvmpg.so need to be compiled first? I'm using an adum1200 to bypass the opticouplers. PV1 does not count when I move the encoder in Halshow

Looks like I can rule out network latency, good.
The pc was supplied with 1x4gb, I'll try to swap it out for a dual channel combo.

Well, all hope isn't lost, thank you Royka, I'll try to move forward with the recommendation you've provided !

I borrowed an old pc with a very low latency of about 3-4us (still steady after 1300sec)
Unfortunately, I'm not getting any improvement, I'm still getting a following error above 2300mm/min (~38KHz)

There must be another limiting factor somewhere else, how can I improve my troubleshooting method ?
Did anyone achieve a step rate higher than 38KHz with a similar setup ?

As Royka suggested, I've tried to increase the servo period, without success. (Though, lowering it definitely makes things worse)
Also, how can I make sure that the default stepper timing are correct ?

Attached to this post, you'll find my config.

In the last line of "remora-eth-3.0.h" from the remora component the default line is:
#define PRU_BASEFREQ 40000 // Base freq of the PRU stepgen in Hz

Try to increase that frequency and recompile/install

And a quote of Scott: "Your joint max velocity needs to he higher than the overall max velocity so that a joint can try to catch up the following error."