Network communication fail

Dear community,

even if this is my first post, I would like to thank you in advance because I love your
posts which were very helpful for me.

I would also like to take this opportunity to thank you for the docu, which very is detailed.
(I sometimes have problems to understand straight away how it is meant, but until now I
got everything working.)
Thanks!

Now to my problem. I retrofitted a CNC lathe with LinuxCNC.
I used a Raspberry PI 4 as a computer with a MESA 7i95. Unfortunately the mesa card goes into error and this happens quite often
resulting in a red light on the mesa card and a "Joint following error" comes along.

Despite the configuration, I am a beginner with Linux and I have no idea how to find out where the problem is, do you have any tips or solutions for me?
Thank you in advance.

PS: Do you know more about the Mesa company? I have a friend who now also would like to build a CNC machine
and I would like to upgrade a milling machine with LinuxCNC.
Unfortunately, the Cards are sold out in Europe for over a year. Can they be bought anywhere else?

PPS: Sorry if the english is hard to understand but my english is so bad
that I always have it translated by a translator.

I'd try turning off wifi, if it's on.

Thank you for your quick answering.

It seems like the errors depend on the operation. I will document them in more detail if they occur again.
The Mesa is powered by a 5V 6A power supply independent of the RPI.
Yes, the encoders are wired to the Mesa 7i95.
Yes, the Mesa connects directly to the RPI.
Yes, I get a latency warning on startup.
(Which I blamed on the Python program I wrote.)
Yes, the error usually occurs when the machine is working and the spindle is therefore running.

And yes, WiFi is active. Because that's how I copy the CNC programs to the RPI.
(is that a problem? And with what command is it properly disabled
and can I turn it on/off to copy over without having to reboot?)

Latency warning is a bad sign. What kernel do you use? do you have isol_cpus on kernel cmdline? (cat /proc/cmdline) -- run latency tests and make sure those are OK. Also, check power supply and check for undervoltage messages, and heatsink the CPU.

A red LED indicates a watchdog bite so usually this is a latency issue, not power related.
(power failure during operation would clear the watchdog fault so no red LED)

Are you using isolcpus=1,2,3? This is usually required with a RPI

What does a ping test show?

sudo chrt 99 ping -i .001 -q 10.10.10.10


( let run for a few minutes then hit control C )

( This assumes you have the 7I95 card  IP address set at 10.10.10.10 )

​​​​​​This thread has nothing to do with EtherCAT.
I wonder if the mods could move it to a more appropriate section.

Sorry for setting up the thread in the wrong section.

-CPU is acitvely cooled by 2 fans
-(cat /proc/cmdline) gives isolcpus=3 as a result
-sudo chrt 99 ping -i .001 -q... gives "bad timing interval"
-simple ping test shows time=0.202ms - 0.101ms
-latency-test shows 1032230ns 

Linux version 4.19.71-rt24-v7l+ (andypugh@linuxcnc) 
(gcc version 8.3.0 (Raspbian 8.3.0-6+rpi1)) 
#1 SMP PREEMPT RT Fri Jan 1 21:15:16 GMT 2021

additional info: when RPI boots, I always have the message "CPU 0 not supported" 

Is it possible to support the RPI in some way to get better results?

What linuxcnc version so you run? Did you build from source? Can you post actual output of linuxcnc on the console?

latency-histogram --nobase should show less than 100000ns as worst case jitter (100µs).