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I am using a Dell AIO PC OptiPlex 3050 and it has a
Realtek RTL8111HSD-CG Ethernet LAN 10/100/1000M on system board for connection to the Mesa 7i76e
I worked well with the Bulleye's version of LinuxCNC before I switched to 19.4.

Just when I was about to give up and just risk working with the swapped servos, the second servo now shows the same symptoms when running on the bad channel .

So it looks like it is the 7i76e that broke and not the servos .

Plus, that card seems to be still not in stock anywhere in the EU. Already had that problem when searching for one two years ago.

At least I am only using 4 of the 5 channels, so was able to reconfigure the machine the unused channel instead, hopefully I'll find a new card, soon.

Thanks a lot for all your help, PCW!

No 5V driver can supply 5V to a load (it will always have some internal resistance)
You might check the drive input resistance between STEP+ and STEP-
when unconnected. If both drives match then its likely that 7I76E S/D
outputs have been damaged.

Note, when checking the S/D outputs, its  much better to measure both
the STEP+ and STEP-  pins individually relative to ground

Did you swap the motor connections at the 7I76E or the motor?

If differential signalling is used and you have either:

A bad cable
A bad 7I76E step output
A bad motor driver step input

You can get flaky behavior if just one on the differential
signals is working.

I get it! Its a big machine so you do need wireless. But you should not consider  USB.
I would look at this pendant which has a 433 Mhz receiver and designed for industrial use. Pair it with an external antenna at the receiver end.
www.wixhc.cn/product/433mhz-manual-pulse-generator
Unfortunately, you still end up with those 20 odd wires but they are contained in the control box.
These work really well with a Mesa card that has  a MPG input built in (eg 7i76e etc). For Ethercat, you would need an encoder input which are pretty costly. Note the Estop is  dual circuit so designed to work with a safety relay.
There is a fair bit of custom hal code to get these going.

Note Ethercat adds an additional layer of complexity to a linuxcnc build and it was hard work when I built my machine. But it is a lot eaiser today with efforts from myself, Scott Laird and others...

I've noticed that the Omron encoders are available in NPN, PNP and linedriver versions.

I wasn't sure which type that was most suitable for use with Mesa cards but after using a few different search criterias on Google to search through this forum I found this excellent post by PCW which cleared things up:

forum.linuxcnc.org/30-cnc-machines/48587...on-mesa-7i76e#267477

So it seems I'll be ordering a Omron rotary encoder with a 5 volt linedriver interface.

One a side note I also found this page on the Omron website which clarifies the max cable length for the different versions of the encoders:

www.ia.omron.com/support/faq/answer/34/faq00969/index.html

I have a Mesa 7i76e and a couple of thcads available in Brisbane.
Contact me here www.vmn.com.au/contact
and advise you have on this thread.

I would change the 5V power supply powering the Mesa 7i76E board, find a really good one.

Have you configured the arc voltage input on the 7i76e tb2/th3 page? With that setup then you should come to a mesa thcad page where you can enter the scaling values from the back of your thcad10. It's all done in pncconf.

I would not just use one core but you can use isolcpus
so LinuxCNC uses only one processor (the last one
so if you have a 4 core machine isolcpus=3)

When you say USB card I would be suspicious if its not
a plug-in dongle (try testing with the cards disconnected)

I've got a USB wireless card in there to access the internet from the linuxcnc machine.

I'm using Debian 12 and it seems as if irqbalance is missing on that one. So I'm unable to setup the service the way it's shown.

Would it be bad if I just set in the bios to use 1 core? would this help? When the machine is running, it's not like I'm using anything in the background.

Is there a wireless card in the 3020? These are often the cause of network latency.
(USB WIFI dongles seem OK)

I have a similar vintage HP 8300 USDT (I5 3470S 2.9 GHz)
running cheerfully at 4 KHz.  (with the IRQ pinning trick)


 

Here's the latency and ping times 

Here's the bios for this dell optiplex 3020.


I have about 5-6 of these dell boxes of different machines/specs and running the latency tests, this one came out on top. Most of the newer ones that are better spec'd preform worse on the latency tests.

i'm gonna read through IRQ affinity post later today. And see if I can get a readout of all the hardware including what network controller is in this box.

thanks pcw, setting the feedback works, but I can't understand why when I reset the axis with G10 L20 P0 A0, the value of A does not go to zero but remains at a small value which seems to be a delta from the absolute coordinates.