Mesa 7i96s --USB error finishing read

Trying to integrate my vfd with linuxcnc I first went down the modbus rabbit hole ( Mesa 7i96s pktUAT on P1    Mesa 7i96s with 5 encoders and Modbus ) until I got the RS-485 fried.

So I decided to use AnalogVoltage for speed control and pins for direction and getting additional Data via USB this setup was going well (data beeing read from the USB got nicely read into axis interface with about 4Hz update rate.

until I tried to start the spindle ---> error finishing read!

consistent every time --> changed Power supply of the card : same
--> increased servo thread time: same

even without loading MB2HAL as soon as the USB to RS-485 Adapter is connected whenever I start the spindle ---> error finishing read! and I get nice system messages that a new USB-Device has been found.

as we had an power outage at the shop I can not yet supply what ETH adapter is used I just know the machine is an old HP laptop running Linuxcnc 2.9

 

checked cables:
vfd grounded;
motor wires shielded and grounded on both sides;
cables not running parallel to each other;
all that shenegans
moved the rs485 to usb adapter from inside the cabinet to the laptop side --

better --at least the messages of finding a new usb device have disapeared -- but still mesa7i96s.0:error finishing read!

This getting better seems to confirm that it is a EMV problem

next step would be to find an optical isolated adapter any other ideas?

Do you get the errors if the VFD is not powered?

No!

Well you could run the VFD entirely from 7I96S analog and 7I96S isolated outputs for enable and direction. That way there is no galvanic connection between the controller and the VFD circutry.

It does seem you have a very severe EMI issue (as evidenced by interference with Ethernet
and damage to the 7I96S RS-485 interface)

I would at the minimum add a line filter to the VFD input, and a common mode choke (large ferrite bead) to the UVW motor wires) or you may cause additional damage.

Well, I'm already (after all that experimenting with modbus) running the the machine from the analog and isolated outputs -- I was hoping to get additional feedback into linuxcnc -- somwhen next week an isolated rs485 adapter will arrive and I will try it that way.

Bur after having all this trouble maybe I should warn others about the EMI problems with the "SAKO SKI780" VFD

Up until now I was mostly using VFD's from SEW -- some EMI is to be expected but the interference this VFD is emmiting was unexpected.

Not sure if it will help much, but only connect your motor cable shield at the drive end. instead of both ends.