Mesa 7i92 Read Errors

Hi tommylight,
The issue happens with and without the drives are energized.
Furthermore, I already disconnected both cards from the 7i92 and the issue persisted.

And while you are correct in the DYN-4 being connected to an analog signal from the 7i77 with velocity mode since I have linear scales on 2 axes, with the 3rd axes being controlled via Step/Direction from the 7i85, the drives are not enabled due to the mesa card losing communication well before I enable them.

Do you have another PC to test with?
If not, find a USB cable, cut the small header, wire the Red and Black wires to Mesa 7i92 5V power connector and insert it into a USB port on that same PC with nothing else connected to Mesa 7i92 but power and ethernet. Mind the polarity.

1. What is your servo thread period?
2. Have you checked the tmax values when running LinuxcNC?

halcmd show param *.tmax

To interpret these values, the CPU frequency is also needed.
(at the tmax values are in CPU clocks)

I should mention that you can eliminate power supply issues
(and throw suspicion on timing issues) if  the /INIT light is
illuminated on the 7I92 after you get a read error.

 

Hi PCW,
Thank you for the points to look at.

I just tested the read and write tmaxes and they jump up to 1ms for some cycles, with my servo thread cycle time being 1ms as well.
Also the INIT light stays on after the error ocurrs, confirming that it is a timing issue on the ethernet interface.
I’m currently in the process of chasing down why it it jumps up sometimes.

Hi PCW,
We identified the issue in the ethernet driver. The linux kernel driver has some issues, and the RealTek driver works better.
Though there is an issue with setting the rx-usecs and tx-usecs values, causing the read/write times to be higher than we expected.
Thank you again for your support.

I have had some motherboards with Intel Ethernet hardware that were OK up to 4 KHz
With Intel MACs on corporate desktop PCs you may also have to disable AMT.
(and this may be impossible on some machines)