Mesa 7i92 Read Error

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31 Jul 2019 14:05 #141008 by PCW
Replied by PCW on topic Mesa 7i92 Read Error
That actually sounds like a different type of error (bad KSZ8851?) Since the OP
had the same read error with a different 7I92 card. I Also ran his original card for 72 hours without a dropped packet and did tests at -51C(Freeze mist) and 100C without
issue which tend to rule out a marginal chip

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31 Jul 2019 15:58 #141012 by Qenf
Replied by Qenf on topic Mesa 7i92 Read Error
I thought all the boards were testing before shipping and the defective chip would be detected. I noticed that the error appears either immediately after the activation of the interface or after a sufficiently long time. There may be some incompatibility of interfaces.

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31 Jul 2019 16:33 - 31 Jul 2019 16:39 #141014 by PCW
Replied by PCW on topic Mesa 7i92 Read Error
Yes, all cards are initialized and loopback tested over Ethernet but subtle problems
may be undetected (even by factory testing of the chips)

A good example of a similar issue is flash EEPROM chips, occasionally you get ones that
leak and forget their programming after a couple months, manufacturers do not test for
this flaw on a chip by chip basis and we see these every once in a while.
Last edit: 31 Jul 2019 16:39 by PCW.

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16 Aug 2019 13:44 #142318 by 10K
Replied by 10K on topic Mesa 7i92 Read Error
I FOUND THE PROBLEM!!

I was never sure where the communication problem came from - the specific computer I was using, the Linux installation and configuration, LinuxCNC itself, the hardware in the controller box, electromagnetic interference, power supplies, etc, etc.

With the help provided, I was finally able to track it down to the ethernet cable. Specifically, it was a short cable that ran between a panel mounted female RJ-45 to the 7i92 inside of the controller enclosure. I replaced the main ethernet cable with a shielded version a couple of years ago. I didn't replace the short cable, because it was very hard to get to, and many other cables had connectors that were too long to work, due to the enclosure layout. I was also thinking that I might be getting electromagnetic interference outside the metal enclosure, but that the inside cable was already shielded. This short cable had a sharp bend in it right at the 7i92 card. The bend must have resulted in a broken wire that was making a fairly good but not a great connection, and would fail after literally millions of reads over an extended period. That's what made it so hard to find.

I pulled the short cable out of the enclosure, but still included it in the middle of a string of three ethernet cables. It worked with no errors over a 24 hour period when it was not bent. I found that if I bent the cable right at the connection, I could cause the read error immediately.

I've ordered another short cable, but with a built-in 90 degree plug. I'm thinking this will permanently fix my problem.

Because of the extremely intermittent nature of the problem, it took several years and countless hours to find it. It is probably the hardest problem I've ever had to debug. On the good side, I now have extensive knowledge about LInux and LinuxCNC.

Many thanks to all who posted things to try over the years, and special thanks to PCW.
The following user(s) said Thank You: Clive S

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16 Aug 2019 14:03 #142319 by pl7i92
Replied by pl7i92 on topic Mesa 7i92 Read Error
i did also face multiple times problems on the 7i92
that disapeard on realy good cable use not the cheep "china" stuff you can get for 1USD

real good cables from the next Telecomunication or TV-store
there are double shielded cat-6 out
en.wikipedia.org/wiki/Category:Ethernet_cables

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