Linuxcnc with Teknic SST-1500-UCX

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01 Oct 2020 20:51 #184510 by spacemanspiffee
Alright,

So it's been a few days and I finally got a few hours and the right connectors and things to start getting things wired up with the 7i76e.

I have 24v going to the mesa board according to the wiring guide that Norbert created: forum.linuxcnc.org/27-driver-boards/3191...76e-connection-sheet

I have an ethernet cable running directly from the computer to the mesa card.

I installed LinuxCNC on my machine, updated to the latest version from the master (2.9 I believe).
I set up a static IP on the computer of 10.10.10.12 and on the mesa of 10.10.10.10 and set the jumper W3 to match.
I can ping the board in the terminal and get response times in the range of 0.15.
I can run the mesaflash tool and everything looks good on that front as well.

I ran pncconf to just set things up super basic and get linuxcnc talking to the 7i76e. I set up a basic 3 axis configuration and assigned the stepgen to the propper pins on the board.

Here's the issue I'm running into. When I launch Linuxcnc, immediately it pops up an error: Unexpected realtime delay on task 0 with period XXXXX.
I tried fiddling with a couple things, one of which is the actual servo period setting. Whatever I set this number to is the number that I get for XXXXX when linuxcnc errors.

I've run the jitter test and am getting results in the 85000 range, so not great but could be workable for use with the ethernet mesa card as far as I can gather.

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01 Oct 2020 21:20 #184513 by PCW
What value are you using for servo period? normally 1000000 ns (1 ms) is used


Also If you have a Intel Ethernet chip on your hardware, you will need to
disable IRQ coalescing as mentioned in the hm2_eth manual page.

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02 Oct 2020 03:20 - 02 Oct 2020 05:04 #184529 by spacemanspiffee
Turns out I was missing a zero in the servo period. I had 100000.

I upped it to 1000000 and have my motor turning! Thanks for the suggestion.

Is there a quick way to tell whether I have an Intel Ethernet chip? Edit: found it, I've got a broadcom chip
Last edit: 02 Oct 2020 05:04 by spacemanspiffee.

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02 Oct 2020 05:08 #184535 by spacemanspiffee
Alright. I've got a motor turning and I pulled the step/unit number from the wincnc ini file and copied that into my linuxcnc setup. Only tested the x axis distance so far, but it looks at the very least in the ballpark.

Currently the motors are hooked up with basically loose wires that I crimped into a molex connector so that I didn't have to cut anything apart while working on it. Should I be concerned about shielding the wires that go from the mesa to the servo drives?

I've got to get the 7i89 set up next so I can get the encoders looped back into linuxcnc.

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02 Oct 2020 08:01 #184541 by tommylight
I would use shielded cables on anything with low level signaling, it saves a lot of headache later on.

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02 Oct 2020 14:18 #184576 by spacemanspiffee
What are some best practices for doing shielded cables? Do I tie the shielding in with ground?

I've got molex connectors going into the servo drives. Is that an issue for doing a shielded cable?

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02 Oct 2020 17:22 #184589 by tommylight

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07 Oct 2020 18:31 #185290 by spacemanspiffee
I think I've got the basics. Thanks for the links. I have some shielded ethernet cable that I'm planning to use for all my connections from the mesa board to the servo drives. How necessary is the star grounding point on the chassis of the machine and the grounding rod? This isn't a plasma table so I don't have nearly the noise generation as a system like that.

I think one of my next steps is to get the 7i89 into the equation talking with the 7i96 and linuxcnc.

Do I need a specific bitfile to configure these guys to interface with eachother? I didn't see a bitfile that had this combination in the support files that I downloaded from the mesa website.

In a more general sense, I'd love just a bit of a 10000 foot view of what the bitfile does.

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08 Oct 2020 04:41 #185329 by PCW
To use the 7I89 with a 7I76E you would need to use the 7i76e_7i76x1_7i89x1d.bit bitfile
Bitfiles are the firmware that is loaded into the FPGA to configure it for specific
hardware interfaces.

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