Problem homing with index

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17 Mar 2022 11:45 #237529 by HalaszAttila
If i use 2.9.0 or recompile the hostmot2 driver, must i update firmware in 7i92 FPGA?

As PCW mentioned in previous message:
"There is new firmware and support in LinuxCNC 2.9
for homing to index on pure step/dir systems if you want to try
it."

If yes, where can i find this firmware?

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17 Mar 2022 15:20 #237533 by PCW
Replied by PCW on topic Problem homing with index
What hardware do you have?

LinuxCNC standard homing to index with a stepgen requires
firmware that include these features as standard bitfiles do not
have these features.
The following user(s) said Thank You: HalaszAttila

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17 Mar 2022 20:00 #237560 by HalaszAttila
7i92 + 7i76 (on DB25 connector) + 7i85 (on ribbon cable) + 7i84

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18 Mar 2022 17:12 - 18 Mar 2022 17:13 #237653 by PCW
Replied by PCW on topic Problem homing with index
Here is a 7I92+7I76+7I85 bitfile with stepgens that have index capability:

Encoders 0..3 are on the 7I85 and share encoder index's  with stepgen index's 0..3
encoder 4 is on the 7I76 and has no stepgen index (just encoder index)

 

File Attachment:

File Name: 7i92_7i76_...sdid.zip
File Size:126 KB
Attachments:
Last edit: 18 Mar 2022 17:13 by PCW.
The following user(s) said Thank You: HalaszAttila

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23 Aug 2022 15:35 - 23 Aug 2022 15:36 #250262 by turbostew
Replied by turbostew on topic Problem homing with index
I too have an issue with index homing on my Bridgeport.  I spent years engineering closed loop controls so not a stranger to servos configs but not a LCNC expert. I have a 7i92 with 7i85.  I am running servos sending step and dir to servo drives (drives close their own loop).  I then send the encoder feedback to the pids in position mode with FF0 set to 1.0 and a 0.5 Pgain (set to 0 doesn't really fix anything) to help following error at speed along with limiting the error to 0.005".  I am getting 0.0003" following error (not counting machine slop) with this setup.  When I look at feed back and command after homing they may be 0.100" off....  When I rehome, it seems to get worse each time...

What exactly do I have to do to get rid of the big encoder to position discrepancy using index homing?
Grab the firmware from above post?
Do I have to run in Vel mode?  I don't want to....
What is this business of sharing encoder indexes?  Can someone spoon feed it to me?
An example ini and hal with this setup?

Thanks for the Help,
Kent
 
Last edit: 23 Aug 2022 15:36 by turbostew.

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23 Aug 2022 15:56 #250267 by PCW
Replied by PCW on topic Problem homing with index
For step/dir drives with encoder feedback, you need to use the
stepgen in velocity mode. The pncconf and mesact setup utilities
do this automatically.

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23 Aug 2022 16:17 #250269 by turbostew
Replied by turbostew on topic Problem homing with index
Thanks great LCNC wizard... Do I use the posted bit files?

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23 Aug 2022 16:28 - 23 Aug 2022 19:40 #250270 by PCW
Replied by PCW on topic Problem homing with index
No, those are for homing to index in pure stepgen systems (no encoder feedback)

In this case (no encoder feedback) the stepgen hardware needs to behave like the
encoder index hardware, that is, it must latch and zero the stepgen position
(in hardware) at external index occurrence when stepgen index enable is true.
Last edit: 23 Aug 2022 19:40 by PCW. Reason: clarify

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