Step/Dir servos + Encoders = follow errors... and so much pain.....

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08 Feb 2021 17:36 #198026 by jhandel
for Piggy backing are you thinking something around tweaks to hostmot2sp6.vhd & hostmot2.vhd... Specifically something around this line

StepGenIndex(conv_integer(ThePinDesc(i)(23 downto 16))) <= IOBits(i);

maybe something there routing the MuxedQCountIDXPin into StepGenIndex() if present?

Is that what you were thinking PCW?

Could be flipped on the UseStepgenIndex flag.. like if UseStepgenIndex then use the current routing then add a UseMuxQCountIndex flag and if that is set to true then look out for the MuxedQCountIDXPin to route to StepGenIndex() ?

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08 Feb 2021 17:57 #198030 by PCW
I was thinking of added of adding 2 pin types, a muxed stepgen-index and a
muxed shared encoder index and stepgen index and doing the required pin connection
hackery to support both (with the constraint that the shared pin stepgen and muxed encoder
have to be the same instance)

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08 Feb 2021 17:59 #198031 by jhandel
Oh that is smarter and less hacky than my idea :-)... Like it :-)

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22 Feb 2021 14:57 #199715 by jhandel
I "found" 5 inputs so I am moving things around to free those up..

Quick question, I have double ended encoder signals, how should i feed those into a 7I75? Should I just read off the positive side or do I put the neg against ground too?

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22 Feb 2021 16:01 #199717 by andypugh
You would probably get best results with a differential transceiver.
Or with a Mesa card that is equipped with differential inputs. (but those are more expensive)

I would see what PCW suggests for straight wiring connections, though.

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22 Feb 2021 16:09 #199719 by jhandel
Yah, trying not to buy a 4th Mesa Card for 5 signals.. I already have a 7i76e, 7i75 and 7i89.. Especially given how this feature has to be written in firmware I am not sure I can hang another input off of the RS422 port..

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22 Feb 2021 16:22 #199720 by andypugh

Yah, trying not to buy a 4th Mesa Card for 5 signals.. I already have a 7i76e, 7i75 and 7i89


If you have a 7i89, why are you connecting the the encoders to the 7i75?

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22 Feb 2021 16:27 - 22 Feb 2021 16:46 #199721 by jhandel
Because PCW wrote a new feature that works with inputs as Index Pulse so you can use index pulse with homing of a step-gen motor..

However, it doesn't work with Multiplexed encoder ports (all of the encoders on 7i76 and 7i89 are multiplexed)...

PCW is working on that firmware update too (because he is awesome)... But if I can start testing the rest of his great work in 2.9 using normal inputs its a win for everyone..

To do that, I need to route my index pulse signals down to these 7i75 pins and flash the firmware to treat them as the new StepGen Index pulse inputs...
Last edit: 22 Feb 2021 16:46 by jhandel.

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22 Feb 2021 17:06 #199724 by jhandel
Here is a picture of the signal I am dealing with.. I think this reads like the neg on the signal is coming from Common so maybe its ok? or its dropping to box ground which is not the same as common...
Attachments:

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22 Feb 2021 17:16 - 22 Feb 2021 17:17 #199726 by PCW
For a single ended input, you would just use ground and the OA+, OB+, OZ+ outputs
(leaving the OA-,OB-, and OZ- pins unconnected)

If you ground the OA-, OB-, and OZ pins you are shorting out the differential driver chip
and could damage the drive
Last edit: 22 Feb 2021 17:17 by PCW.

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