mesa 7i76e + 7i85s homing problem on 4th axis index-enable

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21 Mar 2024 09:50 #296448 by Raban
Hi everyone and thanks in advance for your help...

I have just finished mechanically and electrically installing the fourth axis, moved by an Asda B servo.
The motor moves correctly in jog and the encoder pulses are read by the 7i85s board, A/A B/B Z/Z .
However, I cannot do homing using Z/Z of the encoder.
Index-enable is always at zero, but if I try to force it to 1 with the command sets xxx-index-enable 1 it goes to 1 and returns to zero when the Z/Z pulse passes, so I think there are no electrical problems .
I think the problem is the configuration on ini or hal, I'm attaching my files, they're still in progress, maybe you can tell me where I'm going wrong
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21 Mar 2024 11:23 #296460 by Raban
linuxcnc version 2.8.2

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21 Mar 2024 14:20 - 21 Mar 2024 14:22 #296471 by PCW
I suspect the basic issue is that you have no 'A' home switch and HOME_SEARCH_VEL is non zero.
If you want to home only on index, HOME_SEARCH_VEL should be 0 and the search for index
will be done at HOME_LATCH_VEL. Also I don't think HOME_FINAL_VEL can be 0.

linuxcnc.org/docs/html/config/ini-homing.html

An additional issue is that you do not have position feedback coming from the encoder
but rather the stepgen. This will not work for homing to index unless you use special firmware
with step/dir index. If you use encoder feedback you should lower the P term to about 10 to start.
 
Last edit: 21 Mar 2024 14:22 by PCW.

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21 Mar 2024 14:40 #296474 by Raban
thanks pcw,
-HOME_SEARCH_VEL is non zero.
and i don't have position feedback from encodet.

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21 Mar 2024 19:20 #296492 by Raban
thanks pcw, setting the feedback works, but I can't understand why when I reset the axis with G10 L20 P0 A0, the value of A does not go to zero but remains at a small value which seems to be a delta from the absolute coordinates.

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