Using a rotary encoder for Homing A-Axis on 7i96s

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31 Jul 2025 06:03 #332584 by Gautham
Hi Everyone

I am in the process of wiring up my first CNC 5-axis machine and I wanted to know if I can use this Rotary Encoder  to home the A-axis and if so how would I wire it up. From the research I have done, my understanding is that it can be done but it involves some editing of VHD files that I didn't really understand since I am new to LinuxCNC. Thanks for the help

Gautham

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31 Jul 2025 12:06 #332596 by andypugh
it seems to be a conventional quadrature encoder, so it should be easy to integrate without any complex VHD changes, but this will depend on what interface hardware you are using.

You might find it better to home to a simple flag on the axis though, especially if you are using stepper motors and have no other feedback.

Also bear in mind that in many cases the orientation of the workpiece in the axis is not repeatable (for example for work held in a lathe chuck), and so homing isn't any help. My own A axis is set up to just home without moving, and then I touch-off the work orientation with a dial indicator or spirit level.

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31 Jul 2025 13:48 #332600 by PCW
If you are using the 7I96S, and its encoder interface is free,
you can setup homing to index, using encoder feedback.

If you do not want to use encoder feedback, you can use
7i96s_esdid1.bin firmware that supports homing  to index on
step/dir channel 0. Note that you don't need a full
encoder for this as only the index signal is used.

It either case, I would assume you have the encoder with index
on the motor and the home switch on the A axis.

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