Usage of index signal only from encoders with 7i76e

Hi guys,

I am currently playing around with a machine which uses 5 steppers with encoders.
The original control only used the encoder index signals for referencing (besides 5 limit switches).
Do you think it's possible to use the index signal in the same way using a 7i76e?
Homes against the limit switch, then uses the index signal for precise home position.

The 7i76e only has one "real" encoder possibility, therefore I'd need to use the field I/O for the index signals.

Regards
Daniel

I think its possible but probably requires a hal component to simulate index behaviour.
(Latching the pulse and having tri-state output). You might be able to use the software
encoder component to provide that simple logic. The search for index move needs to be
slow enough that you are guaranteed to sample the index at the servo thread rate.
 

I'd drive it slow enough so the index will be seen, for sure.

Then the comp could either just reset the index-enable and I could link the index signal directly to the IO pin, or I could read the index and latch it until next index-enable comes. Either way, should work.

Thanks again PCW.

Forgot one detail, you must use this option:

HOME_INDEX_NO_ENCODER_RESET

Since the step position feedback will not be cleared on index

This also requires using LinuxCNC master AFAIK

Thank you. I am getting old... you know why? Once upon a time I wrote a component (attached), which just switches the input during the normal homing sequence. Had used it with a stepper + index pulse (sensor at a pulley) setup. Should be pretty reusable.
If not I will switch back to your suggestion.

Regards,
Daniel