Catching the index pulse with a 7i76

Will I be able to catch the index pulse of an encoder on the GPIO input of a 7i76 card>?
I want to use it to home my 4th axis with.

Probably not with GPIO unless the encoder is quite low resolution,
is moving very slowly or both. The 7I76 encoder input will work however.
Another option if the 7I76 encoder input is already used is to use the second
encoder input on the 5I25s P2 (assuming the standard 7I76x2 firmware, there
are a second set of TTL compatible encoder inputs available on P2)

I quickly scanned the manual and could not see the pinout definition for the second port. Well at least not the detail as far as signals are concerned or are they just IO to be configured as I please?

There is no firmware specific pinout information in the manual
since there are nearly limitless firmware options.

If you download the 5i25 zip file and look in the configs/hostmot2
directory you will see a file named 7i76x2.pin. This has the pinout
of the 7I76x2 config normally used with the 5i25/7I76 card set.

You may already have these pin files installed in
/lib/firmware/hm2/5i25 if you installed the pncconf xml files

Another option is to turn on the hostmot2 debugging options
related to pins and modules (man hostmot2)
This will write a _lot_ of pinout info to the kernel log when
Linuxcnc starts

Peter
Ok got that. I see the second port looks after the rest of the Step/Dir channels. Is there a way that these can all be assigned to GPIO type pins? I would very much like to drive some custom boards with that port if possible. Then I don't have to use parports at all .

Sure, just don't enable more than 5 stepgens (or more than 2 serial ports)

Like all hostmot2 configurations, if a secondary function like PWM, step/dir, SPI, encoder
etc is not used, the pins revert to GPIO use

That is really great news, thanks a lot.
So if I enable the second encoder it will automatically assign the correct pins, as I saw it in the 7i76x2 file, to the encoder?

Yes assuming that you do have a 7i76x2 config in your 5I25
(it will be unless you changed it). You can always verify by
enabling 2 encoders and checking the dmesg pinout list

Thanks Peter. I loaded the 7i76x2 firmware when I got the cards.