Adding a physical feed hold button

I’d like to add a physical feed hold button that I can mount near the e-stop. I’m having trouble identifying whether the ESS has spare input/output pins that I can utilize. My confusion stems from the fact that some of the pins are also sent over via ribbon cable to the relay board.

It seems that if there are spare pins, I can then map a specific pin in Mach 4 to trigger the feed hold. Has anyone done anything with spare pins that can provide some help?

This will help you a bunch:
https://www.avidcnc.com/support/instructions/electronics/pnp/manual/21.2/schematics/
Here are some snippets from that:

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Thanks for linking the schematic. This looks like I can use any of the 8 inputs with their associated grounds. Is that correct?

Are the existing inductive sensors, relays, probe, and e-stop utilizing separate inputs than those listed in terminals 1-16?

If you read through the schematic, you can see where all the I/O is mapped and connected. There is more to that table. I just took a snippet of it.

I read through the whole page and I think I understand it. I’m just looking for confirmation if anyone is familiar

I suppose I should be able to review the Mach 4 configuration to confirm this too.

They should be available. All the existing inputs go through a custom breakout board and use different ESS pins.

As far as I can tell they’re not inputs in the traditional sense. You need to pull the 12V pin to ground. Either use a relay or a open collector IC or transistor. BTW even if Avid calls it a schematic it isn’t. That would require a lot more detail that so far Avid hasn’t released.

@eyesonlybob Are you using all the M12 ports on the CNC control box? Most people aren’t using A sensor or AUX2. The simplest path is to go that route, and the ESS pins for Mach4 configuration are right here Schematics - CNC Controller Technical Manual.