One more HURCO BMC 20P Retrofit

Leave the wiring as is.
The only thing needed is wiring each switch to Mesa inputs while leaving everything as is.
The homing will need a bit of tuning though, to find the max speed for home_search_velocity as not to exceed the switch to much. Setting low homing speed initially is essential, for all homing related moves.
This way you have the limits in LinuxCNC and in the drives.

These are mechanical, specifically "Honewell AS-J215" limit switches.
Since I have dismantled all the previous controls, at the moment I do not have a way of knowing whether voltage was passing through.
But you gave me an idea, if I could power them up externally to see if I press them if voltage changes.

The picture looks like they have used a normal 25 pin DB25 to connect to a break out terminal board. I would expect 7 & 10 would be +24v and -24V.
If thats the case, half the pins may be commoned internally and the other half will be used for the limit switch signals. Eg say your pin 2 (or 16) would be commoned to 7 or 10.

As always thanks for everyone’s input.

Things were simpler than initially thought…
Basically the limit switches have three contacts, one for power (com), one for normally open and one for normally close. My idea is to use them as NO, give them 24V and return the pins (the signal) to the inputs of 7i77.
My query remains though, giving them “unlimited” 24V (just connect them to the PSU) and expect to return back to the 7i77, am I in danger of smoking the card?
Is there a limit of how much voltage/current the 7i77 can accept on inputs?How it’s usually done?  Is it ok, to send 24V from the 7i77 (from an output but it will be always on) and get the signal back to one of the inputs?

christos wrote:

Is it ok, to send 24V from the 7i77 (from an output but it will be always on) and get the signal back to one of the inputs?

Yes. From the 7i77 manual, the inputs have a nominal 20 kΩ input impedance (well, technically the manual says 20 kelvin-ohms, but I think it's obvious what is meant. ). I cannot find anything in the manual about maximum current (and therefore voltage) that the inputs can handle, but the manual gives several examples of using them with 24 V.

You can connect directly from a 24V power supply to 7I77 inputs
(the 7I77 inputs will take -36V to +36V indefinitely)

If you have a high current 24V supply you should fuse appropriately
to protect the wiring in the event of a short.