Gravograph Engraving Machine(s) Conversion (Updated)

Dear All,

Figured it out with extended reading - thanks for this great forum! - and a bit of creative try-and-error.
All 3 axes are set up and calibrated, homing works like a charm
Next and last open issue is the spindle - but I don't expect much difficulty with that. Otherwise there'll be another post here ...

ORIGINAL POST:
I've started a project to convert a 30-year-old engraving machine (Gravograph UNICA) to LinuxCNC running on a Raspberry PI 4 with a MESA 7C80. I have several Gravograph machines of various sizes available and am looking to roll out my conversion to most of them, if it works out as planned. These machines may be old, but as such they're solid and reliable. Also they are simple as there's just one stepper and one limit switch per axis and the spindle motor to control. The main reason for conversion is that the UNICA machine only runs on it's own Gravograph-unique operating system with a tiny monochrome CRT screen and propietary keyboard, with no communication port. The other, larger machines can communicate via serial port, but they also require Gravograph-only software ...

So far, I got the Raspberry PI, 7C80 and LinuxCNC up and running to the point that the x-axis stepper is operational by using linuxcnc.hal and linuxcnc.ini from this thread:
forum.linuxcnc.org/42-deutsch/52725-3-ac...esa-7c80-und-raspi-4

As far as I can tell, there's no wizard available (stepconf etc.) for configuring the MESA 7C80, so I need to work with the config files directly(?)

I modified linuxcnc.ini so that the stepper runs smoothly, and added three lines for the limit switch and homing. The stepper now starts running when I home the machine in LinuxCNC, and the program is apparently waiting for the limit switch to be triggered.
This is where I'm currently insecure and would like to ask for assistance:

• What terminals to connect the limit switch to at the 7C80?
• How to set it up as a NC contact (Switch opens when x-axis home position is reached)?
• How to set up homing to move the spindle towards home at first if the home switch is not triggered, and then move a short distance away and back to the final home position? 
  
  This is my current linuxcnc.ini:
   

  File Attachment:

  File Name: linuxcnc.ini
  File Size:4 KB
  
   
  Thank you for reading and thanks in advance for any answers!
  
  Best regards,
  Erik 
  captain-panda