Float switch code

Hello friends, I am trying to build a oxyfuel cutting machine.
Now, unlike plasma machines using PlasmaC, I am trying to use sheetcam generated codes that gives complete custom control of Z axis. Also I have deceided using capacitive THC using thc components if linuxcnc.

But I am stuck with float switch. I will use 200mm range contact optical digital output sensor so that nozzle do not touch plates.

but how to enable that with sofware? what code i should use in Gcode file?

Ypu can try a gcode approach using a touchoff.ngc file similar to this on from JT
gnipsel.com/shop/plasma/files/touchoff.ngc

It is a digital output , NO+NC available.

I mean float switch is digital output. Capacitive THC gives analog voltage output.

That I am not sure right now.

If it is beyond THCAD range i have plan to use voltage divider. I have THCAD 5 in my stock.

Will update as soon as i get the values.

I have never used subroutine before.

Request for practical guide how to use that. 

subroutine in gcode file or a separate file??

The intent was the touchoff was called in our gcode when the cutting should start. You normally pass it some variables. Time to read up on  gcode subroutines.