: If you have a floating head with a switch to detect the material top use a G38 straight probe to locate the material top prior to touching off the torch. To use a probe you have to "hook it up" using hal to motion.probe-input.
:You can choose any input-mode parallel port pin--10, 11, 12, 13, or 15.
:connect it in your hal file with a line like
: net probe parport.0.pin-10-in => motion.probe-input
:If the signal is inverted (starts at 5V when probe is not in contact, goes to 0V when the probe makes contact), then use the inverted version of the pin:
: net probe parport.0.pin-10-in-not => motion.probe-input