Ian, USBCNC is configured much simpler than this, all that is needed to be done is place a limit switch at the Home of each axis. then in the software you tel it how much travel each axis has (effective table size) once this is done each time you Launce the software it will ask you to reference the machine, depending on what order you configure each axis, it will slowly move the axis up to the switch and then back off until it see continuity of that switch again. mine is set to reference Z then Y then X. once this is done the switches then act like e-stops, so (if) soon as the axis is triggered the software will stop and disable the Stepper/Servo Drives and any other things like coolant pumps you may have setup.

Also unlike mach3 the switched have there own input so the software knows what switch has been activated.

Hope that helps

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