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MachPro Input Mapping for Tool Setter and Probe

Purpose

This document tells you how to map (assign) a physical input to a MachPro probing signal for:

  • a tool setter (tool length measurement switch or plate)

  • a probe (part probe, touch plate, or ohmic probe)

MachPro uses Mach4 signal names and Mach4 probing G-code.

Definitions

  • CNC: Computer Numerical Control.

  • I/O: Input/Output.

  • Tool setter: A device that triggers when the tool touches it. MachPro uses it to measure tool length.

  • Probe: A device or circuit that triggers when it touches the part (or a probe plate). MachPro uses it to find part edges, tops, and features.

  • Input signal: A software “name” for an input state (active or inactive) in MachPro/Mach4.

  • Pin / input pin: A physical digital input on your motion controller or breakout board.

  • Pin alias: A user-defined label for a pin. It makes mapping easier to read.

  • Active-low / active-high: The electrical logic level that the software treats as “active.” Many plugins let you set this per input.

Safety

  • Keep the Emergency Stop (E-stop) circuit available and tested before you do probe moves.

  • Make sure the probe signal is inactive before you start a probing move. If the probe signal is active at the start of a G31 move, Mach4 can treat the probe as already “hit” and continue without moving as you expect.

Tutorial

Quick check: confirm the signal changes

  1. Open Diagnostics (or Machine Diagnostics) in MachPro.

  2. Find the probe status indicator for the probe signal you plan to use (for example, Probe or Probe 1).

  3. Trigger the device by hand:

    • touch the tool setter

    • short the probe plate circuit (if you use an ohmic/touch plate)

  4. Make sure the correct indicator changes state (active/inactive). Mach4 screens typically show probe state in diagnostics.

If the indicator does not change, do the mapping steps in the next sections.

How-to

Map the tool setter input

Use this when the tool setter is the input that triggers the tool length routine.

  1. Go to Configure > Control > Input Signals.

  2. Select the probe signal you will use for the tool setter:

    • Probe (used by G31 / G31.0), or

    • Probe 1, Probe 2, Probe 3 (used by G31.1, G31.2, G31.3).

  3. Enable the selected probe signal.

  4. Map the selected probe signal to the physical input:

    • Select a Pin Alias (recommended), or

    • Select a Port/Pin (if your system uses that method).

  5. Set the correct active state (active-low or active-high) for that input.

  6. Save the configuration.

  7. Test the mapping in Diagnostics:

    • Manually trigger the tool setter.

    • Make sure the correct probe indicator changes state.

Notes

  • Many MachPro installations map the tool setter contact input to Probe 1 so the main probe can stay on Probe. If you do this, your tool setter routine must use G31.1 (or must be configured to use Probe 1 in the wizard or macro).

Map the tool setter overtravel (limit) input

Use this when your tool setter has a second switch for overtravel (fault protection).

  1. Wire the overtravel switch to a separate digital input.

  2. Go to Configure > Control > Input Signals.

  3. Map the overtravel input to a limit or fault signal that your system uses for protection (for example, a Z negative limit signal).

  4. Test the overtravel switch:

    • Trigger it by hand (only if it is safe).

    • Make sure MachPro shows the limit/fault state.

  5. Keep the overtravel signal separate from the probe signal. A common setup is:

    • main tool setter switch → probe signal

    • overtravel switch → Z-- limit (or a dedicated fault input)

Map a probe input

Use this when the probe is a separate device from the tool setter (for example, a 3D probe).

  1. Decide which probe signal you will use:

    • Probe (G31 / G31.0)

    • Probe 1 (G31.1)

    • Probe 2 (G31.2)

    • Probe 3 (G31.3)

  2. Go to Configure > Control > Input Signals.

  3. Enable the selected probe signal.

  4. Map it to the correct physical input pin (use a pin alias if available).

  5. Set active-low or active-high correctly.

  6. Test in Diagnostics:

    • Trigger the probe.

    • Confirm the correct probe indicator changes state.

Reference

Probe signal to G-code mapping

Probe signal name in MachPro/Mach4Probing G-code
ProbeG31 or G31.0
Probe 1G31.1
Probe 2G31.2
Probe 3G31.3

Where to map signals

  • Motion plugin pin setup (example: set pin direction, active-low/high, alias, and noise filtering).

  • MachPro/Mach4 Input Signals (enable the signal and map it to the pin alias).

Common problems and causes

  • Probe indicator is always active:

    • wrong active-low/high setting

    • wiring is reversed (NO vs NC)

    • probe circuit is shorted

    • probe signal is mapped to the wrong input

  • Probing routine fails to start or gives wrong results:

    • probe signal is not mapped in Input Signals

    • wrong probe code selected (G31 vs G31.1, etc.)

  • False triggers (noise):

    • add noise filtering/debounce in the plugin (if available)

    • use shielded cable and correct grounding

Explanation

MachPro reads physical inputs from your motion controller. Each input must be mapped to a software signal so MachPro can use it.

Tool setters and probes both use the Mach4 probing system. That is why they map to probe signals (Probe, Probe 1, Probe 2, Probe 3). The probing G-code selects which probe signal MachPro watches during the move (G31, G31.1, and so on).

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