Touch probe inquiry

#1

Hello,

I have a pocket nc v2-10 with the latest kinetic control (just upgraded last weekend (10/24/25)).

I saw Josh Pieper tutorial on his touch probe and got excited to add one. I noticed that he had to create a splitter (I haven’t gone through his whole project yet) and was wondering if there was a cleaner method. It seems like the staff was ok with this (I did see the warning about the limit switch effecting the calibration) so I wanted to ask if they could provide clarification on a way to access a pin for this probe input.

I have been learning about Linux cnc a little and see that it uses a parallel port (and a breakout board) from what I saw on my pocket nc that seems to be the hat the beagle board is connected to. Is there a way to pull out a connector from there and keep it close to the current inputs (Ethernet/usb) on the front? I was wondering if the electrical schematic is available too.

I am a noob at cnc and have some software and electrical experience so will prob get some of this wrong as I learn about it!

Thanks for your input here.
Guy

Oh one more thing, I read on another post that kinetic control has to support the probe inputs too. I think it was working a little (z axis?) but might run into issues with this later.

11/2/25 update
I took a pic of the BBB and daughter board. This showed me the free pins (assuming they are actually free!). P9 GPIO_20 (pin 41) looks free (would love some verification here ;)).

I bought a BBB and made an image of the sd card to run it with. I have the Kinetic control working but it looks like halcmd is failing since there is no hardware to talk to (again assuming since I don’t know this side of things :()

free pins
free pins1684×749 363 KB

11/3/25 update

***Work in Progress Use at Own Risk***

Guide to Adding a Stock Probe to PocketNC on Pin P9_41

This guide provides a clear, step-by-step process to add a stock probe to your PocketNC on pin P9_41 (STOCK_PROBE_PIN=941), integrating it with LinuxCNC and ensuring proper signal inversion for an active-high probe. The process involves physically connecting the probe, configuring the INI and HAL files, and creating a G-code subroutine for probing. Tested as of November 3, 2025, 11:49 PM EST.

Prerequisites

  • PocketNC running LinuxCNC with Pentamachine’s Kenetics interface.
  • A stock probe (active-high, TRUE when triggered) with a 5V to 3.3V level converter.
  • Administrative access to run sudo commands (pocketnc user has this).

Step-by-Step Instructions

1. Physically Connect the Stock Probe

Connect the stock probe to the BeagleBone Black:

  • Hardware Setup:
    • Attach the probe’s signal line to GPIO_20 (pin 41, P9_41) on the BeagleBone Black.
      • I did this by using breadboard wire
    • Use a 5V to 3.3V level converter to ensure compatibility with the BeagleBone’s 3.3V logic.
    • Connect the probe’s power and ground lines as per its specifications (typically 5V power, ground to BeagleBone GND).
  • Verification: Ensure the probe outputs a 3.3V signal (from level converter) when triggered (test with a multimeter if needed).
  • Images:
    image1
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    Pin 41 for probe signal and Pin 43/45 for ground

image0
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currently testing with a 5v/3.3v breadboard powersupply and a voltage converter to input 3.3v to beaglebone board (I assume everyone knows 5v will fry it!!!)

2. Overcome Read-Only Filesystem Access to update/generate files

The /usr filesystem (containing /opt/pocketnc/) may be read-only due to OSTree. Temporarily bind it to a writable location:

sudo mkdir -p /tmp/settings
sudo mount --bind /usr/opt/settings /tmp/settings
sudo mount -o remount,rw /tmp/settings

Once done with the file editing, clean up the mount (or reboot)

sudo umount /tmp/settings
  • Note: This is a working solution to the filesystem configuration. I am not sure if there is better ways to do this (both mounting to gain access and unmounting/reboot afterwards). Please advise!

3. Add STOCK_PROBE_PIN to Base INI

Ensure the pin is defined in the configuration:

sudo nano /opt/pocketnc/Settings/versions/v2revR/PocketNC.ini
  • Modify: Add to [POCKETNC_PINS] section (below the INTERLOCK_OPEN_PIN):
STOCK_PROBE_PIN=941
  • Save: Ctrl+O, Enter, Ctrl+X.
  • Purpose: Defines pin 941 for the stock probe.

4. Create v2_stock_probe Feature Files

Set up the HAL file, HAL inclusion, and signal mapping:

sudo mkdir -p /opt/pocketnc/Settings/features/v2_stock_probe
sudo nano /opt/pocketnc/Settings/features/v2_stock_probe/v2_stock_probe.hal
  • Content for v2_stock_probe.hal:
    # Stock Probe - ball is 0.0780"/1.98mm
newinst bb_gpio stock-probe-pin pin=[POCKETNC_PINS]STOCK_PROBE_PIN direction=input
setp stock-probe-pin.invert 1
unlinkp probe-inputs.in-2
net probe-input-0 probe-inputs.in-2
  • Save: Ctrl+O, Enter, Ctrl+X.
sudo nano /opt/pocketnc/Settings/features/v2_stock_probe/append.inc
  • Content:
    [HAL]
HALFILE=/opt/pocketnc/Settings/features/v2_stock_probe/v2_stock_probe.hal
  • Save: Ctrl+O, Enter, Ctrl+X.
sudo nano /opt/pocketnc/Settings/features/v2_stock_probe/overlay.inc
  • Content:
    [PENTA]
STOCK_PROBE_SIG=probe-input-0
  • Save: Ctrl+O, Enter, Ctrl+X.
sudo chown pocketnc:pocketnc /opt/pocketnc/Settings/features/v2_stock_probe/*
sudo chmod 644 /opt/pocketnc/Settings/features/v2_stock_probe/*
  • Purpose: Configures pin 941 as stock-probe-pin, inverts the signal, and maps it to probe-input-0.

5. Enable Feature in Base INI 

sudo nano /opt/pocketnc/Settings/versions/v2revR/PocketNC.ini
  • Modify: Add to [PENTA_FEATURES] section:
    V2_STOCK_PROBE=1
  • Save: Ctrl+O, Enter, Ctrl+X.
  • Purpose: Instructs generateINI.py to include v2_stock_probe.hal.

6. Restart services

Use the Kinetic Control UI - Config → Machine Config: Restart Services button

  • Purpose: Regenerates /var/opt/pocketnc/PocketNC.ini and reloads LinuxCNC.

7. Verify Pin and Signal 

halcmd show pin motion.probe-input
halcmd show sig | grep probe

Example sig output:
Probe NOT triggered

bit FALSE -- probe-input
                                 ==> motion.probe-input
                                 <== probe-inputs.out
bit FALSE -- probe-input-0
                                 ==> probe-inputs.in-2
                                 <== stock-probe-pin.in

With probe triggered

bit TRUE -- probe-input
                                 ==> motion.probe-input
                                 <== probe-inputs.out
bit TRUE -- probe-input-0
                                 ==> probe-inputs.in-2
                                 <== stock-probe-pin.in
  • Expected Output:
    • Pin: bit OUT FALSE stock-probe-pin.in (open) or TRUE (triggered).
    • Signal: bit FALSE probe-input-0 (open) or TRUE (triggered).
  • Purpose: Confirms pin 941 is active and toggles correctly.

8. Create G-Code Subroutine - ***Need to polish this. May work or may not depending on current coordinates…

echo -e "O<stock_probe> sub\nG91\nG38.2 Z-3 F5\n#<probe_z> = #5063\nG90\nG0 Z[#<probe_z> + 2]\nM2\nO<stock_probe> endsub" > /home/pocketnc/stock_probe.ngc
  • Purpose: Defines a subroutine to probe down, store the Z position, and retract.

9. Integrate Subroutine with Kenetics

To be tested and finalized. The G-code stock_probe.ngc must be added to Kenetics’ subroutine library:

  • Placeholder Steps:
    1. Copy /home/pocketnc/stock_probe.ngc to the Kenetics subroutine directory (e.g., /home/pocketnc/subroutines/ or /usr/opt/settings/subroutines, confirm path).
    2. Register the subroutine in Kenetics - subroutine can be called from web interface o<stock_probe> call (this may be enough?)
    3. Position the probe with enough room and have the probe in your hand to manually test.
  • Expected Behavior: Z-axis moves to the left, when probe triggers it stops, and retracts.

10. Verify G-Code File 

ls -l /home/pocketnc/stock_probe.ngc
  • Expected Output: -rw-r--r-- ... stock_probe.ngc.
  • Purpose: Confirms the G-code file exists.

Testing and Troubleshooting

  • Verify Files:
    ls -l /opt/pocketnc/Settings/features/v2_stock_probe/
    Expect: -rw-r--r-- pocketnc pocketnc for all files.
  • Check INI:
    grep STOCK_PROBE_SIG /var/opt/pocketnc/PocketNC.ini
    Expect: STOCK_PROBE_SIG=probe-input-0.
  • Debug Signal:
    halcmd show all | grep -E "stock-probe|probe-input-0"
    Look for: stock-probe-pin.in → stock-probe-raw → stock-probe-oneshot-or.out → probe-input-0.

This guide ensures a replicable process for adding a stock probe and manually testing. Probe routines and perhaps a script to automate the setup to come!

Update 11/6/25:
Pics and hopefully usable tutorial

Todo:

  1. Getting parts to house an external setup (pins unfortunately still need to be connected to board in some way).
  2. Pull power from BBB and internalize components (provide a usb C (non-standard) to the side wall of the cover and make a usb c connector for the probe to cleanly connect to machine (5v and 3.3v!) during probing (no external powersupply needed!)

image3
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If interested this was the trigger time for probe (~7.6 us)