G38 Probe Target implementation

Mostly Printed CNC - MPCNC Advice
1

I’m trying to get G38.2 to work. I started with the firmware from the firmware page and made a couple of changes to the Configuration.h and Configuration_adv.h files and then flashed the firmware. The commands now trigger an action. However, the axis doesn’t stop when the touch plate is hit. It appears to be a known bug in the 1.1.0-1 firmware (I think that is the version from the firmware page). It has been fixed with firmware after 1.1.0-RC8 .

The way I see it I have four options:

1 . Jump to the latest firmware from the Marlin page and try to change the settings in Configuration.h and _adv.h to match those from the V1 firmware page.

  1. Use the latest firmware from the Allted/Marlin github page and make the probe changes to those configuration.h files

  2. Use 1.1.0 RC8 with a new endstops.cpp file (like is mentioned here https://www.v1engineering.com/forum/topic/touch-plate-with-g38-codes/)

  3. Bag it and move on with my project.

Any advice? I’m leaning towards option 2. Has anyone used G38 since P3DCNC’s post March 2017?

Thanks.

2

Start with 2 for sure. See what happens. So much has changed since RC8.

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3

Ok. I went for option 2, Downloaded MPCNC_MRambo_T8_16T_LCD branch from Allted/Marlin github and made a few changes to configuration.h: defined FIX_MOUNTED_PROBE and setting INVERT_X_DIR, INVERT_Y_DIR, INVERT_Z_DIR to all true (that was easier than flipping the connectors) . In Configuration_adv.h, I defined G38_PROBE_TARGET.

Sadly, same effect G38.2 moves the axis (X, Y or Z), but doesn’t stop when the Z endstop is triggered. Nice splash screen on the v2 firmware though.

If I did something obviously wrong or if I missed a setting, let me know. I’ll continue to work it.

4

Try M119 to see your end stop status, then manually trigger the connection and try it again. You might have a wiring issue between the z plate and your board or between the bit and your board.

5

Good advice. G28 Z was working ok, so I figured the wires/connections were good. I’ll look at m119 tonight.

6

Solved, but it wasn’t pretty and Marlin has a bug here I think. From some research it appears this “bug” has been fixed and then comes back often as the other end stop and bed leveling features evolve.

For future reference: I made the changes as above and then had to edit the endstops.cpp file to change the #if ENABLED(G38_PROBE_TARGET) section of the code to read the Z_MIN instead of the Z_MIN_PROBE and comment rest of the conditional. This is because I don’t think Z_MIN_PROBE is actually getting set when Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN in Configuration.h is set.

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7

Hey Mark

i was having the same issue as you and fixed it by editing the endstop.ccp like in your comment.

Thanks for the answer to this problem

8

You should be able to use newer versions of marlin without issue. I found that manually configuring Z_MIN_PROBE_PINfixed my issues. Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN seems buggy and doesn’t set the appropriate pin to be monitored by G38.

Thread documenting what I tried here: https://www.v1engineering.com/forum/topic/g38-x-support-in-marlin/

My fork of marlin: https://github.com/mzizzi/Marlin/tree/MPCNC_Rambo_T8_16T_LCD_mzizzi

Manually setting Z_MIN_PROBE_PIN: https://github.com/mzizzi/Marlin/blob/MPCNC_Rambo_T8_16T_LCD_mzizzi/Marlin/Configuration.h#L799

9

With the latest firmware (Ryan updated a couple weeks ago) it is possible to get this working with just Configuration.h and Configuration_adv.h, no changes to any cpp files are necessary.

There does appear to (still) be some weirdness around Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN, and as far as I know this must be disabled (even if using the zmin connector on the board).

My configuration (including other stuff specific to my machine) has G38 working and is outlined here: https://www.v1engineering.com/forum/topic/running-ryans-latest/

 

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