[BUG] Z-home does not work on TronXY X5SA board model CXY-V6-191017

[zhanhongliau]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

Z Homing doesn't do anything when I select the Auto Home option. X and Y work well, the printhead moves to the X and Y endstops, but when it returns to the center of the bed to do Z homing, the bed just drops down about 10mm, pauses for a split second, then moves downwards again another 10mm.

I've noticed that the Z home will work if I move the bed close enough to the Z probe that it activates (the light turns on). But this means that after every print where the bed ends up far from the probe (Z axis is way positive), if I turn off the machine I have to manually move the bed up towards the probe, then select autohome, and then hope the bed is properly aligned when I start printing.

It appears the board I have is the new 'silent motherboard' model CXY-V6-191017 with TMC drivers but I neglected to take a pic of it when I had the case opened.

I found an older issue here where a user toggled pullup on pin PA14 but I tried putting his code in the setup function in MarlinCore.cpp and that didn't seem to do anything. Building on chitu_f103 or chitu_v5_gpio_init doesn't seem to change anything either.

Bug Timeline

Started when I updated the firmware from the stock version to a Marlin build

Expected behavior

I expected Z home to work. The original firmware by TronXY I think is based on Marlin as well and I remember the two prints I did with it seemed to properly move the bed upwards to find Z home regardless of the starting position of the bed.

Actual behavior

When it starts to do Z homing, the bed moves down a short distance, pauses, then moves down a short distance again and stops.

Steps to Reproduce

1. Power off the printer
2. Move the bed some distance from the probe/nozzle, maybe about 30mm
3. Turn on the printer, then select Auto Home

Version of Marlin Firmware

FIRMWARE_NAME:Marlin bugfix-2.1.x (Jul 21 2022 09:44:52) 
SOURCE_CODE_URL:github.com/MarlinFirmware/Marlin 
PROTOCOL_VERSION:1.0 
MACHINE_TYPE:Tronxy X5SA V6 330 TMC 
EXTRUDER_COUNT:1 UUID:cede2a2f-41a2-4748-9b12-c55c62f367ff

Printer model

TronXY X5SA (330x330 bed size, non-pro)

Electronics

Stock electronics. Board model CXY-V6-191017

Add-ons

No changes to stock hardware

Bed Leveling

ABL Bilinear mesh

Your Slicer

Cura

Host Software

SD Card (headless)

Don't forget to include

• [X] A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

Marlin.zip

[Bob-the-Kuhn]

Enabling #define ENDSTOPPULLUPS should take care of your endstop pullup concerns.

Does M119 report the Z_MIN_PROBE as triggered when not at the home position? If yes then invert Z_MIN_PROBE_ENDSTOP_INVERTING and Z_MIN_ENDSTOP_INVERTING.

[zhanhongliau]

Z_MIN_PROBE_ENDSTOP_INVERTING and Z_MIN_ENDSTOP_INVERTING are already inverted (set to true), and M119 reports Z_MIN_PROBE as open when the bed is far from the probe so that seems fine. I tried to enable ENDSTOPPULLUPS and that ended up causing the limit switches for X and Y to stop working, causing the printer to try to move the head way outside limits (oops). Enabling specifically ENDSTOPPULLUP_ZMIN_PROBE doesn't do anything either, the bed still moves down a bit, pauses, then moves down even more and stops.

I also tried setting Z_MIN_ENDSTOP_INVERTING to false and that actually caused the bed to move upwards during the Z home instead of down! But unfortunately the probe does not trigger and it causes the nozzle to crash into the bed.

With ENDSTOPPULLUPS disabled, and Z_MIN_PROBE_ENDSTOP_INVERTING set to false, the Z home completely doesn't work, even if the bed starts close to the nozzle the bed just shifts downwards a few times and stops. At least with Z_MIN_PROBE_ENDSTOP_INVERTING set to true it was able to home Z if the bed was manually placed close to the nozzle at the start.

Is there anything else I can do to debug this issue?

[zhanhongliau]

Digging into this more it looks like M119 reports Z_min as TRIGGERED on startup! It seems that the key is to trigger the probe once after startup to have it properly detect its real state, only then will Z homing work. This can be as simple as waving my hand in front of the probe.

I've tried building in the chitu_v5_gpio_init environment which supposedly has a bugfix for the incorrect probe state on startup, but that didn't seem to change anything. In boards_setup.cpp

            /**
             * PA14 is a pull up pin. But, some V5 boards it start with LOW state! And just behave properly when the Z- PROBE is actived at least once.
             * So, if the sensor isnt actived, the PA14 pin will be forever in LOW state, telling Marlin the probe IS ALWAYS ACTIVE, that isnt the case!
             * Chitu original firmware seems to start with every pullup PIN with HIGH to workaround this.
             * So we are doing the same here.
             * This hack only works if applied *before* the GPIO Init, it's the reason I did it here.
             */
            #ifdef CHITU_V5_Z_MIN_BUGFIX
              GPIOA->regs->BSRR = (1U << PA14);
            #endif

Putting the pullup line of code in the setup function in MarlinCore.cpp gives me a compile error saying GPIOA has no such member regs. How would I go about forcing the probe to trigger itself once on startup?

[zhanhongliau]

Wow, okay, I just tried adding

  
  SET_INPUT_PULLDOWN(Z_MIN_PIN);
  SET_INPUT_PULLUP(Z_MIN_PIN);
  

To the setup function and that fixed it. Z min does not show as Triggered on startup anymore, and Z home works properly regardless of the starting bed position.

[Bob-the-Kuhn]

Fantastic!

[Barrnet]

Wow, okay, I just tried adding

  
  SET_INPUT_PULLDOWN(Z_MIN_PIN);
  SET_INPUT_PULLUP(Z_MIN_PIN);
  

To the setup function and that fixed it. Z min does not show as Triggered on startup anymore, and Z home works properly regardless of the starting bed position.

I have this problem but I don't understand where put this lines on the file. Could you provide an example please?

[zhanhongliau]

This was added in src/MarlinCore.cpp in the setup function. Basically that setup function looks like

void setup() {
  // I added these 2 lines here
  SET_INPUT_PULLDOWN(Z_MIN_PIN);
  SET_INPUT_PULLUP(Z_MIN_PIN);
  
  #ifdef BOARD_PREINIT
    BOARD_PREINIT(); // Low-level init (before serial init)
  #endif

  // ...
}

I haven't tested this on the latest marlin branch but it worked on the rhapsodyv fork for my TronXY x5sa

[Barrnet]

Sadly it don't work on Marlin 2.1.1 :(

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This issue has had no activity in the last 60 days. Please add a reply if you want to keep this issue active, otherwise it will be automatically closed within 10 days.

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