[BUG] SKR Pro 1.1 BLTouch is frequently deploying during print

[DarkShortie]

Bug Description

I've recently migrated to a SKR Pro 1.1 board and I'm using a BLTouch. The BLTouch deploys frequently deploys during the print. If it hits the build plate it goes into error state, if Z is raised enough to fully deploy it stays deployed and crashes into the printed object sooner or later.

I've already did a lot of test to find the cause:

• separated the BLTouch wires from the rest to ensure no interference from other wires going to the print head
• changed the wires to the BLTouch to ensure they are not broken
• tried different pins (PA1, PA2, PC9) to ensure no interference on the board itself
• turned the skrew on top of the BLTouch one round counter clockwise

Nothing of this helped. The only workaround I found so far is to pull the servo wire from the SKR after G28 is done. 5V, GND and Z min stays connected. So I think for some reasons deploy commands are send frequently during the print.

My Configurations

config.zip

Steps to Reproduce

1. Use a SKR Pro 1.1 with latest Marlin bugfix 2.0
2. Start a print

Expected behavior:
Print is started, G28 is executed and during the print the BLTouch doesn't deploy.

Actual behavior:
Print is started, G28 is executed and during the print the BLTouch is deploying frequently.

[MangaValk]

I have been investigating this for a while.
Seems something is going wrong with the timer used for servo, but couldn't find a solution yet.

Also the turn off servo after move doesn't seem to work. This would be a possible solution if it worked.

[boelle]

turning off servo after move works fine for me, but using a re-arm

[davidcgu]

I have a bltouch clone and have no issue at all, this use to be a lose connection problem o bad cable.

Regards

[thisiskeithb]

@DarkShortie: Do you have a genuine BLTouch or a clone?

[davidcgu]

Note: connect the contact to Zmin switch

[TB1405]

i also have sometimes problems with my skr pro and BL Touch. but iam not 100% could also be a cable problem.

[DarkShortie]

It's a genuine BLTouch, but a very old one, it's Smart V1.0.
I already tried different pins and also a different cable and separated the cable from the others.

I will try turn of servo after move tomorrow, I was not aware about this option so far..

[RudyBenner]

The header for the BLTouch uses PA2 , change 2 lines as indicated. 825 and 843

[DarkShortie]

Also with DEACTIVATE_SERVOS_AFTER_MOVE activated it doesn't work.

[TB1405]

i also checked my cables now. Cable are all okay. i think it is a bug

[davidcgu]

I told you.... don't connect to PA2, connect to Zmin endstop

[randellhodges]

This is a real question, not a snarky response. I am not the OP and I am using the zmin endstop myself on an SKR PRO 1.1 (just started using this board), but I'm curious.

Why would that change the behavior? PA2/zmin endstop should be read when it deployed and undergoing homing. Deploying the pin is triggered on one of the other pins/servo.

Is it maybe that PA2 is noisy or something that is causing the BLTouch to freak out and drop the pin?

[davidcgu]

The only I can tell you is that I have a bltiuch clone running on a skr pro and have no problem at all with the latest release at least since september.

I have updated the firmware frequently and actually running with the latest release.

So I really doubt there is a but that only afects to youm but never knows...

Regards

[DarkShortie]

Like I wrote before I already tried different pins.

[DarkShortie]

I had the chance to try it with a genuine BLTouch Smart V 3.1, the issue stays the same.

Regarding DEACTIVATE_SERVOS_AFTER_MOVE which was mentioned earlier, this is automatically deactivated when using a BLTouch:

Marlin/Marlin/src/inc/Conditionals_LCD.h

Line 468 in 432decd

#undef DEACTIVATE_SERVOS_AFTER_MOVE

But even if I comment this undef and enable DEACTIVATE_SERVOS_AFTER_MOVE then BLTouch stops working completly.