BlTouch randomly crashes and its not the cable

Hello :wink:
I know, i’m not the first one, but i can’t get a bltouch to work properly and since i ruled out every other possibility i ask here for help.

So, randomly, like every fouth to every 40th attempt a probing fails and ends in a headcrash.

  • Anet Et4 (i know)
  • original BLTouch V3.1
  • Raspberry Pi3B V1.2
  • Mainsail OS

So, since adding a BLTouch to the Printerboard is a little difficult i added the Raspberry as MCU and drive it from there. Controlpin works fine. As Sensorpin i use GPIO0 or GPIO1 since they have an inbuild pullup.

After initial setup i receive several crashes. So i

  • build a connectorcable from a CAT6 cable → same result
  • switched to the probe-pin from my Anet Board → same result
  • ordered a new BLTouch → same result

So in general it’s working, but expecting a crash before every print makes it unusable. In the Log you will find a working manual check, a working home command and during probe_accuracy the thrid attempt failed.

How could i debug this futher?
Thanks for your help!

klippy(5).log (155.6 KB)

So from the looks of it, the probe is deploying correctly, but it is not triggering when it touches the bed, is that right? The red LED on the probe changes state when the probe is deployed (it goes out) and again when it is triggered (LED comes on), is that what you are seeing? I’m afraid that I don’t have a solution as yet, just trying to better understand what is going on in the hopes that I can help

you are correct! the probe deployes, light goes out, touches bed, red light goes on, but the nozzle crashes anyway.

I have to test this a little further but it looks like if i don’t test manually wie bltouch_debug, the success rate of the probe increases a lot. in 100 probes i had like 2 fails the last day. not perfect, but okay enough. I’m still going to have an eye on this.

Check out this page: BL-Touch - Klipper documentation

Spcifically, see the sections titled “BL Touch Clones” and “BLTouch V3”, I suspect that you may need to play around with these settings. I see that you already have “probe_with_touch_mode” set to true, but I would try also setting “pin_up_touch_mode_reports_triggered: False” as well. The doc referenced above says that this is not needed with a genuine BTouch, but I have it in my config file and it works fine with my BLTouch V3.1. You’ve got nothing to lose by giving it a try.

It really sounds to me like electrical noise is adding interference to the signal wire, causing false readings. The doc makes reference to a noise filtering capacitor between the signal wire and ground, but gives no further info, so that may be worth googling. If all else fails, I would try adding a small cap (say 1uF to 10uF) on the mainboard-side of the cable and see if that makes things more reliable. But google this first and see if you can find more info.