Yup - another "Lost Communication with MCU" problem

General Discussion
1

Basic Information:

Printer Model: Ender 3 Pro
MCU / Printerboard: 4.2.7 Silent
Host / SBC Pi 5
klippy.log

4.2.7 silent MCU (it started producing this error with the old 4.2.2 so I upgraded last week)

BD Sensor

All sections are up to date via the Mainsail update manager.

I’ve only been running Klipper for a couple of months, it’s been great until the last couple of weeks.

If i do short (less than 90 min) prints I never have an issue. If I load a long print (2hr +) it fails at random times.

I’ve had it stop at 16 mins, 42 mins, 2 hrs … all over the place. The error is always the same.

I’ve tried with and without the webcam (Logitech C920).

Upgrading the MCU and it still happens.

I’ve seen many posts about the “lost communication” issue, and I’ve done all of the suggested fixes:

  • Checked all wiring
  • Replaced USB cable 5 times between MCU and Pi (I guess all of them could have been dodgy…)
  • No overheating issues
  • Checked Pi power supply is 5.2v (listed as 4.5amp but I haven’t measured this)
  • Started from scratch with both Pi and MCU software/flashing (at least 3 times)
  • Tried all 4 of the Pi USB ports
  • Serial Port is correct
  • Taped over the 5v + supply on the USB cable from Pi
  • vcgemcmd get_throttled=0x0

I’ve setup the software both ways - manually, and by using KIAUH. Made no difference.

I’ve attached a klippy log that I have no idea how to read or decipher - I’m hoping there is something in it that will point me in the right direction.

I’m going to try more USB cables, but any guidance here would be gratefully welcomed.

Thanks.
klippy.zip (272.5 KB)

2

Hello @sootvpn !

It appears that the issue does not appear in the log.

You may also check the stability of the USB connector on the printer board.

3

Can you define what you mean by “check stability of the usb connector”

4

I mean the mechanical stability.

  • Does the plug wiggle in the socket.
  • Is the socket tight to the board.
5

Yup. MCU is 1 week old, Pi less than 4 weeks.

And I had the issue with the 4.2.2 board which is why I swapped out - and I also tried with my Pi 4.

I’m just starting to think I’m just having a bad luck run with the cables as they are the only common denominator.

6

UPDATE/SOLVED: The PSU was a fake. I purchased a new genuine Mean Well, wired it in, boom! So the conclusion is that after a bit of time, the fake unit was putting out something odd in regards to voltage or amps, and killing the connection between MCU and Pi.

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