Communication timeout while printing. Ender 2 Pro. Advice required

What is the problem?

Every minute or so, the extruder will pause for a second or 2 leaving a blob of plastic.
This is the log from /var/log/syslog:

Jul 25 15:27:46 octopi octoprint[360]: 2022-07-25 15:27:46,769 - octoprint.util.comm - INFO - Communication timeout while printing, trying to trigger respon
se from printer.#033[0m
Jul 25 15:27:46 octopi octoprint[360]: 2022-07-25 15:27:46,801 - octoprint.util.comm - INFO - Got a resend request from the printer: requested line = 2848,
current line = 2850
Jul 25 15:27:46 octopi octoprint[360]: | Last lines in terminal:
Jul 25 15:27:46 octopi octoprint[360]: | Send: N2845 G1 X74.433 Y89.262 E.04812*102
Jul 25 15:27:46 octopi octoprint[360]: | Recv: ok
Jul 25 15:27:46 octopi octoprint[360]: | Send: N2846 G1 X73.389 Y89.078 E.04812*109
Jul 25 15:27:46 octopi octoprint[360]: | Recv: ok
Jul 25 15:27:46 octopi octoprint[360]: | Send: N2847 G1 X72.368 Y88.791 E.04812*99
Jul 25 15:27:46 octopi octoprint[360]: | Recv: ok
Jul 25 15:27:46 octopi octoprint[360]: | Send: N2848 G1 X71.381 Y88.404 E.04812*103
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:59.99 /60.00 (857.06) @:91 B@:48
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:90 B@:43
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:90 B@:43
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:90 B@:43
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:90 B@:43
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:90 B@:43
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:90 B@:43
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:90 B@:43
Jul 25 15:27:46 octopi octoprint[360]: | Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:90 B@:43
Jul 25 15:27:46 octopi octoprint[360]: | Communication timeout while printing, trying to trigger response from printer. Configure long running commands or i
ncrease communication timeout if that happens regularly on specific commands or long moves.
Jul 25 15:27:46 octopi octoprint[360]: | Send: N2849 M105*16
Jul 25 15:27:46 octopi octoprint[360]: | Recv: Error:checksum mismatch, Last Line: 2847
Jul 25 15:27:46 octopi octoprint[360]: | Recv: Resend: 2848#033[0m

What did you already try to solve it?

I've tried changing cables and re-routing the USB cable. My next step is to buy a smaller cable and ferrite ring.

Have you tried running in safe mode?

Yes

Did running in safe mode solve the problem?

No

Systeminfo Bundle

You can download this in OctoPrint's System Information dialog ... no bundle, no support!)

Printer: Creality Ender 2 Pro

WRITE HERE
octoprint-systeminfo-20220725154303.zip (257.8 KB)

It does look like a generic communication problems with the printer. The printer is complaining about things OctoPrint is sending it not reaching it. The resends and timeouts are definitely going to be causing the blobs on prints.

With Creality printers it is not uncommon to have communication issues, as their hardware can be questionable. I would recommend to go ahead with buying a high quality smaller cable, that's a common fix. You can search the forum for many posts about various fixes people use. Creality's software is not known for being high quality and bug free, so if you are using stock firmware it may be that non-Creality provided firmware would work better.

Trying safe mode might help because I think you have some plugins (DisplayLayerProgress) that would also send stuff to the serial connection. It doesn't look like it is choking on any particular lines, just normal movement commands.

Finally, the Pi is reporting at some points that it has had undervoltage, so you may need a better power supply on the Pi or use less peripherals.

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I tried safe mode after thinking the DisplayLayerProgress might be causing problems and it still has the issue.
I fixed the undervoltage issue by changing the Pi's USB power cable.

For you are using a Creality machine, one of the common tricks may help:

  • Put tape on the 5V pin - Why and how

  • Run with/without SD card in the printer's SD card slot.

  • Relocating the USB cable away from stepper motors and their cables and from the LCD and it's cable. Using ferrite beads on the USB cable.

I've so far tried running without the SD card, moving the USB cable and adding ferrite beads. Nothing seems to work.

Also tried putting tape on the 5V pin. The printer still worked, but it didn't stop the errors.

Creality printers are very susceptible to EMI and they are also generators of EMI. This is often a deadly combination. The USB cable should be short, shielded, and have ferrite beads. The routing of the USB cable can also be crucial as well as the routing of other cables inside the printer. You can search this forum for "communication" and find numerous topics and a collection of things to try to resolve this issue.

All I can say is keep trying things until it starts working.

I'm still trying various things - moving the pi, changing USB cables etc. Very difficult finding a decent micro USB cable on Amazon.

Looking at the serial log, it is always lines like this that cause the issue:

2022-07-27 12:36:02,282 - Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:92 B@:38
2022-07-27 12:36:04,281 - Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:92 B@:38
2022-07-27 12:36:06,281 - Recv:  T:200.00 /200.00 (109.00) B:60.00 /60.00 (857.00) @:92 B@:38
2022-07-27 12:36:06,283 - Communication timeout while printing, trying to trigger response from printer. Configure long running commands or increase communication timeout if that happens regularly on specific commands or long moves.

Here's one on Amazon, https://www.amazon.com/Monoprice-3-Feet-Micro-24AWG-Ferrite/dp/B004C4WEVI?th=1. Other lengths are available.

You might also look at this topic, https://community.octoprint.org/t/usb-cable-quality-necessary/32589/14. Note the part about shielding the cable that goes from the printer mainboard to the display of the printer.

Unfortunately that cable isn't available in the UK unless you order the 4.5m one!
I could try screening the display cable.

I resolved communication timeouts that are caused by EMI messing with the printer by installing an EMI filter on the mains cable to the printer. Was originally going to fit the filter in the printer but space a bit tight. You can also use a multibox that has the filter built in. Solved all my problems :wink:

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Do you have power loss recovery enabled on the printer?

That is also known to cause pauses which result in small blobs.

I turned that off as I heard it caused issues.