[BUG] MMU2S/MMU3: LCD freezes when printing

[rerickson1]

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

Yes, and the problem still exists.

Bug Description

1. MMU2S enabled in Marlin
2. When the print starts the LCD freezes and never updates
3. The print works fine and completes
4. The LCD unfreezes

Bug Timeline

Has been present since the v2.1.2.1 release

Expected behavior

Should be able to use the MMU2S without affecting the LCD operation.

Actual behavior

No response

Steps to Reproduce

No response

Version of Marlin Firmware

https://github.com/rerickson1/Marlin/tree/rde/2.1.x_2/a8%2B_custom

Printer model

Modified Anet A8+

Electronics

MKS SGEN L V2

LCD/Controller

Anet A8+ LCD

Other add-ons

No response

Bed Leveling

UBL Bilinear mesh

Your Slicer

Prusa Slicer

Host Software

OctoPrint

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

No response

[rerickson1]

My config:
config.zip

My code: https://github.com/rerickson1/Marlin/tree/rde/2.1.x_2/a8%2B_custom

[rerickson1]

I have tried increasing all buffers and it did not make a difference. Maybe more adjustments are needed?

Recv: D576 P:0 0 (0) B:3 42 (14)
Recv: D576 P:0 0 (0) B:3 36 (10)
Recv: D576 P:0 0 (0) B:3 109 (41)

[robherc]

ummm...you're using a remix & not official marlin ... and you also haven't told what control board you're using.

[rerickson1]

Control board is listed up in the description.
What do you mean by remix? I have taken vanilla marlin and applied the config settings for my board:

Without any customizations to marlin, this issue happens.

[rerickson1]

I have noticed the LCD only freezes when printing is in progress and there is motion in X/Y directions.
During a tool change when there is no X/Y motion, the LCD unfreezes.
Video:
https://youtu.be/nyE4K4mlIH8
What can I try to troubleshoot this issue?

[eoyilmaz]

This is a duplicate of #24813

I looked into this recently and found a couple of possible sources that can cause this, but it is still freezing... Hopefully this will fix it 😉 : #26523

[rerickson1]

@thisiskeithb I would really like to help get to the bottom of this. This issue is present with this PR: #26635

There must be some loop starving the LCD update task. How can I enable some advanced debug? I tried increasing buffers and it didn't solve the issue, but maybe I did it wrong.

[tommylux]

I'm experiencing slow performance with the LCD when printing through OctoPrint. The LCD seems to lag, moving only one notch when I turn the dial, and often appears frozen. Pressing the dial selects a different menu because the selection hasn't updated. If I wait too long, the menu often closes out. I'm wondering if the buffer is getting overloaded and if there's a way to limit the number of commands OctoPrint sends. Any suggestions would be greatly appreciated. Thanks!

Look forward to any suggestion.

Thanks

[rerickson1]

@thisiskeithb I am looking into this again. The LCD screen still freezes when printing and using MMU3. There are no pin conflicts on my board. I have ensured the UART pins I am using for the MMU3 are not used by anything else on my board schematic.
I am printing with Octoprint, not from an SD card.

I am using bug-fix-2.1.x commit 485fbf2
My configs are here:
https://github.com/rerickson1/Marlin/blob/rde/2.1.x_mmu3-6/Marlin/Configuration.h
https://github.com/rerickson1/Marlin/blob/rde/2.1.x_mmu3-6/Marlin/Configuration_adv.h

I have adjusted buffers:

#define SLOWDOWN_DIVISOR 64
#define BLOCK_BUFFER_SIZE 64
#define BUFSIZE 32
#define TX_BUFFER_SIZE 128
#define RX_BUFFER_SIZE 2048
#define RX_BUFFER_MONITOR
#define MARLIN_DEV_MODE
#define BUFFER_MONITORING

I enabled buffer monitoring while printing:
D576 S2

Recv: D576 P:0 0 (0) B:31 13717 (58)
Recv: D576 P:0 0 (0) B:31 50 (11)
Recv: D576 P:1 0 (0) B:32 48 (10)
Recv: D576 P:0 0 (0) B:31 56 (11)

Based on the report, this means all 64 planner buffers are in use correct? Is that a problem? What else can I do to dig into this further?