[BUG] Extendable MMUs with not precisely 5 slots fail with compile error from SanityCheck.h

[codingcatgirl]

Did you test the latest bugfix-2.0.x code?

Yes, and the problem still exists.

Bug Description

When setting #define MMU_MODEL EXTENDABLE_EMU_MMU2S in the configuration, which refers to MMUS with configurable number of filaments, and set EXTRUDERS to a number that is not 5, i get the following compile error:

PRUSA_MMU2(S) requires exactly 5 EXTRUDERS. Please update your Configuration

Additionally, if you set the number of extruders to more than 8 (which should be possible, since up to 15 are supported for an extendable MMU accoring to the source code, i additionally get the following compile error:

Marlin supports a maximum of 8 EXTRUDERS.

Both of these messages shouldn't appear. I've checked the bugfix branch and the problems persist there.

Bug Timeline

The bug of extendable MMUs actually not being extendable has, as far as i can see, been present since the feature of extendable MMU2 was introduced.

Expected behavior

I should be able to run an extendable MMU with a different number than 5 slots, and even with more than 8 slots.

Actual behavior

Marlin fails during debug time because the MMU doesn't have precisely 5 slots and because there are more slots than Marlin supposedly supports.

Steps to Reproduce

1. Set #define MMU_MODEL EXTENDABLE_EMU_MMU2S in Configuration.h
2. Set #define EXTRUDERS 10 in Configuration.h
3. Try to compile, and observe SanityCheck.h throwing errors.

Version of Marlin Firmware

2.0.8.2

Printer model

No response

Electronics

No response

Add-ons

No response

Your Slicer

No response

Host Software

No response

Additional information & file uploads

They issue can be quickly traced down here:

In this code, when MMU_MODEL EXTENDABLE_EMU_MMU2S is set, it results in the following values being defined:

#define HAS_PRUSA_MMU2 1    
#define HAS_PRUSA_MMU2S 1  
#define HAS_EXTENDABLE_MMU 1

However, neither here nor here is HAS_EXTENDABLE_MMU actually checked before throwing a compile error.

I'm a bit surprised that i seem to be the first person noticing this and i'm wondering if i'm the first person to actually try to run a MMU with more than 5 slots on Marlin, since this problem seems to have already been there in the commit that introduced this feature (#19912).

It would be nice if this issue could be fixed please :) Paging @GMagician because they wrote this specific feature. (Thank you for your work! I have designed my own extendable MMU and was so happy to see that i wouldn't have to make changes to Marlin because this feature was just recently added… well, almost :P)

[codingcatgirl]

I just commented out these compile errors to see if it will just work then, and the answer is sadly no.

In file included from Marlin/src/inc/MarlinConfigPre.h:37:0,
                 from Marlin/src/inc/MarlinConfig.h:28,
                 from Marlin/src/MarlinCore.h:24,
                 from Marlin/src/MarlinCore.cpp:31:
Marlin/src/MarlinCore.cpp: In function 'void disable_e_stepper(uint8_t)':
Marlin/src/MarlinCore.cpp:318:52: error: 'DISABLE_AXIS_E8' was not declared in this scope
   #define _CASE_DIS_E(N) case N: DISABLE_AXIS_E##N(); break;

Marlin tries to use code/macors for extruders with index > 7 which unsurprisingly don't exist, since Marlin doesn't support more than 8 extruders. This happens despite SINGLENOZZLE being defined (but it gets defined here so that shouldn't make a difference). And yep, i've also uncommented the #undef SINGLENOZZLE from this line – why is that line there, looks like a mistake to me?

It really seems like there might be quite a bit of work still to do in order to make this feature actually work? I can't help but get the impression that the extendability that the code/pull request promised to introduce wasn't tested at all.

[GMagician]

I can't help but get the impression that the extendability that the code/pull request promised to introduce wasn't tested at all.

I stopped to 5 actually because my MMU was extendable but just with standard nr of colors

[thisiskeithb]

Fixed in #22036

[github-actions]

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