[BUG] Enabling both MPCTEMP and ADAPTIVE_FAN_SLOWING breaks build

[LMBernardo]

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

Yes, and the problem still exists.

Bug Description

Building fails when enabling both MPCTEMP and ADAPTIVE_FAN_SLOWING. This combination is not mentioned anywhere in the MPCTEMP documentation, nor is it mentioned anywhere in the config files, and it seems like these features should be compatible.

I believe that this has gone unnoticed for so long because MPCTEMP is still noted as experimental and unreliable, and I don't think ADAPTIVE_FAN_SLOWING is a particularly common option to enable either. Most likely related to #24687.

Possible Solution

Starting at line 1168 in src/module/temperature.h, there is:

    #if ENABLED(MPCTEMP)
      void MPC_autotune();
    #endif

Marlin builds successfully when this is replaced with the following:

    #if ENABLED(MPCTEMP)
      void MPC_autotune();
      #if ENABLED(ADAPTIVE_FAN_SLOWING)
        static constexpr bool adaptive_fan_slowing = true;
      #endif
    #endif

If these features truly are incompatible, then this will cause other problems. But I don't see why they would be.

Bug Timeline

Old - this has probably existed ever since both features have been available.

Expected behavior

Marlin should either build successfully, or fail with a message stating that these two options cannot be used together. If the latter, this should also be documented somewhere.

Actual behavior

Build fails with the error:

Marlin\src\module\temperature.cpp: In member function 'void Temperature::tr_state_machine_t::run(const_celsius_float_t, const_celsius_float_t, heater_id_t, uint16_t, celsius_t)':
Marlin\src\module\temperature.cpp:2872:15: error: 'adaptive_fan_slowing' was not declared in this scope
           if (adaptive_fan_slowing && heater_id >= 0) {
               ^~~~~~~~~~~~~~~~~~~~
*** [.pio\build\mega2560\src\src\module\temperature.cpp.o] Error 1

Steps to Reproduce

1. Checkout most the recent Marlin bugfix-2.1.x code @ fb5a595

2. Disable PIDTEMP and enable MPCTEMP in Configuration.h

3. Enable ADAPTIVE_FAN_SLOWING in Configuration_adv.h

4. Try to build

Version of Marlin Firmware

bugfix-2.1.x

Printer model

N/A

Electronics

N/A

Add-ons

N/A

Bed Leveling

None

Your Slicer

None

Host Software

None

Don't forget to include

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

Additional information & file uploads

Config.zip

[GMagician]

AFAIK MPC should take care of fan and then adaptive fan shouldn't be necessary.
But let's wait for someone who has knowledge about it

[thisiskeithb]

AFAIK MPC should take care of fan and then adaptive fan shouldn't be necessary.

With MPC_INCLUDE_FAN enabled, ADAPTIVE_FAN_SLOWING shouldn't be necessary, but it's not specifically sanity checked.

[tombrazier]

I have always had ADAPTIVE_FAN_SLOWING enabled along with MPC and no compile error.

[thisiskeithb]

I have always had ADAPTIVE_FAN_SLOWING enabled along with MPC and no compile error.

I would guess something broke it recently.

Using a fresh bugfix-2.1.x pull & disabling PIDTEMP, enabling MPCTEMP & ADAPTIVE_FAN_SLOWING produces the error:

Indexing .pio/build/mega2560/libFrameworkArduino.a
Marlin/src/module/temperature.cpp: In member function 'void Temperature::tr_state_machine_t::run(const_celsius_float_t, const_celsius_float_t, heater_id_t, uint16_t, celsius_t)':
Marlin/src/module/temperature.cpp:2893:15: error: 'adaptive_fan_slowing' was not declared in this scope
           if (adaptive_fan_slowing && heater_id >= 0) {
               ^~~~~~~~~~~~~~~~~~~~
*** [.pio/build/mega2560/src/src/module/temperature.cpp.o] Error 1

[tombrazier]

I do not get the compile error because I have PIDTEMPBED defined. The problem is not with enabling MPCTEMP, it is with disabling PIDTEMP. The same happens if you disable PIDTEMP for bang bang control.

The following code incorrectly couples ADAPTIVE_FAN_SLOWING with PID.

Marlin/Marlin/src/module/temperature.h

Lines 1176 to 1180 in 67bc855

	#if ENABLED(NO_FAN_SLOWING_IN_PID_TUNING)
	static bool adaptive_fan_slowing;
	#elif ENABLED(ADAPTIVE_FAN_SLOWING)
	static constexpr bool adaptive_fan_slowing = true;
	#endif

[tombrazier]

I think https://github.com/tombrazier/Marlin/tree/25115 should fix it. Haven't tried it though.

[thisiskeithb]

Closing since there's now a PR fix this:

• Small PID / MPC related fixes #25314

[github-actions]

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