avoid some MK2_MULTIPLEXER pitfalls

[revilor]

The MK2_MULTIPLEXER feature requires a set of other configuration options to have the correct values. Some are checked by SanityCheck.h but others are not. To avoid some pitfalls for other users I added a block in Configuration_adv.h to set some requirements for MK2_MULTIPLEXER.

I also had to disable the E1_*_PIN defines in pins_RAMPS.h to get the 2nd extruder working. The corresponding undefs in Configuration_adv.h seem to have no effect on this behalf.

[thinkyhead]

This appears to be a hack to work around a bug. Let's fix the bug!

[thinkyhead]

This is a workaround for a bug elsewhere. When MK2_MULTIPLEXER is set, all E movement should be tailored for that system. This is handled by the stepper_indirection.h code, so let's see if it matches up…

/**
 * Extruder indirection for the single E axis
 */
#if ENABLED(SWITCHING_EXTRUDER)
  . . .
#elif EXTRUDERS > 4
  . . .
#elif EXTRUDERS > 3
  . . .
#elif EXTRUDERS > 2
  . . .
#elif EXTRUDERS > 1
  #if ENABLED(DUAL_X_CARRIAGE) || ENABLED(DUAL_NOZZLE_DUPLICATION_MODE)
    . . .
  #else
    . . .
  #endif
#elif ENABLED(MIXING_EXTRUDER)
  . . .
#else
  #define E_STEP_WRITE(v) E0_STEP_WRITE(v)
  #if ENABLED(MK2_MULTIPLEXER)
    // Even-numbered steppers are reversed
    #define NORM_E_DIR() E0_DIR_WRITE(TEST(current_block->active_extruder, 0) ? !INVERT_E0_DIR: INVERT_E0_DIR)
    #define REV_E_DIR() E0_DIR_WRITE(TEST(current_block->active_extruder, 0) ? INVERT_E0_DIR: !INVERT_E0_DIR)
  #else
    #define NORM_E_DIR() E0_DIR_WRITE(!INVERT_E0_DIR)
    #define REV_E_DIR() E0_DIR_WRITE(INVERT_E0_DIR)
  #endif
#endif

The bug seems to be that if the value for EXTRUDERS isn't "1" the MK2_MULTIPLEXER code will never be applied. So that should be fixed! The correct code should be…

/**
 * Extruder indirection for the single E axis
 */
#if ENABLED(SWITCHING_EXTRUDER)
  . . .
#elif ENABLED(MK2_MULTIPLEXER)   // Even-numbered steppers are reversed
  #define E_STEP_WRITE(v) E0_STEP_WRITE(v)
  #define NORM_E_DIR() E0_DIR_WRITE(TEST(current_block->active_extruder, 0) ? !INVERT_E0_DIR: INVERT_E0_DIR)
  #define REV_E_DIR() E0_DIR_WRITE(TEST(current_block->active_extruder, 0) ? INVERT_E0_DIR: !INVERT_E0_DIR)
#elif EXTRUDERS > 4
  . . .
#elif EXTRUDERS > 3
  . . .
#elif EXTRUDERS > 2
  . . .
#elif EXTRUDERS > 1
  #if ENABLED(DUAL_X_CARRIAGE) || ENABLED(DUAL_NOZZLE_DUPLICATION_MODE)
    . . .
  #else
    . . .
  #endif
#elif ENABLED(MIXING_EXTRUDER)
  . . .
#else
  #define E_STEP_WRITE(v) E0_STEP_WRITE(v)
  #define NORM_E_DIR() E0_DIR_WRITE(!INVERT_E0_DIR)
  #define REV_E_DIR() E0_DIR_WRITE(INVERT_E0_DIR)
#endif

[thinkyhead]

No need for this with above fix.

[thinkyhead]

I've merged the patch described in my review into bugfix-1.1.x. Please confirm that it fixes the issue!

Additional work is still needed to fully integrate the MK2 filament-swapping behavior. It's pretty much a cut-and-paste job from the MK2 branch, except that in adapting it for the main Marlin fork we'll want to make the behaviors —feedrate, retract length, etc.— customizable. We'll aim to get that done for the 1.1.8 release.

[revilor]

I tested the latest bugfix-2.0.x and my extruders 1 and 3 are running backwards now (I don't use the original Prusa extruder set), so your fix works. I still had to set E2_x_PIN and E3_x_PIN because SanityCheck.h requires so. See #8551 and #8552 targeting this issue.

[thinkyhead]

And now those are merged - w00t!