✨ Extruder with Dual Stepper Drivers (#21403)

Marlin/src/inc/Conditionals_LCD.h

@@ -558,7 +558,12 @@
   #undef DISABLE_E
 #endif
 
-#if ENABLED(SWITCHING_EXTRUDER)   // One stepper for every two EXTRUDERS
+#if ENABLED(E_DUAL_STEPPER_DRIVERS) // E0/E1 steppers act in tandem as E0
+
+  #define E_STEPPERS      2
+
+#elif ENABLED(SWITCHING_EXTRUDER)   // One stepper for every two EXTRUDERS
+
   #if EXTRUDERS > 4
     #define E_STEPPERS    3
   #elif EXTRUDERS > 2
@@ -569,17 +574,24 @@
   #if DISABLED(SWITCHING_NOZZLE)
     #define HOTENDS       E_STEPPERS
   #endif
-#elif ENABLED(MIXING_EXTRUDER)
+
+#elif ENABLED(MIXING_EXTRUDER)      // Multiple feeds are mixed proportionally
+
   #define E_STEPPERS      MIXING_STEPPERS
   #define E_MANUAL        1
   #if MIXING_STEPPERS == 2
     #define HAS_DUAL_MIXING 1
   #endif
-#elif ENABLED(SWITCHING_TOOLHEAD)
+
+#elif ENABLED(SWITCHING_TOOLHEAD)   // Toolchanger
+
   #define E_STEPPERS      EXTRUDERS
   #define E_MANUAL        EXTRUDERS
-#elif HAS_PRUSA_MMU2
+
+#elif HAS_PRUSA_MMU2                // Průša Multi-Material Unit v2
+
   #define E_STEPPERS 1
+
 #endif
 
 // No inactive extruders with SWITCHING_NOZZLE or Průša MMU1

Marlin/src/inc/SanityCheck.h

@@ -1161,6 +1161,19 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
   #endif
 #endif
 
+/**
+ * Dual E Steppers requirements
+ */
+#if ENABLED(E_DUAL_STEPPER_DRIVERS)
+  #if EXTRUDERS > 1
+    #error "E_DUAL_STEPPER_DRIVERS can only be used with EXTRUDERS set to 1."
+  #elif ENABLED(MIXING_EXTRUDER)
+    #error "E_DUAL_STEPPER_DRIVERS is incompatible with MIXING_EXTRUDER."
+  #elif ENABLED(SWITCHING_EXTRUDER)
+    #error "E_DUAL_STEPPER_DRIVERS is incompatible with SWITCHING_EXTRUDER."
+  #endif
+#endif
+
 /**
  * Linear Advance 1.5 - Check K value range
  */

Marlin/src/module/stepper/indirection.h

@@ -645,6 +645,11 @@ void reset_stepper_drivers();    // Called by settings.load / settings.reset
 
   #endif
 
+#elif ENABLED(E_DUAL_STEPPER_DRIVERS)
+  #define E_STEP_WRITE(E,V) do{ E0_STEP_WRITE(V); E1_STEP_WRITE(V); }while(0)
+  #define   NORM_E_DIR(E)   do{ E0_DIR_WRITE(!INVERT_E0_DIR); E1_DIR_WRITE(!INVERT_E0_DIR ^ ENABLED(INVERT_E1_VS_E0_DIR)); }while(0)
+  #define    REV_E_DIR(E)   do{ E0_DIR_WRITE( INVERT_E0_DIR); E1_DIR_WRITE( INVERT_E0_DIR ^ ENABLED(INVERT_E1_VS_E0_DIR)); }while(0)
+
 #elif E_STEPPERS
   #define E_STEP_WRITE(E,V) E0_STEP_WRITE(V)
   #define   NORM_E_DIR(E)   E0_DIR_WRITE(!INVERT_E0_DIR)
@@ -1013,6 +1018,7 @@ void reset_stepper_drivers();    // Called by settings.load / settings.reset
 //
 
 #if ENABLED(MIXING_EXTRUDER)
+
   /**
    * Mixing steppers keep all their enable (and direction) states synchronized
    */
@@ -1020,6 +1026,12 @@ void reset_stepper_drivers();    // Called by settings.load / settings.reset
   #define _CALL_DIS_E(N) DISABLE_STEPPER_E##N () ;
   #define  ENABLE_AXIS_E0() { RREPEAT(MIXING_STEPPERS, _CALL_ENA_E) }
   #define DISABLE_AXIS_E0() { RREPEAT(MIXING_STEPPERS, _CALL_DIS_E) }
+
+#elif ENABLED(E_DUAL_STEPPER_DRIVERS)
+
+  #define  ENABLE_AXIS_E0() do{  ENABLE_STEPPER_E0();  ENABLE_STEPPER_E1(); }while(0)
+  #define DISABLE_AXIS_E0() do{ DISABLE_STEPPER_E0(); DISABLE_STEPPER_E1(); }while(0)
+
 #endif
 
 #ifndef ENABLE_AXIS_E0

Marlin/src/pins/pins_postprocess.h

@@ -543,9 +543,17 @@
 #define _EPIN(p,q) __EPIN(p,q)
 #define DIAG_REMAPPED(p,q) (PIN_EXISTS(q) && _EPIN(p##_E_INDEX, DIAG) == q##_PIN)
 
-// The X2 axis, if any, should be the next open extruder port
-#define X2_E_INDEX E_STEPPERS
+// The E0/E1 steppers are always used for Dual E
+#if ENABLED(E_DUAL_STEPPER_DRIVERS)
+  #ifndef E1_STEP_PIN
+    #error "No E1 stepper available for E_DUAL_STEPPER_DRIVERS!"
+  #endif
+  #define X2_E_INDEX INCREMENT(E_STEPPERS)
+#else
+  #define X2_E_INDEX E_STEPPERS
+#endif
 
+// The X2 axis, if any, should be the next open extruder port
 #if EITHER(DUAL_X_CARRIAGE, X_DUAL_STEPPER_DRIVERS)
   #ifndef X2_STEP_PIN
     #define X2_STEP_PIN   _EPIN(X2_E_INDEX, STEP)