Automatically set X2 stepper pins

.travis.yml

   # Test DUAL_X_CARRIAGE
   #
   - restore_configs
-  - opt_set MOTHERBOARD BOARD_RAMPS_14_EEB
+  - opt_set MOTHERBOARD BOARD_RUMBA
   - opt_set EXTRUDERS 2
   - opt_set TEMP_SENSOR_1 1
   - opt_enable USE_XMAX_PLUG

Marlin/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/Felix/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/Hephestos/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/Hephestos_2/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/K8200/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/RigidBot/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/SCARA/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/TAZ4/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/WITBOX/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/delta/biv2.5/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/delta/generic/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/delta/kossel_mini/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/delta/kossel_pro/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/delta/kossel_xl/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/makibox/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/example_configurations/tvrrug/Round2/Configuration_adv.h

 // Enable this for dual x-carriage printers.
 // A dual x-carriage design has the advantage that the inactive extruder can be parked which
 // prevents hot-end ooze contaminating the print. It also reduces the weight of each x-carriage
-// allowing faster printing speeds.
+// allowing faster printing speeds. Connect your X2 stepper to the first unused E plug.
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
   // Configuration for second X-carriage
       // without modifying the firmware (through the "M218 T1 X???" command).
       // Remember: you should set the second extruder x-offset to 0 in your slicer.
 
-  // Pins for second x-carriage stepper driver (defined here to avoid further complicating pins.h)
-  #define X2_ENABLE_PIN 29
-  #define X2_STEP_PIN 25
-  #define X2_DIR_PIN 23
-
   // There are a few selectable movement modes for dual x-carriages using M605 S<mode>
   //    Mode 0: Full control. The slicer has full control over both x-carriages and can achieve optimal travel results
   //                           as long as it supports dual x-carriages. (M605 S0)

Marlin/macros.h

 #define NUMERIC_SIGNED(a) (NUMERIC(a) || (a) == '-')
 #define COUNT(a) (sizeof(a)/sizeof(*a))
 
+// Macros for adding
+#define INC_0 1
+#define INC_1 2
+#define INC_2 3
+#define INC_3 4
+#define INC_4 5
+#define INC_5 6
+#define INC_6 7
+#define INC_7 8
+#define INC_8 9
+#define INCREMENT_(n) INC_ ##n
+#define INCREMENT(n) INCREMENT_(n)
+
+// Macros for subtracting
+#define DEC_1 0
+#define DEC_2 1
+#define DEC_3 2
+#define DEC_4 3
+#define DEC_5 4
+#define DEC_6 5
+#define DEC_7 6
+#define DEC_8 7
+#define DEC_9 8
+#define DECREMENT_(n) DEC_ ##n
+#define DECREMENT(n) DECREMENT_(n)
+
 #define PIN_EXISTS(PN) (defined(PN ##_PIN) && PN ##_PIN >= 0)
 
 #define PENDING(NOW,SOON) ((long)(NOW-(SOON))<0)

Marlin/pins.h

       #define _E3_PINS E3_STEP_PIN, E3_DIR_PIN, E3_ENABLE_PIN, HEATER_3_PIN, EXTRUDER_3_AUTO_FAN_PIN, marlinAnalogInputToDigitalPin(TEMP_3_PIN),
     #endif
   #endif
-#elif ENABLED(Y_DUAL_STEPPER_DRIVERS) || ENABLED(Z_DUAL_STEPPER_DRIVERS)
-  #undef _E1_PINS
-  #define _E1_PINS E1_STEP_PIN, E1_DIR_PIN, E1_ENABLE_PIN,
 #endif
 
 #define BED_PINS HEATER_BED_PIN, marlinAnalogInputToDigitalPin(TEMP_BED_PIN),
 #endif
 
 //
-// Dual Y and Dual Z support
-// These options are mutually-exclusive
+// Dual X-carriage, Dual Y, Dual Z support
 //
 
+#define _X2_PINS
+#define _Y2_PINS
+#define _Z2_PINS
+
 #define __EPIN(p,q) E##p##_##q##_PIN
 #define _EPIN(p,q) __EPIN(p,q)
 
+#if ENABLED(DUAL_X_CARRIAGE)
+  // The X2 axis, if any, should be the next open extruder port
+  #ifndef X2_STEP_PIN
+    #define X2_STEP_PIN   _EPIN(EXTRUDERS, STEP)
+    #define X2_DIR_PIN    _EPIN(EXTRUDERS, DIR)
+    #define X2_ENABLE_PIN _EPIN(EXTRUDERS, ENABLE)
+  #endif
+  #undef _X2_PINS
+  #define _X2_PINS X2_STEP_PIN, X2_DIR_PIN, X2_ENABLE_PIN,
+  #define Y2_Z2_E_INDEX INCREMENT(EXTRUDERS)
+#else
+  #define Y2_Z2_E_INDEX EXTRUDERS
+#endif
+
 // The Y2 axis, if any, should be the next open extruder port
-#ifndef Y2_STEP_PIN
-  #define Y2_STEP_PIN   _EPIN(EXTRUDERS, STEP)
-  #define Y2_DIR_PIN    _EPIN(EXTRUDERS, DIR)
-  #define Y2_ENABLE_PIN _EPIN(EXTRUDERS, ENABLE)
+#if ENABLED(Y_DUAL_STEPPER_DRIVERS) && !defined(Y2_STEP_PIN)
+  #define Y2_STEP_PIN   _EPIN(Y2_Z2_E_INDEX, STEP)
+  #define Y2_DIR_PIN    _EPIN(Y2_Z2_E_INDEX, DIR)
+  #define Y2_ENABLE_PIN _EPIN(Y2_Z2_E_INDEX, ENABLE)
+  #undef _Y2_PINS
+  #define _Y2_PINS Y2_STEP_PIN, Y2_DIR_PIN, Y2_ENABLE_PIN,
 #endif
 
 // The Z2 axis, if any, should be the next open extruder port
-#ifndef Z2_STEP_PIN
-  #define Z2_STEP_PIN   _EPIN(EXTRUDERS, STEP)
-  #define Z2_DIR_PIN    _EPIN(EXTRUDERS, DIR)
-  #define Z2_ENABLE_PIN _EPIN(EXTRUDERS, ENABLE)
+#if ENABLED(Z_DUAL_STEPPER_DRIVERS) && !defined(Z2_STEP_PIN)
+  #define Z2_STEP_PIN   _EPIN(Y2_Z2_E_INDEX, STEP)
+  #define Z2_DIR_PIN    _EPIN(Y2_Z2_E_INDEX, DIR)
+  #define Z2_ENABLE_PIN _EPIN(Y2_Z2_E_INDEX, ENABLE)
+  #undef _Z2_PINS
+  #define _Z2_PINS Z2_STEP_PIN, Z2_DIR_PIN, Z2_ENABLE_PIN,
 #endif
 
 #define SENSITIVE_PINS { 0, 1, \
     Z_STEP_PIN, Z_DIR_PIN, Z_ENABLE_PIN, Z_MIN_PIN, Z_MAX_PIN, Z_MIN_PROBE_PIN, \
     PS_ON_PIN, HEATER_BED_PIN, FAN_PIN, FAN1_PIN, FAN2_PIN, CONTROLLERFAN_PIN, \
     _E0_PINS _E1_PINS _E2_PINS _E3_PINS BED_PINS \
+    _X2_PINS _Y2_PINS _Z2_PINS \
     X_MS1_PIN, X_MS2_PIN, Y_MS1_PIN, Y_MS2_PIN, Z_MS1_PIN, Z_MS2_PIN \
   }
 

Marlin/stepper.cpp

   #if HAS_X_ENABLE
     X_ENABLE_INIT;
     if (!X_ENABLE_ON) X_ENABLE_WRITE(HIGH);
+    #if ENABLED(DUAL_X_CARRIAGE) && HAS_X2_ENABLE
+      X2_ENABLE_INIT;
+      if (!X_ENABLE_ON) X2_ENABLE_WRITE(HIGH);
+    #endif
   #endif
-  #if HAS_X2_ENABLE
-    X2_ENABLE_INIT;
-    if (!X_ENABLE_ON) X2_ENABLE_WRITE(HIGH);
-  #endif
+
   #if HAS_Y_ENABLE
     Y_ENABLE_INIT;
     if (!Y_ENABLE_ON) Y_ENABLE_WRITE(HIGH);
-
-  #if ENABLED(Y_DUAL_STEPPER_DRIVERS) && HAS_Y2_ENABLE
-    Y2_ENABLE_INIT;
-    if (!Y_ENABLE_ON) Y2_ENABLE_WRITE(HIGH);
-  #endif
+    #if ENABLED(Y_DUAL_STEPPER_DRIVERS) && HAS_Y2_ENABLE
+      Y2_ENABLE_INIT;
+      if (!Y_ENABLE_ON) Y2_ENABLE_WRITE(HIGH);
+    #endif
   #endif
+
   #if HAS_Z_ENABLE
     Z_ENABLE_INIT;
     if (!Z_ENABLE_ON) Z_ENABLE_WRITE(HIGH);
-
     #if ENABLED(Z_DUAL_STEPPER_DRIVERS) && HAS_Z2_ENABLE
       Z2_ENABLE_INIT;
       if (!Z_ENABLE_ON) Z2_ENABLE_WRITE(HIGH);
     #endif
   #endif
+
   #if HAS_E0_ENABLE
     E0_ENABLE_INIT;
     if (!E_ENABLE_ON) E0_ENABLE_WRITE(HIGH);
   // Initialize Step Pins
   #if HAS_X_STEP
     AXIS_INIT(x, X, X);
+    #if ENABLED(DUAL_X_CARRIAGE) && HAS_X2_STEP
+      AXIS_INIT(x, X2, X);
+    #endif
   #endif
-  #if HAS_X2_STEP
-    AXIS_INIT(x, X2, X);
-  #endif
+
   #if HAS_Y_STEP
     #if ENABLED(Y_DUAL_STEPPER_DRIVERS) && HAS_Y2_STEP
       Y2_STEP_INIT;
     #endif
     AXIS_INIT(y, Y, Y);
   #endif
+
   #if HAS_Z_STEP
     #if ENABLED(Z_DUAL_STEPPER_DRIVERS) && HAS_Z2_STEP
       Z2_STEP_INIT;
     #endif
     AXIS_INIT(z, Z, Z);
   #endif
+
   #if HAS_E0_STEP
     E_AXIS_INIT(0);
   #endif

Marlin/stepper_indirection.h

 #define X_ENABLE_READ READ(X_ENABLE_PIN)
 
 // X2 motor
-#define X2_STEP_INIT SET_OUTPUT(X2_STEP_PIN)
-#define X2_STEP_WRITE(STATE) WRITE(X2_STEP_PIN,STATE)
-#define X2_STEP_READ READ(X2_STEP_PIN)
+#if ENABLED(DUAL_X_CARRIAGE)
+  #define X2_STEP_INIT SET_OUTPUT(X2_STEP_PIN)
+  #define X2_STEP_WRITE(STATE) WRITE(X2_STEP_PIN,STATE)
+  #define X2_STEP_READ READ(X2_STEP_PIN)
 
-#define X2_DIR_INIT SET_OUTPUT(X2_DIR_PIN)
-#define X2_DIR_WRITE(STATE) WRITE(X2_DIR_PIN,STATE)
-#define X2_DIR_READ READ(X_DIR_PIN)
+  #define X2_DIR_INIT SET_OUTPUT(X2_DIR_PIN)
+  #define X2_DIR_WRITE(STATE) WRITE(X2_DIR_PIN,STATE)
+  #define X2_DIR_READ READ(X_DIR_PIN)
 
-#define X2_ENABLE_INIT SET_OUTPUT(X2_ENABLE_PIN)
-#define X2_ENABLE_WRITE(STATE) WRITE(X2_ENABLE_PIN,STATE)
-#define X2_ENABLE_READ READ(X_ENABLE_PIN)
+  #define X2_ENABLE_INIT SET_OUTPUT(X2_ENABLE_PIN)
+  #define X2_ENABLE_WRITE(STATE) WRITE(X2_ENABLE_PIN,STATE)
+  #define X2_ENABLE_READ READ(X_ENABLE_PIN)
+#endif // DUAL_X_CARRIAGE
 
 // Y motor
 #define Y_STEP_INIT SET_OUTPUT(Y_STEP_PIN)
 #define Y_ENABLE_READ READ(Y_ENABLE_PIN)
 
 // Y2 motor
-#define Y2_STEP_INIT SET_OUTPUT(Y2_STEP_PIN)
-#define Y2_STEP_WRITE(STATE) WRITE(Y2_STEP_PIN,STATE)
-#define Y2_STEP_READ READ(Y2_STEP_PIN)
+#if ENABLED(Y_DUAL_STEPPER_DRIVERS)
+  #define Y2_STEP_INIT SET_OUTPUT(Y2_STEP_PIN)
+  #define Y2_STEP_WRITE(STATE) WRITE(Y2_STEP_PIN,STATE)
+  #define Y2_STEP_READ READ(Y2_STEP_PIN)
 
-#define Y2_DIR_INIT SET_OUTPUT(Y2_DIR_PIN)
-#define Y2_DIR_WRITE(STATE) WRITE(Y2_DIR_PIN,STATE)
-#define Y2_DIR_READ READ(Y2_DIR_PIN)
+  #define Y2_DIR_INIT SET_OUTPUT(Y2_DIR_PIN)
+  #define Y2_DIR_WRITE(STATE) WRITE(Y2_DIR_PIN,STATE)
+  #define Y2_DIR_READ READ(Y2_DIR_PIN)
 
-#define Y2_ENABLE_INIT SET_OUTPUT(Y2_ENABLE_PIN)
-#define Y2_ENABLE_WRITE(STATE) WRITE(Y2_ENABLE_PIN,STATE)
-#define Y2_ENABLE_READ READ(Y2_ENABLE_PIN)
+  #define Y2_ENABLE_INIT SET_OUTPUT(Y2_ENABLE_PIN)
+  #define Y2_ENABLE_WRITE(STATE) WRITE(Y2_ENABLE_PIN,STATE)
+  #define Y2_ENABLE_READ READ(Y2_ENABLE_PIN)
+#endif // Y_DUAL_STEPPER_DRIVERS
 
 // Z motor
 #define Z_STEP_INIT SET_OUTPUT(Z_STEP_PIN)
 #define Z_ENABLE_READ READ(Z_ENABLE_PIN)
 
 // Z2 motor
-#define Z2_STEP_INIT SET_OUTPUT(Z2_STEP_PIN)
-#define Z2_STEP_WRITE(STATE) WRITE(Z2_STEP_PIN,STATE)
-#define Z2_STEP_READ READ(Z2_STEP_PIN)
-
-#define Z2_DIR_INIT SET_OUTPUT(Z2_DIR_PIN)
-#define Z2_DIR_WRITE(STATE) WRITE(Z2_DIR_PIN,STATE)
-#define Z2_DIR_READ READ(Z2_DIR_PIN)
-
-#define Z2_ENABLE_INIT SET_OUTPUT(Z2_ENABLE_PIN)
-#define Z2_ENABLE_WRITE(STATE) WRITE(Z2_ENABLE_PIN,STATE)
-#define Z2_ENABLE_READ READ(Z2_ENABLE_PIN)
+#if ENABLED(Z_DUAL_STEPPER_DRIVERS)
+  #define Z2_STEP_INIT SET_OUTPUT(Z2_STEP_PIN)
+  #define Z2_STEP_WRITE(STATE) WRITE(Z2_STEP_PIN,STATE)
+  #define Z2_STEP_READ READ(Z2_STEP_PIN)
+
+  #define Z2_DIR_INIT SET_OUTPUT(Z2_DIR_PIN)
+  #define Z2_DIR_WRITE(STATE) WRITE(Z2_DIR_PIN,STATE)
+  #define Z2_DIR_READ READ(Z2_DIR_PIN)
+
+  #define Z2_ENABLE_INIT SET_OUTPUT(Z2_ENABLE_PIN)
+  #define Z2_ENABLE_WRITE(STATE) WRITE(Z2_ENABLE_PIN,STATE)
+  #define Z2_ENABLE_READ READ(Z2_ENABLE_PIN)
+#endif // Z_DUAL_STEPPER_DRIVERS
 
 // E0 motor
 #define E0_STEP_INIT SET_OUTPUT(E0_STEP_PIN)