Quad Z stepper support (#16277)

Marlin/Configuration.h

@@ -670,6 +670,7 @@
 //#define Y2_DRIVER_TYPE A4988
 //#define Z2_DRIVER_TYPE A4988
 //#define Z3_DRIVER_TYPE A4988
+//#define Z4_DRIVER_TYPE A4988
 //#define E0_DRIVER_TYPE A4988
 //#define E1_DRIVER_TYPE A4988
 //#define E2_DRIVER_TYPE A4988

Marlin/Configuration_adv.h

@@ -479,7 +479,7 @@
   //#define X_DUAL_ENDSTOPS
   #if ENABLED(X_DUAL_ENDSTOPS)
     #define X2_USE_ENDSTOP _XMAX_
-    #define X_DUAL_ENDSTOPS_ADJUSTMENT  0
+    #define X2_ENDSTOP_ADJUSTMENT  0
   #endif
 #endif
 
@@ -489,27 +489,28 @@
   //#define Y_DUAL_ENDSTOPS
   #if ENABLED(Y_DUAL_ENDSTOPS)
     #define Y2_USE_ENDSTOP _YMAX_
-    #define Y_DUAL_ENDSTOPS_ADJUSTMENT  0
+    #define Y2_ENDSTOP_ADJUSTMENT  0
   #endif
 #endif
 
-//#define Z_DUAL_STEPPER_DRIVERS
+//
-#if ENABLED(Z_DUAL_STEPPER_DRIVERS)
+// For Z set the number of stepper drivers
-  //#define Z_DUAL_ENDSTOPS
+//
-  #if ENABLED(Z_DUAL_ENDSTOPS)
+#define NUM_Z_STEPPER_DRIVERS 1   // (1-4) Z options change based on how many
-    #define Z2_USE_ENDSTOP _XMAX_
-    #define Z_DUAL_ENDSTOPS_ADJUSTMENT  0
-  #endif
-#endif
 
-//#define Z_TRIPLE_STEPPER_DRIVERS
+#if NUM_Z_STEPPER_DRIVERS > 1
-#if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+  //#define Z_MULTI_ENDSTOPS
-  //#define Z_TRIPLE_ENDSTOPS
+  #if ENABLED(Z_MULTI_ENDSTOPS)
-  #if ENABLED(Z_TRIPLE_ENDSTOPS)
     #define Z2_USE_ENDSTOP          _XMAX_
+    #define Z2_ENDSTOP_ADJUSTMENT   0
+    #if NUM_Z_STEPPER_DRIVERS >= 3
       #define Z3_USE_ENDSTOP        _YMAX_
-    #define Z_TRIPLE_ENDSTOPS_ADJUSTMENT2  0
+      #define Z3_ENDSTOP_ADJUSTMENT 0
-    #define Z_TRIPLE_ENDSTOPS_ADJUSTMENT3  0
+    #endif
+    #if NUM_Z_STEPPER_DRIVERS >= 4
+      #define Z4_USE_ENDSTOP        _ZMAX_
+      #define Z4_ENDSTOP_ADJUSTMENT 0
+    #endif
   #endif
 #endif
 
@@ -1898,6 +1899,12 @@
     #define Z3_MICROSTEPS       16
   #endif
 
+  #if AXIS_DRIVER_TYPE_Z4(TMC26X)
+    #define Z4_MAX_CURRENT    1000
+    #define Z4_SENSE_RESISTOR   91
+    #define Z4_MICROSTEPS       16
+  #endif
+
   #if AXIS_DRIVER_TYPE_E0(TMC26X)
     #define E0_MAX_CURRENT    1000
     #define E0_SENSE_RESISTOR   91
@@ -2015,6 +2022,14 @@
     #define Z3_CHAIN_POS     -1
   #endif
 
+  #if AXIS_IS_TMC(Z4)
+    #define Z4_CURRENT      800
+    #define Z4_CURRENT_HOME Z4_CURRENT
+    #define Z4_MICROSTEPS    16
+    #define Z4_RSENSE         0.11
+    #define Z4_CHAIN_POS     -1
+  #endif
+
   #if AXIS_IS_TMC(E0)
     #define E0_CURRENT      800
     #define E0_MICROSTEPS    16
@@ -2104,6 +2119,7 @@
   #define Y2_SLAVE_ADDRESS 0
   #define Z2_SLAVE_ADDRESS 0
   #define Z3_SLAVE_ADDRESS 0
+  #define Z4_SLAVE_ADDRESS 0
   #define E0_SLAVE_ADDRESS 0
   #define E1_SLAVE_ADDRESS 0
   #define E2_SLAVE_ADDRESS 0
@@ -2179,6 +2195,7 @@
   #define Z_HYBRID_THRESHOLD       3
   #define Z2_HYBRID_THRESHOLD      3
   #define Z3_HYBRID_THRESHOLD      3
+  #define Z4_HYBRID_THRESHOLD      3
   #define E0_HYBRID_THRESHOLD     30
   #define E1_HYBRID_THRESHOLD     30
   #define E2_HYBRID_THRESHOLD     30
@@ -2344,6 +2361,15 @@
     #define Z3_SLEW_RATE         1
   #endif
 
+  #if AXIS_IS_L64XX(Z4)
+    #define Z4_MICROSTEPS      128
+    #define Z4_OVERCURRENT    2000
+    #define Z4_STALLCURRENT   1500
+    #define Z4_MAX_VOLTAGE     127
+    #define Z4_CHAIN_POS        -1
+    #define Z4_SLEW_RATE         1
+  #endif
+
   #if AXIS_IS_L64XX(E0)
     #define E0_MICROSTEPS      128
     #define E0_OVERCURRENT    2000
@@ -2407,7 +2433,7 @@
    *         I not present or I0 or I1 - X, Y, Z or E0
    *         I2 - X2, Y2, Z2 or E1
    *         I3 - Z3 or E3
-   *         I4 - E4
+   *         I4 - Z4 or E4
    *         I5 - E5
    * M916 - Increase drive level until get thermal warning
    * M917 - Find minimum current thresholds

Marlin/src/HAL/HAL_AVR/endstop_interrupts.h

@@ -232,6 +232,22 @@ void setup_endstop_interrupts() {
       pciSetup(Z3_MIN_PIN);
     #endif
   #endif
+  #if HAS_Z4_MAX
+    #if (digitalPinToInterrupt(Z4_MAX_PIN) != NOT_AN_INTERRUPT)
+      _ATTACH(Z4_MAX_PIN);
+    #else
+      static_assert(digitalPinHasPCICR(Z4_MAX_PIN), "Z4_MAX_PIN is not interrupt-capable");
+      pciSetup(Z4_MAX_PIN);
+    #endif
+  #endif
+  #if HAS_Z4_MIN
+    #if (digitalPinToInterrupt(Z4_MIN_PIN) != NOT_AN_INTERRUPT)
+      _ATTACH(Z4_MIN_PIN);
+    #else
+      static_assert(digitalPinHasPCICR(Z4_MIN_PIN), "Z4_MIN_PIN is not interrupt-capable");
+      pciSetup(Z4_MIN_PIN);
+    #endif
+  #endif
   #if HAS_Z_MIN_PROBE_PIN
     #if (digitalPinToInterrupt(Z_MIN_PROBE_PIN) != NOT_AN_INTERRUPT)
       _ATTACH(Z_MIN_PROBE_PIN);

Marlin/src/HAL/HAL_DUE/endstop_interrupts.h

@@ -77,6 +77,12 @@ void setup_endstop_interrupts() {
   #if HAS_Z3_MIN
     _ATTACH(Z3_MIN_PIN);
   #endif
+  #if HAS_Z4_MAX
+    _ATTACH(Z4_MAX_PIN);
+  #endif
+  #if HAS_Z4_MIN
+    _ATTACH(Z4_MIN_PIN);
+  #endif
   #if HAS_Z_MIN_PROBE_PIN
     _ATTACH(Z_MIN_PROBE_PIN);
   #endif

Marlin/src/HAL/HAL_ESP32/endstop_interrupts.h

@@ -72,6 +72,12 @@ void setup_endstop_interrupts() {
   #if HAS_Z3_MIN
     _ATTACH(Z3_MIN_PIN);
   #endif
+  #if HAS_Z4_MAX
+    _ATTACH(Z4_MAX_PIN);
+  #endif
+  #if HAS_Z4_MIN
+    _ATTACH(Z4_MIN_PIN);
+  #endif
   #if HAS_Z_MIN_PROBE_PIN
     _ATTACH(Z_MIN_PROBE_PIN);
   #endif

Marlin/src/HAL/HAL_LPC1768/endstop_interrupts.h

@@ -93,7 +93,7 @@ void setup_endstop_interrupts() {
     _ATTACH(Z2_MIN_PIN);
   #endif
   #if HAS_Z3_MAX
-    #if !LPC1768_PIN_INTERRUPT_M(Z3_MIN_PIN)
+    #if !LPC1768_PIN_INTERRUPT_M(Z3_MAX_PIN)
       #error "Z3_MIN_PIN is not INTERRUPT-capable."
     #endif
     _ATTACH(Z3_MAX_PIN);
@@ -104,6 +104,18 @@ void setup_endstop_interrupts() {
     #endif
     _ATTACH(Z3_MIN_PIN);
   #endif
+  #if HAS_Z4_MAX
+    #if !LPC1768_PIN_INTERRUPT_M(Z4_MAX_PIN)
+      #error "Z4_MIN_PIN is not INTERRUPT-capable."
+    #endif
+    _ATTACH(Z4_MAX_PIN);
+  #endif
+  #if HAS_Z4_MIN
+    #if !LPC1768_PIN_INTERRUPT_M(Z4_MIN_PIN)
+      #error "Z4_MIN_PIN is not INTERRUPT-capable."
+    #endif
+    _ATTACH(Z4_MIN_PIN);
+  #endif
   #if HAS_Z_MIN_PROBE_PIN
     #if !LPC1768_PIN_INTERRUPT_M(Z_MIN_PROBE_PIN)
       #error "Z_MIN_PROBE_PIN is not INTERRUPT-capable."

Marlin/src/HAL/HAL_SAMD51/endstop_interrupts.h

@@ -98,6 +98,16 @@
 #else
   #define MATCH_Z3_MIN_EILINE(P) false
 #endif
+#if HAS_Z4_MAX
+  #define MATCH_Z4_MAX_EILINE(P) MATCH_EILINE(P, Z4_MAX_PIN)
+#else
+  #define MATCH_Z4_MAX_EILINE(P) false
+#endif
+#if HAS_Z4_MIN
+  #define MATCH_Z4_MIN_EILINE(P) MATCH_EILINE(P, Z4_MIN_PIN)
+#else
+  #define MATCH_Z4_MIN_EILINE(P) false
+#endif
 #if HAS_Z_MIN_PROBE_PIN
   #define MATCH_Z_MIN_PROBE_EILINE(P)   MATCH_EILINE(P, Z_MIN_PROBE_PIN)
 #else
@@ -109,6 +119,7 @@
                                  && !MATCH_Z_MAX_EILINE(P) && !MATCH_Z_MIN_EILINE(P)    \
                                  && !MATCH_Z2_MAX_EILINE(P) && !MATCH_Z2_MIN_EILINE(P)  \
                                  && !MATCH_Z3_MAX_EILINE(P) && !MATCH_Z3_MIN_EILINE(P)  \
+                                 && !MATCH_Z4_MAX_EILINE(P) && !MATCH_Z4_MIN_EILINE(P)  \
                                  && !MATCH_Z_MIN_PROBE_EILINE(P))
 
 // One ISR for all EXT-Interrupts
@@ -117,67 +128,79 @@ void endstop_ISR() { endstops.update(); }
 void setup_endstop_interrupts() {
   #if HAS_X_MAX
     #if !AVAILABLE_EILINE(X_MAX_PIN)
-      static_assert(false, "X_MAX_PIN has no EXTINT line available.");
+      #error "X_MAX_PIN has no EXTINT line available."
     #endif
     attachInterrupt(X_MAX_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_X_MIN
     #if !AVAILABLE_EILINE(X_MIN_PIN)
-      static_assert(false, "X_MIN_PIN has no EXTINT line available.");
+      #error "X_MIN_PIN has no EXTINT line available."
     #endif
     attachInterrupt(X_MIN_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Y_MAX
     #if !AVAILABLE_EILINE(Y_MAX_PIN)
-      static_assert(false, "Y_MAX_PIN has no EXTINT line available.");
+      #error "Y_MAX_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Y_MAX_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Y_MIN
     #if !AVAILABLE_EILINE(Y_MIN_PIN)
-      static_assert(false, "Y_MIN_PIN has no EXTINT line available.");
+      #error "Y_MIN_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Y_MIN_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Z_MAX
     #if !AVAILABLE_EILINE(Z_MAX_PIN)
-      static_assert(false, "Z_MAX_PIN has no EXTINT line available.");
+      #error "Z_MAX_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Z_MAX_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Z_MIN
     #if !AVAILABLE_EILINE(Z_MIN_PIN)
-      static_assert(false, "Z_MIN_PIN has no EXTINT line available.");
+      #error "Z_MIN_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Z_MIN_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Z2_MAX
     #if !AVAILABLE_EILINE(Z2_MAX_PIN)
-      static_assert(false, "Z2_MAX_PIN has no EXTINT line available.");
+      #error "Z2_MAX_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Z2_MAX_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Z2_MIN
     #if !AVAILABLE_EILINE(Z2_MIN_PIN)
-      static_assert(false, "Z2_MIN_PIN has no EXTINT line available.");
+      #error "Z2_MIN_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Z2_MIN_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Z3_MAX
     #if !AVAILABLE_EILINE(Z3_MAX_PIN)
-      static_assert(false, "Z3_MAX_PIN has no EXTINT line available.");
+      #error "Z3_MAX_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Z3_MAX_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Z3_MIN
     #if !AVAILABLE_EILINE(Z3_MIN_PIN)
-      static_assert(false, "Z3_MIN_PIN has no EXTINT line available.");
+      #error "Z3_MIN_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Z3_MIN_PIN, endstop_ISR, CHANGE);
   #endif
+  #if HAS_Z4_MAX
+    #if !AVAILABLE_EILINE(Z4_MAX_PIN)
+      #error "Z4_MAX_PIN has no EXTINT line available."
+    #endif
+    attachInterrupt(Z4_MAX_PIN, endstop_ISR, CHANGE);
+  #endif
+  #if HAS_Z4_MIN
+    #if !AVAILABLE_EILINE(Z4_MIN_PIN)
+      #error "Z4_MIN_PIN has no EXTINT line available."
+    #endif
+    attachInterrupt(Z4_MIN_PIN, endstop_ISR, CHANGE);
+  #endif
   #if HAS_Z_MIN_PROBE_PIN
     #if !AVAILABLE_EILINE(Z_MIN_PROBE_PIN)
-      static_assert(false, "Z_MIN_PROBE_PIN has no EXTINT line available.");
+      #error "Z_MIN_PROBE_PIN has no EXTINT line available."
     #endif
     attachInterrupt(Z_MIN_PROBE_PIN, endstop_ISR, CHANGE);
   #endif

Marlin/src/HAL/HAL_STM32/endstop_interrupts.h

@@ -58,6 +58,12 @@ void setup_endstop_interrupts() {
   #if HAS_Z3_MIN
     attachInterrupt(Z3_MIN_PIN, endstop_ISR, CHANGE);
   #endif
+  #if HAS_Z4_MAX
+    attachInterrupt(Z4_MAX_PIN, endstop_ISR, CHANGE);
+  #endif
+  #if HAS_Z4_MIN
+    attachInterrupt(Z4_MIN_PIN, endstop_ISR, CHANGE);
+  #endif
   #if HAS_Z_MIN_PROBE_PIN
     attachInterrupt(Z_MIN_PROBE_PIN, endstop_ISR, CHANGE);
   #endif

Marlin/src/HAL/HAL_STM32F1/endstop_interrupts.h

@@ -82,6 +82,12 @@ void setup_endstop_interrupts() {
   #endif
   #if HAS_Z3_MIN
     attachInterrupt(Z3_MIN_PIN, endstop_ISR, CHANGE);
+  #endif
+    #if HAS_Z4_MAX
+    attachInterrupt(Z4_MAX_PIN, endstop_ISR, CHANGE);
+  #endif
+  #if HAS_Z4_MIN
+    attachInterrupt(Z4_MIN_PIN, endstop_ISR, CHANGE);
   #endif
   #if HAS_Z_MIN_PROBE_PIN
     attachInterrupt(Z_MIN_PROBE_PIN, endstop_ISR, CHANGE);

Marlin/src/HAL/HAL_STM32_F4_F7/endstop_interrupts.h

@@ -58,6 +58,12 @@ void setup_endstop_interrupts() {
   #if HAS_Z3_MIN
     attachInterrupt(Z3_MIN_PIN, endstop_ISR, CHANGE);
   #endif
+  #if HAS_Z4_MAX
+    attachInterrupt(Z4_MAX_PIN, endstop_ISR, CHANGE);
+  #endif
+  #if HAS_Z4_MIN
+    attachInterrupt(Z4_MIN_PIN, endstop_ISR, CHANGE);
+  #endif
   #if HAS_Z_MIN_PROBE_PIN
     attachInterrupt(Z_MIN_PROBE_PIN, endstop_ISR, CHANGE);
   #endif

Marlin/src/HAL/HAL_TEENSY35_36/endstop_interrupts.h

@@ -76,6 +76,12 @@ void setup_endstop_interrupts() {
   #if HAS_Z3_MIN
     _ATTACH(Z3_MIN_PIN);
   #endif
+  #if HAS_Z4_MAX
+    _ATTACH(Z4_MAX_PIN);
+  #endif
+  #if HAS_Z4_MIN
+    _ATTACH(Z4_MIN_PIN);
+  #endif
   #if HAS_Z_MIN_PROBE_PIN
     _ATTACH(Z_MIN_PROBE_PIN);
   #endif

Marlin/src/core/drivers.h

@@ -63,8 +63,9 @@
   #define AXIS_DRIVER_TYPE_X2(T) false
 #endif
 #define AXIS_DRIVER_TYPE_Y2(T) (ENABLED(Y_DUAL_STEPPER_DRIVERS) && _AXIS_DRIVER_TYPE(Y2,T))
-#define AXIS_DRIVER_TYPE_Z2(T) (Z_MULTI_STEPPER_DRIVERS && _AXIS_DRIVER_TYPE(Z2,T))
+#define AXIS_DRIVER_TYPE_Z2(T) (NUM_Z_STEPPER_DRIVERS >= 2 && _AXIS_DRIVER_TYPE(Z2,T))
-#define AXIS_DRIVER_TYPE_Z3(T) (ENABLED(Z_TRIPLE_STEPPER_DRIVERS) && _AXIS_DRIVER_TYPE(Z3,T))
+#define AXIS_DRIVER_TYPE_Z3(T) (NUM_Z_STEPPER_DRIVERS >= 3 && _AXIS_DRIVER_TYPE(Z3,T))
+#define AXIS_DRIVER_TYPE_Z4(T) (NUM_Z_STEPPER_DRIVERS >= 4 && _AXIS_DRIVER_TYPE(Z4,T))
 #define AXIS_DRIVER_TYPE_E0(T) (E_STEPPERS > 0 && _AXIS_DRIVER_TYPE(E0,T))
 #define AXIS_DRIVER_TYPE_E1(T) (E_STEPPERS > 1 && _AXIS_DRIVER_TYPE(E1,T))
 #define AXIS_DRIVER_TYPE_E2(T) (E_STEPPERS > 2 && _AXIS_DRIVER_TYPE(E2,T))
@@ -80,7 +81,8 @@
 
 #define HAS_DRIVER(T) (    AXIS_DRIVER_TYPE_X(T)  || AXIS_DRIVER_TYPE_X2(T) \
                         || AXIS_DRIVER_TYPE_Y(T)  || AXIS_DRIVER_TYPE_Y2(T) \
-                        || AXIS_DRIVER_TYPE_Z(T)  || AXIS_DRIVER_TYPE_Z2(T) || AXIS_DRIVER_TYPE_Z3(T) \
+                        || AXIS_DRIVER_TYPE_Z(T)  || AXIS_DRIVER_TYPE_Z2(T) \
+                        || AXIS_DRIVER_TYPE_Z3(T) || AXIS_DRIVER_TYPE_Z4(T) \
                         || HAS_E_DRIVER(T) )
 
 // Test for supported TMC drivers that require advanced configuration

Marlin/src/core/language.h

@@ -195,6 +195,8 @@
 #define MSG_Z2_MAX                          "z2_max"
 #define MSG_Z3_MIN                          "z3_min"
 #define MSG_Z3_MAX                          "z3_max"
+#define MSG_Z4_MIN                          "z4_min"
+#define MSG_Z4_MAX                          "z4_max"
 #define MSG_Z_PROBE                         "z_probe"
 #define MSG_FILAMENT_RUNOUT_SENSOR          "filament"
 #define MSG_PROBE_OFFSET                    "Probe Offset"
@@ -333,6 +335,7 @@
 #define MSG_Y2 "Y2"
 #define MSG_Z2 "Z2"
 #define MSG_Z3 "Z3"
+#define MSG_Z4 "Z4"
 
 #define LCD_STR_A MSG_A
 #define LCD_STR_B MSG_B

Marlin/src/feature/controllerfan.cpp

@@ -55,6 +55,9 @@ void controllerfan_update() {
       #if HAS_Z3_ENABLE
         || Z3_ENABLE_READ() == bool(Z_ENABLE_ON)
       #endif
+      #if HAS_Z4_ENABLE
+        || Z4_ENABLE_READ() == bool(Z_ENABLE_ON)
+      #endif
       #if E_STEPPERS
         #define _OR_ENABLED_E(N) || E##N##_ENABLE_READ() == bool(E_ENABLE_ON)
         REPEAT(E_STEPPERS, _OR_ENABLED_E)

Marlin/src/feature/tmc_util.cpp

@@ -387,7 +387,7 @@
       }
       #endif
 
-      #if AXIS_IS_TMC(Z) || AXIS_IS_TMC(Z2) || AXIS_IS_TMC(Z3)
+      #if AXIS_IS_TMC(Z) || AXIS_IS_TMC(Z2) || AXIS_IS_TMC(Z3) || AXIS_IS_TMC(Z4)
       {
         bool result = false;
         #if AXIS_IS_TMC(Z)
@@ -399,6 +399,9 @@
         #if AXIS_IS_TMC(Z3)
           if (monitor_tmc_driver(stepperZ3, need_update_error_counters, need_debug_reporting)) result = true;
         #endif
+        #if AXIS_IS_TMC(Z4)
+          if (monitor_tmc_driver(stepperZ4, need_update_error_counters, need_debug_reporting)) result = true;
+        #endif
         if (result) {
           #if AXIS_IS_TMC(Z)
             step_current_down(stepperZ);
@@ -409,6 +412,9 @@
           #if AXIS_IS_TMC(Z3)
             step_current_down(stepperZ3);
           #endif
+          #if AXIS_IS_TMC(Z4)
+            step_current_down(stepperZ4);
+          #endif
         }
       }
       #endif
@@ -750,6 +756,9 @@
       #if AXIS_IS_TMC(Z3)
         tmc_status(stepperZ3, i);
       #endif
+      #if AXIS_IS_TMC(Z4)
+        tmc_status(stepperZ4, i);
+      #endif
     }
 
     if (print_e) {
@@ -805,6 +814,9 @@
       #if AXIS_IS_TMC(Z3)
         tmc_parse_drv_status(stepperZ3, i);
       #endif
+      #if AXIS_IS_TMC(Z4)
+        tmc_parse_drv_status(stepperZ4, i);
+      #endif
     }
 
     if (print_e) {
@@ -980,6 +992,9 @@
       #if AXIS_IS_TMC(Z3)
         tmc_get_registers(stepperZ3, i);
       #endif
+      #if AXIS_IS_TMC(Z4)
+        tmc_get_registers(stepperZ4, i);
+      #endif
     }
 
     if (print_e) {
@@ -1086,6 +1101,9 @@
     #if AXIS_HAS_SPI(Z3)
       SET_CS_PIN(Z3);
     #endif
+    #if AXIS_HAS_SPI(Z4)
+      SET_CS_PIN(Z4);
+    #endif
     #if AXIS_HAS_SPI(E0)
       SET_CS_PIN(E0);
     #endif
@@ -1160,6 +1178,9 @@ void test_tmc_connection(const bool test_x, const bool test_y, const bool test_z
     #if AXIS_IS_TMC(Z3)
       axis_connection += test_connection(stepperZ3);
     #endif
+    #if AXIS_IS_TMC(Z4)
+      axis_connection += test_connection(stepperZ4);
+    #endif
   }
 
   if (test_e) {

Marlin/src/feature/tmc_util.h

@@ -350,7 +350,7 @@ void test_tmc_connection(const bool test_x, const bool test_y, const bool test_z
 #if USE_SENSORLESS
 
   // Track enabled status of stealthChop and only re-enable where applicable
-  struct sensorless_t { bool x, y, z, x2, y2, z2, z3; };
+  struct sensorless_t { bool x, y, z, x2, y2, z2, z3, z4; };
 
   #if ENABLED(IMPROVE_HOMING_RELIABILITY)
     extern millis_t sg_guard_period;

Marlin/src/gcode/calibrate/G34_M422.cpp

@@ -52,20 +52,22 @@ constexpr xy_pos_t test_z_stepper_align_xy[] = Z_STEPPER_ALIGN_XY;
 
 #if ENABLED(Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS)
 
-  static_assert(COUNT(test_z_stepper_align_xy) >= Z_STEPPER_COUNT,
+  static_assert(COUNT(test_z_stepper_align_xy) >= NUM_Z_STEPPER_DRIVERS,
     "Z_STEPPER_ALIGN_XY requires at least three {X,Y} entries (Z, Z2, Z3, ...)."
   );
 
   constexpr float test_z_stepper_align_stepper_xy[][XY] = Z_STEPPER_ALIGN_STEPPER_XY;
   static_assert(
-    COUNT(test_z_stepper_align_stepper_xy) == Z_STEPPER_COUNT,
+    COUNT(test_z_stepper_align_stepper_xy) == NUM_Z_STEPPER_DRIVERS,
     "Z_STEPPER_ALIGN_STEPPER_XY requires three {X,Y} entries (one per Z stepper)."
   );
 
 #else
 
-  static_assert(COUNT(test_z_stepper_align_xy) == Z_STEPPER_COUNT,
+  static_assert(COUNT(test_z_stepper_align_xy) == NUM_Z_STEPPER_DRIVERS,
-    #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+    #if NUM_Z_STEPPER_DRIVERS == 4
+      "Z_STEPPER_ALIGN_XY requires four {X,Y} entries (Z, Z2, Z3, and Z4)."
+    #elif NUM_Z_STEPPER_DRIVERS == 3
       "Z_STEPPER_ALIGN_XY requires three {X,Y} entries (Z, Z2, and Z3)."
     #else
       "Z_STEPPER_ALIGN_XY requires two {X,Y} entries (Z and Z2)."
@@ -85,10 +87,13 @@ static_assert(LTEST(0) && RTEST(0), "The 1st Z_STEPPER_ALIGN_XY X is unreachable
 static_assert(FTEST(0) && BTEST(0), "The 1st Z_STEPPER_ALIGN_XY Y is unreachable with the default probe Y offset.");
 static_assert(LTEST(1) && RTEST(1), "The 2nd Z_STEPPER_ALIGN_XY X is unreachable with the default probe X offset.");
 static_assert(FTEST(1) && BTEST(1), "The 2nd Z_STEPPER_ALIGN_XY Y is unreachable with the default probe Y offset.");
-
+#if NUM_Z_STEPPER_DRIVERS >= 3
-#if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
   static_assert(LTEST(2) && RTEST(2), "The 3rd Z_STEPPER_ALIGN_XY X is unreachable with the default probe X offset.");
   static_assert(FTEST(2) && BTEST(2), "The 3rd Z_STEPPER_ALIGN_XY Y is unreachable with the default probe Y offset.");
+  #if NUM_Z_STEPPER_DRIVERS >= 4
+    static_assert(LTEST(3) && RTEST(3), "The 4th Z_STEPPER_ALIGN_XY X is unreachable with the default probe X offset.");
+    static_assert(FTEST(3) && BTEST(3), "The 4th Z_STEPPER_ALIGN_XY Y is unreachable with the default probe Y offset.");
+  #endif
 #endif
 
 //
@@ -105,8 +110,11 @@ static xy_pos_t z_stepper_align_pos[] = Z_STEPPER_ALIGN_XY;
 inline void set_all_z_lock(const bool lock) {
   stepper.set_z_lock(lock);
   stepper.set_z2_lock(lock);
-  #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+  #if NUM_Z_STEPPER_DRIVERS >= 3
     stepper.set_z3_lock(lock);
+    #if NUM_Z_STEPPER_DRIVERS >= 4
+      stepper.set_z4_lock(lock);
+    #endif
   #endif
 }
 
@@ -125,6 +133,11 @@ void GcodeSuite::G34() {
 
   do { // break out on error
 
+    #if NUM_Z_STEPPER_DRIVERS == 4
+      SERIAL_ECHOLNPGM("Quad Z Stepper Leveling not Yet Supported");
+      break;
+    #endif
+
     const int8_t z_auto_align_iterations = parser.intval('I', Z_STEPPER_ALIGN_ITERATIONS);
     if (!WITHIN(z_auto_align_iterations, 1, 30)) {
       SERIAL_ECHOLNPGM("?(I)teration out of bounds (1-30).");
@@ -187,7 +200,7 @@ void GcodeSuite::G34() {
     // Compute a worst-case clearance height to probe from. After the first
     // iteration this will be re-calculated based on the actual bed position
     float z_probe = Z_BASIC_CLEARANCE + (G34_MAX_GRADE) * 0.01f * (
-      #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+      #if NUM_Z_STEPPER_DRIVERS == 3
          SQRT(_MAX(HYPOT2(z_stepper_align_pos[0].x - z_stepper_align_pos[0].y, z_stepper_align_pos[1].x - z_stepper_align_pos[1].y),
                    HYPOT2(z_stepper_align_pos[1].x - z_stepper_align_pos[1].y, z_stepper_align_pos[2].x - z_stepper_align_pos[2].y),
                    HYPOT2(z_stepper_align_pos[2].x - z_stepper_align_pos[2].y, z_stepper_align_pos[0].x - z_stepper_align_pos[0].y)))
@@ -202,7 +215,7 @@ void GcodeSuite::G34() {
     // Move the Z coordinate realm towards the positive - dirty trick
     current_position.z -= z_probe * 0.5f;
 
-    float last_z_align_move[Z_STEPPER_COUNT] = ARRAY_N(Z_STEPPER_COUNT, 10000.0f, 10000.0f, 10000.0f),
+    float last_z_align_move[NUM_Z_STEPPER_DRIVERS] = ARRAY_N(NUM_Z_STEPPER_DRIVERS, 10000.0f, 10000.0f, 10000.0f),
           z_measured[G34_PROBE_COUNT] = { 0 },
           z_maxdiff = 0.0f,
           amplification = z_auto_align_amplification;
@@ -273,7 +286,7 @@ void GcodeSuite::G34() {
         finish_incremental_LSF(&lfd);
 
         z_measured_min = 100000.0f;
-        for (uint8_t i = 0; i < Z_STEPPER_COUNT; ++i) {
+        for (uint8_t i = 0; i < NUM_Z_STEPPER_DRIVERS; ++i) {
           z_measured[i] = -(lfd.A * z_stepper_align_stepper_pos[i].x + lfd.B * z_stepper_align_stepper_pos[i].y);
           z_measured_min = _MIN(z_measured_min, z_measured[i]);
         }
@@ -283,7 +296,7 @@ void GcodeSuite::G34() {
 
       SERIAL_ECHOLNPAIR("\n"
         "DIFFERENCE Z1-Z2=", ABS(z_measured[0] - z_measured[1])
-        #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+        #if NUM_Z_STEPPER_DRIVERS == 3
           , " Z2-Z3=", ABS(z_measured[1] - z_measured[2])
           , " Z3-Z1=", ABS(z_measured[2] - z_measured[0])
         #endif
@@ -294,7 +307,7 @@ void GcodeSuite::G34() {
 
       bool success_break = true;
       // Correct the individual stepper offsets
-      for (uint8_t zstepper = 0; zstepper < Z_STEPPER_COUNT; ++zstepper) {
+      for (uint8_t zstepper = 0; zstepper < NUM_Z_STEPPER_DRIVERS; ++zstepper) {
         // Calculate current stepper move
         const float z_align_move = z_measured[zstepper] - z_measured_min,
                     z_align_abs = ABS(z_align_move);
@@ -324,7 +337,7 @@ void GcodeSuite::G34() {
         switch (zstepper) {
           case 0: stepper.set_z_lock(false); break;
           case 1: stepper.set_z2_lock(false); break;
-          #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+          #if NUM_Z_STEPPER_DRIVERS == 3
             case 2: stepper.set_z3_lock(false); break;
           #endif
         }
@@ -397,7 +410,7 @@ void GcodeSuite::M422() {
     for (uint8_t i = 0; i < G34_PROBE_COUNT; ++i)
       SERIAL_ECHOLNPAIR_P(PSTR("M422 S"), i + 1, SP_X_STR, z_stepper_align_pos[i].x, SP_Y_STR, z_stepper_align_pos[i].y);
     #if ENABLED(Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS)
-      for (uint8_t i = 0; i < Z_STEPPER_COUNT; ++i)
+      for (uint8_t i = 0; i < NUM_Z_STEPPER_DRIVERS; ++i)
         SERIAL_ECHOLNPAIR_P(PSTR("M422 W"), i + 1, SP_X_STR, z_stepper_align_stepper_pos[i].x, SP_Y_STR, z_stepper_align_stepper_pos[i].y);
     #endif
     return;
@@ -446,7 +459,7 @@ void GcodeSuite::M422() {
   else {
     #if ENABLED(Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS)
       position_index = parser.intval('W') - 1;
-      if (!WITHIN(position_index, 0, Z_STEPPER_COUNT - 1)) {
+      if (!WITHIN(position_index, 0, NUM_Z_STEPPER_DRIVERS - 1)) {
         SERIAL_ECHOLNPGM("?(W) Z-Stepper index invalid.");
         return;
       }

Marlin/src/gcode/calibrate/M666.cpp

@@ -57,10 +57,11 @@
    * M666: Set Dual Endstops offsets for X, Y, and/or Z.
    *       With no parameters report current offsets.
    *
-   * For Triple Z Endstops:
+   * For Triple / Quad Z Endstops:
    *   Set Z2 Only: M666 S2 Z<offset>
    *   Set Z3 Only: M666 S3 Z<offset>
-   *      Set Both: M666 Z<offset>
+   *   Set Z4 Only: M666 S4 Z<offset>
+   *       Set All: M666 Z<offset>
    */
   void GcodeSuite::M666() {
     #if ENABLED(X_DUAL_ENDSTOPS)
@@ -69,15 +70,20 @@
     #if ENABLED(Y_DUAL_ENDSTOPS)
       if (parser.seenval('Y')) endstops.y2_endstop_adj = parser.value_linear_units();
     #endif
-    #if ENABLED(Z_TRIPLE_ENDSTOPS)
+    #if ENABLED(Z_MULTI_ENDSTOPS)
       if (parser.seenval('Z')) {
+        #if NUM_Z_STEPPER_DRIVERS >= 3
           const float z_adj = parser.value_linear_units();
           const int ind = parser.intval('S');
           if (!ind || ind == 2) endstops.z2_endstop_adj = z_adj;
           if (!ind || ind == 3) endstops.z3_endstop_adj = z_adj;
+          #if NUM_Z_STEPPER_DRIVERS >= 4
+            if (!ind || ind == 4) endstops.z4_endstop_adj = z_adj;
+          #endif
+        #else
+          endstops.z2_endstop_adj = parser.value_linear_units();
+        #endif
       }
-    #elif Z_MULTI_ENDSTOPS
-      if (parser.seen('Z')) endstops.z2_endstop_adj = parser.value_linear_units();
     #endif
     if (!parser.seen("XYZ")) {
       SERIAL_ECHOPGM("Dual Endstop Adjustment (mm): ");
@@ -87,11 +93,14 @@
       #if ENABLED(Y_DUAL_ENDSTOPS)
         SERIAL_ECHOPAIR(" Y2:", endstops.y2_endstop_adj);
       #endif
-      #if Z_MULTI_ENDSTOPS
+      #if ENABLED(Z_MULTI_ENDSTOPS)
         SERIAL_ECHOPAIR(" Z2:", endstops.z2_endstop_adj);
-      #endif
+        #if NUM_Z_STEPPER_DRIVERS >= 3
-      #if ENABLED(Z_TRIPLE_ENDSTOPS)
           SERIAL_ECHOPAIR(" Z3:", endstops.z3_endstop_adj);
+          #if NUM_Z_STEPPER_DRIVERS >= 4
+            SERIAL_ECHOPAIR(" Z4:", endstops.z4_endstop_adj);
+          #endif
+        #endif
       #endif
       SERIAL_EOL();
     }

Marlin/src/gcode/feature/L6470/M122.cpp

@@ -115,6 +115,9 @@ void GcodeSuite::M122() {
   #if AXIS_IS_L64XX(Z3)
     L6470_say_status(Z3);
   #endif
+  #if AXIS_IS_L64XX(Z4)
+    L6470_say_status(Z4);
+  #endif
   #if AXIS_IS_L64XX(E0)
     L6470_say_status(E0);
   #endif

Marlin/src/gcode/feature/L6470/M906.cpp

@@ -44,7 +44,7 @@
  *     1 - monitor only X, Y, Z or E1
  *     2 - monitor only X2, Y2, Z2 or E2
  *     3 - monitor only Z3 or E3
- *     4 - monitor only E4
+ *     4 - monitor only Z4 or E4
  *     5 - monitor only E5
  * Xxxx, Yxxx, Zxxx, Exxx - axis to change (optional)
  *     L6474 - current in mA (4A max)
@@ -274,6 +274,9 @@ void GcodeSuite::M906() {
         #if AXIS_IS_L64XX(Z3)
           if (index == 2) L6470_SET_KVAL_HOLD(Z3);
         #endif
+        #if AXIS_DRIVER_TYPE_Z4(L6470)
+          if (index == 3) L6470_SET_KVAL_HOLD(Z4);
+        #endif
         break;
       case E_AXIS: {
         const int8_t target_extruder = get_target_extruder_from_command();
@@ -328,6 +331,9 @@ void GcodeSuite::M906() {
     #if AXIS_IS_L64XX(Z3)
       L64XX_REPORT_CURRENT(Z3);
     #endif
+    #if AXIS_IS_L64XX(Z4)
+      L64XX_REPORT_CURRENT(Z4);
+    #endif
     #if AXIS_IS_L64XX(E0)
       L64XX_REPORT_CURRENT(E0);
     #endif

Marlin/src/gcode/feature/L6470/M916-918.cpp

@@ -46,6 +46,7 @@
  *     1 - monitor only X, Y, Z, E1
  *     2 - monitor only X2, Y2, Z2, E2
  *     3 - monitor only Z3, E3
+ *     4 - monitor only Z4, E4
  *
  * Xxxx, Yxxx, Zxxx, Exxx - axis to be monitored with displacement
  *     xxx (1-255) is distance moved on either side of current position

Marlin/src/gcode/feature/trinamic/M569.cpp

@@ -46,7 +46,8 @@ static void set_stealth_status(const bool enable, const int8_t target_extruder)
 
   #if    AXIS_HAS_STEALTHCHOP(X)  || AXIS_HAS_STEALTHCHOP(X2) \
       || AXIS_HAS_STEALTHCHOP(Y)  || AXIS_HAS_STEALTHCHOP(Y2) \
-      || AXIS_HAS_STEALTHCHOP(Z) || AXIS_HAS_STEALTHCHOP(Z2) || AXIS_HAS_STEALTHCHOP(Z3)
+      || AXIS_HAS_STEALTHCHOP(Z)  || AXIS_HAS_STEALTHCHOP(Z2) \
+      || AXIS_HAS_STEALTHCHOP(Z3) || AXIS_HAS_STEALTHCHOP(Z4)
     const uint8_t index = parser.byteval('I');
   #endif
 
@@ -78,6 +79,9 @@ static void set_stealth_status(const bool enable, const int8_t target_extruder)
         #if AXIS_HAS_STEALTHCHOP(Z3)
           if (index == 2) TMC_SET_STEALTH(Z3);
         #endif
+        #if AXIS_HAS_STEALTHCHOP(Z4)
+          if (index == 3) TMC_SET_STEALTH(Z4);
+        #endif
         break;
       case E_AXIS: {
         if (target_extruder < 0) return;
@@ -130,6 +134,9 @@ static void say_stealth_status() {
   #if AXIS_HAS_STEALTHCHOP(Z3)
     TMC_SAY_STEALTH_STATUS(Z3);
   #endif
+  #if AXIS_HAS_STEALTHCHOP(Z4)
+    TMC_SAY_STEALTH_STATUS(Z4);
+  #endif
   #if AXIS_HAS_STEALTHCHOP(E0)
     TMC_SAY_STEALTH_STATUS(E0);
   #endif

Marlin/src/gcode/feature/trinamic/M906.cpp

@@ -37,7 +37,7 @@
  *   Z[current]  - Set mA current for Z driver(s)
  *   E[current]  - Set mA current for E driver(s)
  *
- *   I[index]    - Axis sub-index (Omit or 0 for X, Y, Z; 1 for X2, Y2, Z2; 2 for Z3.)
+ *   I[index]    - Axis sub-index (Omit or 0 for X, Y, Z; 1 for X2, Y2, Z2; 2 for Z3; 3 for Z4.)
  *   T[index]    - Extruder index (Zero-based. Omit for E0 only.)
  *
  * With no parameters report driver currents.
@@ -48,7 +48,7 @@ void GcodeSuite::M906() {
 
   bool report = true;
 
-  #if AXIS_IS_TMC(X) || AXIS_IS_TMC(X2) || AXIS_IS_TMC(Y) || AXIS_IS_TMC(Y2) || AXIS_IS_TMC(Z) || AXIS_IS_TMC(Z2) || AXIS_IS_TMC(Z3)
+  #if AXIS_IS_TMC(X) || AXIS_IS_TMC(X2) || AXIS_IS_TMC(Y) || AXIS_IS_TMC(Y2) || AXIS_IS_TMC(Z) || AXIS_IS_TMC(Z2) || AXIS_IS_TMC(Z3) || AXIS_IS_TMC(Z4)
     const uint8_t index = parser.byteval('I');
   #endif
 
@@ -81,6 +81,9 @@ void GcodeSuite::M906() {
         #if AXIS_IS_TMC(Z3)
           if (index == 2) TMC_SET_CURRENT(Z3);
         #endif
+        #if AXIS_IS_TMC(Z4)
+          if (index == 3) TMC_SET_CURRENT(Z4);
+        #endif
         break;
       case E_AXIS: {
         const int8_t target_extruder = get_target_extruder_from_command();
@@ -131,6 +134,9 @@ void GcodeSuite::M906() {
     #if AXIS_IS_TMC(Z3)
       TMC_SAY_CURRENT(Z3);
     #endif
+    #if AXIS_IS_TMC(Z4)
+      TMC_SAY_CURRENT(Z4);
+    #endif
     #if AXIS_IS_TMC(E0)
       TMC_SAY_CURRENT(E0);
     #endif

Marlin/src/gcode/feature/trinamic/M911-M914.cpp

@@ -37,7 +37,7 @@
 
   #define M91x_SOME_X (M91x_USE(X) || M91x_USE(X2))
   #define M91x_SOME_Y (M91x_USE(Y) || M91x_USE(Y2))
-  #define M91x_SOME_Z (M91x_USE(Z) || M91x_USE(Z2) || M91x_USE(Z3))
+  #define M91x_SOME_Z (M91x_USE(Z) || M91x_USE(Z2) || M91x_USE(Z3) || M91x_USE(Z4))
   #define M91x_SOME_E (M91x_USE_E(0) || M91x_USE_E(1) || M91x_USE_E(2) || M91x_USE_E(3) || M91x_USE_E(4) || M91x_USE_E(5))
 
   #if !M91x_SOME_X && !M91x_SOME_Y && !M91x_SOME_Z && !M91x_SOME_E
@@ -70,6 +70,9 @@
     #if M91x_USE(Z3)
       tmc_report_otpw(stepperZ3);
     #endif
+    #if M91x_USE(Z4)
+      tmc_report_otpw(stepperZ4);
+    #endif
     #if M91x_USE_E(0)
       tmc_report_otpw(stepperE0);
     #endif
@@ -92,7 +95,7 @@
 
   /**
    * M912: Clear TMC stepper driver overtemperature pre-warn flag held by the library
-   *       Specify one or more axes with X, Y, Z, X1, Y1, Z1, X2, Y2, Z2, Z3 and E[index].
+   *       Specify one or more axes with X, Y, Z, X1, Y1, Z1, X2, Y2, Z2, Z3, Z4 and E[index].
    *       If no axes are given, clear all.
    *
    * Examples:
@@ -160,6 +163,9 @@
       #if M91x_USE(Z3)
         if (hasNone || zval == 3 || (hasZ && zval < 0)) tmc_clear_otpw(stepperZ3);
       #endif
+      #if M91x_USE(Z4)
+        if (hasNone || zval == 4 || (hasZ && zval < 0)) tmc_clear_otpw(stepperZ4);
+      #endif
     #endif
 
     #if M91x_SOME_E
@@ -198,7 +204,7 @@
     #define TMC_SET_PWMTHRS_E(E) stepperE##E.set_pwm_thrs(value)
 
     bool report = true;
-    #if AXIS_IS_TMC(X) || AXIS_IS_TMC(X2) || AXIS_IS_TMC(Y) || AXIS_IS_TMC(Y2) || AXIS_IS_TMC(Z) || AXIS_IS_TMC(Z2) || AXIS_IS_TMC(Z3)
+    #if AXIS_IS_TMC(X) || AXIS_IS_TMC(X2) || AXIS_IS_TMC(Y) || AXIS_IS_TMC(Y2) || AXIS_IS_TMC(Z) || AXIS_IS_TMC(Z2) || AXIS_IS_TMC(Z3) || AXIS_IS_TMC(Z4)
       const uint8_t index = parser.byteval('I');
     #endif
     LOOP_XYZE(i) if (int32_t value = parser.longval(axis_codes[i])) {
@@ -230,6 +236,9 @@
           #if AXIS_HAS_STEALTHCHOP(Z3)
             if (index == 0 || index == 3) TMC_SET_PWMTHRS(Z,Z3);
           #endif
+          #if AXIS_HAS_STEALTHCHOP(Z4)
+            if (index == 0 || index == 4) TMC_SET_PWMTHRS(Z,Z4);
+          #endif
           break;
         case E_AXIS: {
           #if E_STEPPERS
@@ -282,6 +291,9 @@
       #if AXIS_HAS_STEALTHCHOP(Z3)
         TMC_SAY_PWMTHRS(Z,Z3);
       #endif
+      #if AXIS_HAS_STEALTHCHOP(Z4)
+        TMC_SAY_PWMTHRS(Z,Z4);
+      #endif
       #if E_STEPPERS && AXIS_HAS_STEALTHCHOP(E0)
         TMC_SAY_PWMTHRS_E(0);
       #endif
@@ -347,6 +359,9 @@
             #if AXIS_HAS_STALLGUARD(Z3)
               if (index == 0 || index == 3) stepperZ3.homing_threshold(value);
             #endif
+            #if AXIS_HAS_STALLGUARD(Z4)
+              if (index == 0 || index == 4) stepperZ4.homing_threshold(value);
+            #endif
             break;
         #endif
       }
@@ -379,6 +394,9 @@
         #if AXIS_HAS_STALLGUARD(Z3)
           tmc_print_sgt(stepperZ3);
         #endif
+        #if AXIS_HAS_STALLGUARD(Z4)
+          tmc_print_sgt(stepperZ4);
+        #endif
       #endif
     }
   }

Marlin/src/gcode/gcode.cpp

@@ -566,8 +566,8 @@ void GcodeSuite::process_parsed_command(const bool no_ok/*=false*/) {
         case 665: M665(); break;                                  // M665: Set delta configurations
       #endif
 
-      #if ANY(DELTA, X_DUAL_ENDSTOPS, Y_DUAL_ENDSTOPS, Z_DUAL_ENDSTOPS)
+      #if ENABLED(DELTA) || HAS_EXTRA_ENDSTOPS
-        case 666: M666(); break;                                  // M666: Set delta or dual endstop adjustment
+        case 666: M666(); break;                                  // M666: Set delta or multiple endstop adjustment
       #endif
 
       #if ENABLED(FWRETRACT)

Marlin/src/gcode/host/M114.cpp

@@ -121,6 +121,9 @@
       #if AXIS_IS_L64XX(Z3)
         REPORT_ABSOLUTE_POS(Z3);
       #endif
+      #if AXIS_IS_L64XX(Z4)
+        REPORT_ABSOLUTE_POS(Z4);
+      #endif
       #if AXIS_IS_L64XX(E0)
         REPORT_ABSOLUTE_POS(E0);
       #endif

Marlin/src/inc/Conditionals_LCD.h

@@ -526,6 +526,7 @@
   #define GRID_MAX_POINTS ((GRID_MAX_POINTS_X) * (GRID_MAX_POINTS_Y))
 #endif
 
+#define HAS_EXTRA_ENDSTOPS           ANY(X_DUAL_ENDSTOPS, Y_DUAL_ENDSTOPS, Z_MULTI_ENDSTOPS)
 #define HAS_SOFTWARE_ENDSTOPS        EITHER(MIN_SOFTWARE_ENDSTOPS, MAX_SOFTWARE_ENDSTOPS)
 #define HAS_RESUME_CONTINUE          ANY(EXTENSIBLE_UI, NEWPANEL, EMERGENCY_PARSER)
 #define HAS_COLOR_LEDS               ANY(BLINKM, RGB_LED, RGBW_LED, PCA9632, PCA9533, NEOPIXEL_LED)
@@ -535,10 +536,6 @@
 #define HAS_SERVICE_INTERVALS        (ENABLED(PRINTCOUNTER) && (SERVICE_INTERVAL_1 > 0 || SERVICE_INTERVAL_2 > 0 || SERVICE_INTERVAL_3 > 0))
 #define HAS_FILAMENT_SENSOR          ENABLED(FILAMENT_RUNOUT_SENSOR)
 
-#define Z_MULTI_STEPPER_DRIVERS EITHER(Z_DUAL_STEPPER_DRIVERS, Z_TRIPLE_STEPPER_DRIVERS)
-#define Z_MULTI_ENDSTOPS        EITHER(Z_DUAL_ENDSTOPS, Z_TRIPLE_ENDSTOPS)
-#define HAS_EXTRA_ENDSTOPS     (EITHER(X_DUAL_ENDSTOPS, Y_DUAL_ENDSTOPS) || Z_MULTI_ENDSTOPS)
-
 #define HAS_GAMES     ANY(MARLIN_BRICKOUT, MARLIN_INVADERS, MARLIN_SNAKE, MARLIN_MAZE)
 #define HAS_GAME_MENU (1 < ENABLED(MARLIN_BRICKOUT) + ENABLED(MARLIN_INVADERS) + ENABLED(MARLIN_SNAKE) + ENABLED(MARLIN_MAZE))
 

Marlin/src/inc/Conditionals_adv.h

@@ -54,6 +54,11 @@
   #undef SHOW_TEMP_ADC_VALUES
 #endif
 
+// Multiple Z steppers
+#ifndef NUM_Z_STEPPER_DRIVERS
+  #define NUM_Z_STEPPER_DRIVERS 1
+#endif
+
 #define HAS_CUTTER EITHER(SPINDLE_FEATURE, LASER_FEATURE)
 
 #if !defined(__AVR__) || !defined(USBCON)

Marlin/src/inc/Conditionals_post.h

@@ -687,9 +687,6 @@
   #endif
 #endif
 
-// Is an endstop plug used for the X2 endstop?
-#define IS_X2_ENDSTOP(A,M) (ENABLED(X_DUAL_ENDSTOPS) && X2_USE_ENDSTOP == _##A##M##_)
-
 /**
  * Y_DUAL_ENDSTOPS endstop reassignment
  */
@@ -743,13 +740,11 @@
   #endif
 #endif
 
-// Is an endstop plug used for the Y2 endstop or the bed probe?
-#define IS_Y2_ENDSTOP(A,M) (ENABLED(Y_DUAL_ENDSTOPS) && Y2_USE_ENDSTOP == _##A##M##_)
-
 /**
- * Z_DUAL_ENDSTOPS endstop reassignment
+ * Z_MULTI_ENDSTOPS endstop reassignment
  */
-#if Z_MULTI_ENDSTOPS
+#if ENABLED(Z_MULTI_ENDSTOPS)
+
   #if Z_HOME_DIR > 0
     #if Z2_USE_ENDSTOP == _XMIN_
       #define Z2_MAX_ENDSTOP_INVERTING X_MIN_ENDSTOP_INVERTING
@@ -797,9 +792,8 @@
     #endif
     #define Z2_MAX_ENDSTOP_INVERTING false
   #endif
-#endif
 
-#if ENABLED(Z_TRIPLE_ENDSTOPS)
+  #if NUM_Z_STEPPER_DRIVERS >= 3
     #if Z_HOME_DIR > 0
       #if Z3_USE_ENDSTOP == _XMIN_
         #define Z3_MAX_ENDSTOP_INVERTING X_MIN_ENDSTOP_INVERTING
@@ -847,17 +841,59 @@
       #endif
       #define Z3_MAX_ENDSTOP_INVERTING false
     #endif
-#endif
+  #endif
 
-// Is an endstop plug used for the Z2 endstop or the bed probe?
+  #if NUM_Z_STEPPER_DRIVERS >= 4
-#define IS_Z2_OR_PROBE(A,M) ( \
+    #if Z_HOME_DIR > 0
-     (Z_MULTI_ENDSTOPS && Z2_USE_ENDSTOP == _##A##M##_) \
+      #if Z4_USE_ENDSTOP == _XMIN_
-  || (HAS_CUSTOM_PROBE_PIN && Z_MIN_PROBE_PIN == A##_##M##_PIN ) )
+        #define Z4_MAX_ENDSTOP_INVERTING X_MIN_ENDSTOP_INVERTING
+        #define Z4_MAX_PIN X_MIN_PIN
+      #elif Z4_USE_ENDSTOP == _XMAX_
+        #define Z4_MAX_ENDSTOP_INVERTING X_MAX_ENDSTOP_INVERTING
+        #define Z4_MAX_PIN X_MAX_PIN
+      #elif Z4_USE_ENDSTOP == _YMIN_
+        #define Z4_MAX_ENDSTOP_INVERTING Y_MIN_ENDSTOP_INVERTING
+        #define Z4_MAX_PIN Y_MIN_PIN
+      #elif Z4_USE_ENDSTOP == _YMAX_
+        #define Z4_MAX_ENDSTOP_INVERTING Y_MAX_ENDSTOP_INVERTING
+        #define Z4_MAX_PIN Y_MAX_PIN
+      #elif Z4_USE_ENDSTOP == _ZMIN_
+        #define Z4_MAX_ENDSTOP_INVERTING Z_MIN_ENDSTOP_INVERTING
+        #define Z4_MAX_PIN Z_MIN_PIN
+      #elif Z4_USE_ENDSTOP == _ZMAX_
+        #define Z4_MAX_ENDSTOP_INVERTING Z_MAX_ENDSTOP_INVERTING
+        #define Z4_MAX_PIN Z_MAX_PIN
+      #else
+        #define Z4_MAX_ENDSTOP_INVERTING false
+      #endif
+      #define Z4_MIN_ENDSTOP_INVERTING false
+    #else
+      #if Z4_USE_ENDSTOP == _XMIN_
+        #define Z4_MIN_ENDSTOP_INVERTING X_MIN_ENDSTOP_INVERTING
+        #define Z4_MIN_PIN X_MIN_PIN
+      #elif Z4_USE_ENDSTOP == _XMAX_
+        #define Z4_MIN_ENDSTOP_INVERTING X_MAX_ENDSTOP_INVERTING
+        #define Z4_MIN_PIN X_MAX_PIN
+      #elif Z4_USE_ENDSTOP == _YMIN_
+        #define Z4_MIN_ENDSTOP_INVERTING Y_MIN_ENDSTOP_INVERTING
+        #define Z4_MIN_PIN Y_MIN_PIN
+      #elif Z4_USE_ENDSTOP == _YMAX_
+        #define Z4_MIN_ENDSTOP_INVERTING Y_MAX_ENDSTOP_INVERTING
+        #define Z4_MIN_PIN Y_MAX_PIN
+      #elif Z4_USE_ENDSTOP == _ZMIN_
+        #define Z4_MIN_ENDSTOP_INVERTING Z_MIN_ENDSTOP_INVERTING
+        #define Z4_MIN_PIN Z_MIN_PIN
+      #elif Z4_USE_ENDSTOP == _ZMAX_
+        #define Z4_MIN_ENDSTOP_INVERTING Z_MAX_ENDSTOP_INVERTING
+        #define Z4_MIN_PIN Z_MAX_PIN
+      #else
+        #define Z4_MIN_ENDSTOP_INVERTING false
+      #endif
+      #define Z4_MAX_ENDSTOP_INVERTING false
+    #endif
+  #endif
 
-// Is an endstop plug used for the Z3 endstop or the bed probe?
+#endif // Z_MULTI_ENDSTOPS
-#define IS_Z3_OR_PROBE(A,M) ( \
-     (ENABLED(Z_TRIPLE_ENDSTOPS) && Z3_USE_ENDSTOP == _##A##M##_) \
-  || (HAS_CUSTOM_PROBE_PIN && Z_MIN_PROBE_PIN == A##_##M##_PIN ) )
 
 /**
  * Set ENDSTOPPULLUPS for active endstop switches
@@ -947,6 +983,11 @@
 #define HAS_Z3_STEP       (PIN_EXISTS(Z3_STEP))
 #define HAS_Z3_MICROSTEPS (PIN_EXISTS(Z3_MS1))
 
+#define HAS_Z4_ENABLE     (PIN_EXISTS(Z4_ENABLE) || (ENABLED(SOFTWARE_DRIVER_ENABLE) && AXIS_IS_TMC(Z4)))
+#define HAS_Z4_DIR        (PIN_EXISTS(Z4_DIR))
+#define HAS_Z4_STEP       (PIN_EXISTS(Z4_STEP))
+#define HAS_Z4_MICROSTEPS (PIN_EXISTS(Z4_MS1))
+
 // Extruder steppers and solenoids
 #define HAS_E0_ENABLE     (PIN_EXISTS(E0_ENABLE) || (ENABLED(SOFTWARE_DRIVER_ENABLE) && AXIS_IS_TMC(E0)))
 #define HAS_E0_DIR        (PIN_EXISTS(E0_DIR))
@@ -999,6 +1040,7 @@
   #define Z_SENSORLESS  (AXIS_HAS_STALLGUARD(Z)  && defined(Z_STALL_SENSITIVITY))
   #define Z2_SENSORLESS (AXIS_HAS_STALLGUARD(Z2) && defined(Z2_STALL_SENSITIVITY))
   #define Z3_SENSORLESS (AXIS_HAS_STALLGUARD(Z3) && defined(Z3_STALL_SENSITIVITY))
+  #define Z4_SENSORLESS (AXIS_HAS_STALLGUARD(Z4) && defined(Z4_STALL_SENSITIVITY))
   #if ENABLED(SPI_ENDSTOPS)
     #define X_SPI_SENSORLESS X_SENSORLESS
     #define Y_SPI_SENSORLESS Y_SENSORLESS
@@ -1011,8 +1053,19 @@
     && E0_ENABLE_PIN != Y_ENABLE_PIN && E1_ENABLE_PIN != Y_ENABLE_PIN ) \
 )
 
+//
 // Endstops and bed probe
-#define _HAS_STOP(A,M) (PIN_EXISTS(A##_##M) && !IS_X2_ENDSTOP(A,M) && !IS_Y2_ENDSTOP(A,M) && !IS_Z2_OR_PROBE(A,M))
+//
+
+// Is an endstop plug used for extra Z endstops or the probe?
+#define IS_PROBE_PIN(A,M) (HAS_CUSTOM_PROBE_PIN && Z_MIN_PROBE_PIN == P)
+#define IS_X2_ENDSTOP(A,M) (ENABLED(X_DUAL_ENDSTOPS) && X2_USE_ENDSTOP == _##A##M##_)
+#define IS_Y2_ENDSTOP(A,M) (ENABLED(Y_DUAL_ENDSTOPS) && Y2_USE_ENDSTOP == _##A##M##_)
+#define IS_Z2_ENDSTOP(A,M) (ENABLED(Z_MULTI_ENDSTOPS) && Z2_USE_ENDSTOP == _##A##M##_)
+#define IS_Z3_ENDSTOP(A,M) (ENABLED(Z_MULTI_ENDSTOPS) && NUM_Z_STEPPER_DRIVERS >= 3 && Z3_USE_ENDSTOP == _##A##M##_)
+#define IS_Z4_ENDSTOP(A,M) (ENABLED(Z_MULTI_ENDSTOPS) && NUM_Z_STEPPER_DRIVERS >= 4 && Z4_USE_ENDSTOP == _##A##M##_)
+
+#define _HAS_STOP(A,M) (PIN_EXISTS(A##_##M) && !IS_PROBE_PIN(A,M) && !IS_X2_ENDSTOP(A,M) && !IS_Y2_ENDSTOP(A,M) && !IS_Z2_ENDSTOP(A,M) && !IS_Z3_ENDSTOP(A,M) && !IS_Z4_ENDSTOP(A,M))
 #define HAS_X_MIN _HAS_STOP(X,MIN)
 #define HAS_X_MAX _HAS_STOP(X,MAX)
 #define HAS_Y_MIN _HAS_STOP(Y,MIN)
@@ -1027,6 +1080,8 @@
 #define HAS_Z2_MAX (PIN_EXISTS(Z2_MAX))
 #define HAS_Z3_MIN (PIN_EXISTS(Z3_MIN))
 #define HAS_Z3_MAX (PIN_EXISTS(Z3_MAX))
+#define HAS_Z4_MIN (PIN_EXISTS(Z4_MIN))
+#define HAS_Z4_MAX (PIN_EXISTS(Z4_MAX))
 #define HAS_Z_MIN_PROBE_PIN (HAS_CUSTOM_PROBE_PIN && PIN_EXISTS(Z_MIN_PROBE))
 #define HAS_CALIBRATION_PIN (PIN_EXISTS(CALIBRATION))
 
@@ -1147,7 +1202,7 @@
 #define HAS_DIGIPOTSS         (PIN_EXISTS(DIGIPOTSS))
 #define HAS_MOTOR_CURRENT_PWM ANY_PIN(MOTOR_CURRENT_PWM_X, MOTOR_CURRENT_PWM_Y, MOTOR_CURRENT_PWM_XY, MOTOR_CURRENT_PWM_Z, MOTOR_CURRENT_PWM_E)
 
-#define HAS_SOME_Z_MICROSTEPS (HAS_Z_MICROSTEPS || HAS_Z2_MICROSTEPS || HAS_Z3_MICROSTEPS)
+#define HAS_SOME_Z_MICROSTEPS (HAS_Z_MICROSTEPS || HAS_Z2_MICROSTEPS || HAS_Z3_MICROSTEPS || HAS_Z4_MICROSTEPS)
 #define HAS_SOME_E_MICROSTEPS (HAS_E0_MICROSTEPS || HAS_E1_MICROSTEPS || HAS_E2_MICROSTEPS || HAS_E3_MICROSTEPS || HAS_E4_MICROSTEPS || HAS_E5_MICROSTEPS)
 #define HAS_MICROSTEPS (HAS_X_MICROSTEPS || HAS_X2_MICROSTEPS || HAS_Y_MICROSTEPS || HAS_Y2_MICROSTEPS || HAS_SOME_Z_MICROSTEPS || HAS_SOME_E_MICROSTEPS)
 
@@ -1753,14 +1808,6 @@
 // If platform requires early initialization of watchdog to properly boot
 #define EARLY_WATCHDOG (ENABLED(USE_WATCHDOG) && defined(ARDUINO_ARCH_SAM))
 
-#if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
-  #define Z_STEPPER_COUNT 3
-#elif ENABLED(Z_DUAL_STEPPER_DRIVERS)
-  #define Z_STEPPER_COUNT 2
-#else
-  #define Z_STEPPER_COUNT 1
-#endif
-
 #if HAS_SPI_LCD
   // Get LCD character width/height, which may be overridden by pins, configs, etc.
   #ifndef LCD_WIDTH

Marlin/src/inc/SanityCheck.h

@@ -426,6 +426,28 @@
   #error "HOME_USING_SPREADCYCLE is now obsolete. Please remove it from Configuration_adv.h."
 #elif defined(DGUS_LCD)
   #error "DGUS_LCD is now DGUS_LCD_UI_(ORIGIN|FYSETC|HIPRECY). Please update your configuration."
+#elif defined(X_DUAL_ENDSTOPS_ADJUSTMENT)
+  #error "X_DUAL_ENDSTOPS_ADJUSTMENT is now X2_ENDSTOP_ADJUSTMENT. Please update Configuration_adv.h."
+#elif defined(Y_DUAL_ENDSTOPS_ADJUSTMENT)
+  #error "Y_DUAL_ENDSTOPS_ADJUSTMENT is now Y2_ENDSTOP_ADJUSTMENT. Please update Configuration_adv.h."
+#elif defined(Z_DUAL_ENDSTOPS_ADJUSTMENT)
+  #error "Z_DUAL_ENDSTOPS_ADJUSTMENT is now Z2_ENDSTOP_ADJUSTMENT. Please update Configuration_adv.h."
+#elif defined(Z_TRIPLE_ENDSTOPS_ADJUSTMENT2) || defined(Z_TRIPLE_ENDSTOPS_ADJUSTMENT3)
+  #error "Z_TRIPLE_ENDSTOPS_ADJUSTMENT[23] is now Z[23]_ENDSTOP_ADJUSTMENT. Please update Configuration_adv.h."
+#elif defined(Z_QUAD_ENDSTOPS_ADJUSTMENT2) || defined(Z_QUAD_ENDSTOPS_ADJUSTMENT3) || defined(Z_QUAD_ENDSTOPS_ADJUSTMENT4)
+  #error "Z_QUAD_ENDSTOPS_ADJUSTMENT[234] is now Z[234]_ENDSTOP_ADJUSTMENT. Please update Configuration_adv.h."
+#elif defined(Z_DUAL_STEPPER_DRIVERS)
+  #error "Z_DUAL_STEPPER_DRIVERS is now NUM_Z_STEPPER_DRIVERS with a value of 2. Please update Configuration_adv.h."
+#elif defined(Z_TRIPLE_STEPPER_DRIVERS)
+  #error "Z_TRIPLE_STEPPER_DRIVERS is now NUM_Z_STEPPER_DRIVERS with a value of 3. Please update Configuration_adv.h."
+#elif defined(Z_QUAD_STEPPER_DRIVERS)
+  #error "Z_QUAD_STEPPER_DRIVERS is now NUM_Z_STEPPER_DRIVERS with a value of 4. Please update Configuration_adv.h."
+#elif defined(Z_DUAL_ENDSTOPS)
+  #error "Z_DUAL_ENDSTOPS is now Z_MULTI_ENDSTOPS. Please update Configuration_adv.h."
+#elif defined(Z_TRIPLE_ENDSTOPS)
+  #error "Z_TRIPLE_ENDSTOPS is now Z_MULTI_ENDSTOPS. Please update Configuration_adv.h."
+#elif defined(Z_QUAD_ENDSTOPS)
+  #error "Z_QUAD_ENDSTOPS is now Z_MULTI_ENDSTOPS. Please update Configuration_adv.h."
 #endif
 
 /**
@@ -473,22 +495,27 @@
 #endif
 
 /**
- * Dual / Triple Stepper Drivers
+ * Multiple Stepper Drivers Per Axis
  */
-#if BOTH(X_DUAL_STEPPER_DRIVERS, DUAL_X_CARRIAGE)
+#define GOOD_AXIS_PINS(A) (HAS_##A##_ENABLE && HAS_##A##_STEP && HAS_##A##_DIR)
+#if ENABLED(X_DUAL_STEPPER_DRIVERS)
+  #if ENABLED(DUAL_X_CARRIAGE)
     #error "DUAL_X_CARRIAGE is not compatible with X_DUAL_STEPPER_DRIVERS."
-#elif ENABLED(X_DUAL_STEPPER_DRIVERS) && !(HAS_X2_ENABLE && HAS_X2_STEP && HAS_X2_DIR)
+  #elif !GOOD_AXIS_PINS(X)
-  #error "X_DUAL_STEPPER_DRIVERS requires X2 pins (and an extra E plug)."
+    #error "X_DUAL_STEPPER_DRIVERS requires X2 pins to be defined."
-#elif ENABLED(Y_DUAL_STEPPER_DRIVERS) && !(HAS_Y2_ENABLE && HAS_Y2_STEP && HAS_Y2_DIR)
-  #error "Y_DUAL_STEPPER_DRIVERS requires Y2 pins (and an extra E plug)."
-#elif ENABLED(Z_DUAL_STEPPER_DRIVERS)
-  #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
-    #error "Please select either Z_TRIPLE_STEPPER_DRIVERS or Z_DUAL_STEPPER_DRIVERS, not both."
-  #elif !(HAS_Z2_ENABLE && HAS_Z2_STEP && HAS_Z2_DIR)
-    #error "Z_DUAL_STEPPER_DRIVERS requires Z2 pins (and an extra E plug)."
   #endif
-#elif ENABLED(Z_TRIPLE_STEPPER_DRIVERS) && !(HAS_Z2_ENABLE && HAS_Z2_STEP && HAS_Z2_DIR && HAS_Z3_ENABLE && HAS_Z3_STEP && HAS_Z3_DIR)
+#endif
-  #error "Z_TRIPLE_STEPPER_DRIVERS requires Z3 pins (and two extra E plugs)."
+
+#if ENABLED(Y_DUAL_STEPPER_DRIVERS) && !GOOD_AXIS_PINS(Y)
+  #error "Y_DUAL_STEPPER_DRIVERS requires Y2 pins to be defined."
+#elif !WITHIN(NUM_Z_STEPPER_DRIVERS, 1, 4)
+  #error "NUM_Z_STEPPER_DRIVERS must be an integer from 1 to 4."
+#elif NUM_Z_STEPPER_DRIVERS == 2 && !GOOD_AXIS_PINS(Z2)
+  #error "If NUM_Z_STEPPER_DRIVERS is 2, you must define stepper pins for Z2."
+#elif NUM_Z_STEPPER_DRIVERS == 3 && !(GOOD_AXIS_PINS(Z2) && GOOD_AXIS_PINS(Z3))
+  #error "If NUM_Z_STEPPER_DRIVERS is 3, you must define stepper pins for Z2 and Z3."
+#elif NUM_Z_STEPPER_DRIVERS == 4 && !(GOOD_AXIS_PINS(Z2) && GOOD_AXIS_PINS(Z3) && GOOD_AXIS_PINS(Z4))
+  #error "If NUM_Z_STEPPER_DRIVERS is 4, you must define stepper pins for Z2, Z3, and Z4."
 #endif
 
 /**
@@ -1393,7 +1420,7 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
     #error "DUAL_X_CARRIAGE requires 2 (or more) extruders."
   #elif CORE_IS_XY || CORE_IS_XZ
     #error "DUAL_X_CARRIAGE cannot be used with COREXY, COREYX, COREXZ, or COREZX."
-  #elif !(HAS_X2_ENABLE && HAS_X2_STEP && HAS_X2_DIR)
+  #elif !GOOD_AXIS_PINS(X2)
     #error "DUAL_X_CARRIAGE requires X2 stepper pins to be defined."
   #elif !HAS_X_MAX
     #error "DUAL_X_CARRIAGE requires USE_XMAX_PLUG and an X Max Endstop."
@@ -1404,6 +1431,8 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
   #endif
 #endif
 
+#undef GOOD_AXIS_PINS
+
 /**
  * Make sure auto fan pins don't conflict with the fan pin
  */
@@ -1695,7 +1724,7 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
   #error "Enable USE_ZMAX_PLUG when homing Z to MAX."
 #endif
 
-// Dual endstops requirements
+// Dual/multiple endstops requirements
 #if ENABLED(X_DUAL_ENDSTOPS)
   #if !X2_USE_ENDSTOP
     #error "You must set X2_USE_ENDSTOP with X_DUAL_ENDSTOPS."
@@ -1738,9 +1767,10 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
     #error "Y_DUAL_ENDSTOPS is not compatible with DELTA."
   #endif
 #endif
-#if ENABLED(Z_DUAL_ENDSTOPS)
+
+#if ENABLED(Z_MULTI_ENDSTOPS)
   #if !Z2_USE_ENDSTOP
-    #error "You must set Z2_USE_ENDSTOP with Z_DUAL_ENDSTOPS."
+    #error "You must set Z2_USE_ENDSTOP with Z_MULTI_ENDSTOPS when NUM_Z_STEPPER_DRIVERS >= 2."
   #elif Z2_USE_ENDSTOP == _XMIN_ && DISABLED(USE_XMIN_PLUG)
     #error "USE_XMIN_PLUG is required when Z2_USE_ENDSTOP is _XMIN_."
   #elif Z2_USE_ENDSTOP == _XMAX_ && DISABLED(USE_XMAX_PLUG)
@@ -1756,31 +1786,11 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
   #elif !HAS_Z2_MIN && !HAS_Z2_MAX
     #error "Z2_USE_ENDSTOP has been assigned to a nonexistent endstop!"
   #elif ENABLED(DELTA)
-    #error "Z_DUAL_ENDSTOPS is not compatible with DELTA."
+    #error "Z_MULTI_ENDSTOPS is not compatible with DELTA."
-  #endif
-#endif
-#if ENABLED(Z_TRIPLE_ENDSTOPS)
-  #if !Z2_USE_ENDSTOP
-    #error "You must set Z2_USE_ENDSTOP with Z_TRIPLE_ENDSTOPS."
-  #elif Z2_USE_ENDSTOP == _XMIN_ && DISABLED(USE_XMIN_PLUG)
-    #error "USE_XMIN_PLUG is required when Z2_USE_ENDSTOP is _XMIN_."
-  #elif Z2_USE_ENDSTOP == _XMAX_ && DISABLED(USE_XMAX_PLUG)
-    #error "USE_XMAX_PLUG is required when Z2_USE_ENDSTOP is _XMAX_."
-  #elif Z2_USE_ENDSTOP == _YMIN_ && DISABLED(USE_YMIN_PLUG)
-    #error "USE_YMIN_PLUG is required when Z2_USE_ENDSTOP is _YMIN_."
-  #elif Z2_USE_ENDSTOP == _YMAX_ && DISABLED(USE_YMAX_PLUG)
-    #error "USE_YMAX_PLUG is required when Z2_USE_ENDSTOP is _YMAX_."
-  #elif Z2_USE_ENDSTOP == _ZMIN_ && DISABLED(USE_ZMIN_PLUG)
-    #error "USE_ZMIN_PLUG is required when Z2_USE_ENDSTOP is _ZMIN_."
-  #elif Z2_USE_ENDSTOP == _ZMAX_ && DISABLED(USE_ZMAX_PLUG)
-    #error "USE_ZMAX_PLUG is required when Z2_USE_ENDSTOP is _ZMAX_."
-  #elif !HAS_Z2_MIN && !HAS_Z2_MAX
-    #error "Z2_USE_ENDSTOP has been assigned to a nonexistent endstop!"
-  #elif ENABLED(DELTA)
-    #error "Z_TRIPLE_ENDSTOPS is not compatible with DELTA."
   #endif
+  #if NUM_Z_STEPPER_DRIVERS >= 3
     #if !Z3_USE_ENDSTOP
-    #error "You must set Z3_USE_ENDSTOP with Z_TRIPLE_ENDSTOPS."
+      #error "You must set Z3_USE_ENDSTOP with Z_MULTI_ENDSTOPS when NUM_Z_STEPPER_DRIVERS >= 3."
     #elif Z3_USE_ENDSTOP == _XMIN_ && DISABLED(USE_XMIN_PLUG)
       #error "USE_XMIN_PLUG is required when Z3_USE_ENDSTOP is _XMIN_."
     #elif Z3_USE_ENDSTOP == _XMAX_ && DISABLED(USE_XMAX_PLUG)
@@ -1795,8 +1805,26 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
       #error "USE_ZMAX_PLUG is required when Z3_USE_ENDSTOP is _ZMAX_."
     #elif !HAS_Z3_MIN && !HAS_Z3_MAX
       #error "Z3_USE_ENDSTOP has been assigned to a nonexistent endstop!"
-  #elif ENABLED(DELTA)
+    #endif
-    #error "Z_TRIPLE_ENDSTOPS is not compatible with DELTA."
+  #endif
+  #if NUM_Z_STEPPER_DRIVERS >= 4
+    #if !Z4_USE_ENDSTOP
+      #error "You must set Z4_USE_ENDSTOP with Z_MULTI_ENDSTOPS when NUM_Z_STEPPER_DRIVERS >= 4."
+    #elif Z4_USE_ENDSTOP == _XMIN_ && DISABLED(USE_XMIN_PLUG)
+      #error "USE_XMIN_PLUG is required when Z4_USE_ENDSTOP is _XMIN_."
+    #elif Z4_USE_ENDSTOP == _XMAX_ && DISABLED(USE_XMAX_PLUG)
+      #error "USE_XMAX_PLUG is required when Z4_USE_ENDSTOP is _XMAX_."
+    #elif Z4_USE_ENDSTOP == _YMIN_ && DISABLED(USE_YMIN_PLUG)
+      #error "USE_YMIN_PLUG is required when Z4_USE_ENDSTOP is _YMIN_."
+    #elif Z4_USE_ENDSTOP == _YMAX_ && DISABLED(USE_YMAX_PLUG)
+      #error "USE_YMAX_PLUG is required when Z4_USE_ENDSTOP is _YMAX_."
+    #elif Z4_USE_ENDSTOP == _ZMIN_ && DISABLED(USE_ZMIN_PLUG)
+      #error "USE_ZMIN_PLUG is required when Z4_USE_ENDSTOP is _ZMIN_."
+    #elif Z4_USE_ENDSTOP == _ZMAX_ && DISABLED(USE_ZMAX_PLUG)
+      #error "USE_ZMAX_PLUG is required when Z4_USE_ENDSTOP is _ZMAX_."
+    #elif !HAS_Z4_MIN && !HAS_Z4_MAX
+      #error "Z4_USE_ENDSTOP has been assigned to a nonexistent endstop!"
+    #endif
   #endif
 #endif
 
@@ -2321,12 +2349,12 @@ static_assert(   _ARR_TEST(3,0) && _ARR_TEST(3,1) && _ARR_TEST(3,2)
 #endif
 
 #if ENABLED(Z_STEPPER_AUTO_ALIGN)
-  #if !Z_MULTI_STEPPER_DRIVERS
+  #if NUM_Z_STEPPER_DRIVERS <= 1
-    #error "Z_STEPPER_AUTO_ALIGN requires Z_DUAL_STEPPER_DRIVERS or Z_TRIPLE_STEPPER_DRIVERS."
+    #error "Z_STEPPER_AUTO_ALIGN requires NUM_Z_STEPPER_DRIVERS greater than 1."
   #elif !HAS_BED_PROBE
     #error "Z_STEPPER_AUTO_ALIGN requires a Z-bed probe."
-  #elif ENABLED(Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS) && DISABLED(Z_TRIPLE_STEPPER_DRIVERS)
+  #elif ENABLED(Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS) && NUM_Z_STEPPER_DRIVERS != 3
-    #error "Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS requires Z_TRIPLE_STEPPER_DRIVERS."
+    #error "Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS requires NUM_Z_STEPPER_DRIVERS to be 3."
   #endif
 #endif
 

Marlin/src/lcd/menu/menu_tmc.cpp

@@ -58,6 +58,9 @@ void menu_tmc_current() {
   #if AXIS_IS_TMC(Z3)
     TMC_EDIT_STORED_I_RMS(Z3, MSG_Z3);
   #endif
+  #if AXIS_IS_TMC(Z4)
+    TMC_EDIT_STORED_I_RMS(Z4, MSG_Z4);
+  #endif
   #if AXIS_IS_TMC(E0)
     TMC_EDIT_STORED_I_RMS(E0, LCD_STR_E0);
   #endif
@@ -107,6 +110,9 @@ void menu_tmc_current() {
     #if AXIS_HAS_STEALTHCHOP(Z3)
       TMC_EDIT_STORED_HYBRID_THRS(Z3, MSG_Z3);
     #endif
+    #if AXIS_HAS_STEALTHCHOP(Z4)
+      TMC_EDIT_STORED_HYBRID_THRS(Z4, MSG_Z4);
+    #endif
     #if AXIS_HAS_STEALTHCHOP(E0)
       TMC_EDIT_STORED_HYBRID_THRS(E0, LCD_STR_E0);
     #endif
@@ -183,6 +189,9 @@ void menu_tmc_current() {
     #if AXIS_HAS_STEALTHCHOP(Z3)
       TMC_EDIT_STEP_MODE(Z3, MSG_Z3);
     #endif
+    #if AXIS_HAS_STEALTHCHOP(Z4)
+      TMC_EDIT_STEP_MODE(Z4, MSG_Z4);
+    #endif
     #if AXIS_HAS_STEALTHCHOP(E0)
       TMC_EDIT_STEP_MODE(E0, LCD_STR_E0);
     #endif

Marlin/src/libs/L64XX/L64XX_Marlin.cpp

@@ -39,7 +39,7 @@ L64XX_Marlin L64xxManager;
 
 void echo_yes_no(const bool yes) { serialprintPGM(yes ? PSTR(" YES") : PSTR(" NO ")); }
 
-char L64XX_Marlin::index_to_axis[MAX_L64XX][3] = { "X ", "Y ", "Z ", "X2", "Y2", "Z2", "Z3", "E0", "E1", "E2", "E3", "E4", "E5" };
+char L64XX_Marlin::index_to_axis[MAX_L64XX][3] = { "X ", "Y ", "Z ", "X2", "Y2", "Z2", "Z3", "Z4", "E0", "E1", "E2", "E3", "E4", "E5" };
 
 #define DEBUG_OUT ENABLED(L6470_CHITCHAT)
 #include "../../core/debug_out.h"
@@ -61,12 +61,14 @@ uint8_t L64XX_Marlin::index_to_dir[MAX_L64XX] = { (INVERT_X_DIR),
                                                   #endif
                                                   (INVERT_Z_DIR),                         //  5 Z2
                                                   (INVERT_Z_DIR),                         //  6 Z3
-                                                  (INVERT_E0_DIR),                        //  7 E0
+                                                  (INVERT_Z_DIR),                         //  7 Z4
-                                                  (INVERT_E1_DIR),                        //  8 E1
+
-                                                  (INVERT_E2_DIR),                        //  9 E2
+                                                  (INVERT_E0_DIR),                        //  8 E0
-                                                  (INVERT_E3_DIR),                        // 10 E3
+                                                  (INVERT_E1_DIR),                        //  9 E1
-                                                  (INVERT_E4_DIR),                        // 11 E4
+                                                  (INVERT_E2_DIR),                        // 10 E2
-                                                  (INVERT_E5_DIR),                        // 12 E5
+                                                  (INVERT_E3_DIR),                        // 11 E3
+                                                  (INVERT_E4_DIR),                        // 12 E4
+                                                  (INVERT_E5_DIR),                        // 13 E5
                                                 };
 
 volatile uint8_t L64XX_Marlin::spi_abort = false;
@@ -101,6 +103,9 @@ void L6470_populate_chain_array() {
   #if AXIS_IS_L64XX(Z3)
     _L6470_INIT_SPI(Z3);
   #endif
+  #if AXIS_IS_L64XX(Z4)
+    _L6470_INIT_SPI(Z4);
+  #endif
   #if AXIS_IS_L64XX(E0)
     _L6470_INIT_SPI(E0);
   #endif
@@ -211,6 +216,9 @@ uint16_t L64XX_Marlin::get_status(const L64XX_axis_t axis) {
     #if AXIS_IS_L64XX(Z3)
       case Z3: return STATUS_L6470(Z3);
     #endif
+    #if AXIS_IS_L64XX(Z4)
+      case Z4: return STATUS_L6470(Z4);
+    #endif
     #if AXIS_IS_L64XX(E0)
       case E0: return STATUS_L6470(E0);
     #endif
@@ -261,6 +269,9 @@ uint32_t L64XX_Marlin::get_param(const L64XX_axis_t axis, const uint8_t param) {
     #if AXIS_IS_L64XX(Z3)
       case Z3: return GET_L6470_PARAM(Z3);
     #endif
+    #if AXIS_IS_L64XX(Z4)
+      case Z4: return GET_L6470_PARAM(Z4);
+    #endif
     #if AXIS_IS_L64XX(E0)
       case E0: return GET_L6470_PARAM(E0);
     #endif
@@ -311,6 +322,9 @@ void L64XX_Marlin::set_param(const L64XX_axis_t axis, const uint8_t param, const
     #if AXIS_IS_L64XX(Z3)
       case Z3: SET_L6470_PARAM(Z3); break;
     #endif
+    #if AXIS_IS_L64XX(Z4)
+      case Z4: SET_L6470_PARAM(Z4); break;
+    #endif
     #if AXIS_IS_L64XX(E0)
       case E0: SET_L6470_PARAM(E0); break;
     #endif
@@ -684,6 +698,9 @@ void L64XX_Marlin::say_axis(const L64XX_axis_t axis, const uint8_t label/*=true*
     #if AXIS_IS_L64XX(Z3)
       {  6, 0, 0, 0, 0, 0, 0 },
     #endif
+    #if AXIS_IS_L64XX(Z4)
+      {  6, 0, 0, 0, 0, 0, 0 },
+    #endif
     #if AXIS_IS_L64XX(E0)
       {  7, 0, 0, 0, 0, 0, 0 },
     #endif
@@ -858,6 +875,9 @@ void L64XX_Marlin::say_axis(const L64XX_axis_t axis, const uint8_t label/*=true*
         #if AXIS_IS_L64XX(Z3)
           monitor_update(Z3);
         #endif
+        #if AXIS_IS_L64XX(Z4)
+          monitor_update(Z4);
+        #endif
         #if AXIS_IS_L64XX(E0)
           monitor_update(E0);
         #endif

Marlin/src/libs/L64XX/L64XX_Marlin.h

@@ -35,7 +35,7 @@
 #define dSPIN_STEP_CLOCK_REV dSPIN_STEP_CLOCK+1
 #define HAS_L64XX_EXTRUDER (AXIS_IS_L64XX(E0) || AXIS_IS_L64XX(E1) || AXIS_IS_L64XX(E2) || AXIS_IS_L64XX(E3) || AXIS_IS_L64XX(E4) || AXIS_IS_L64XX(E5))
 
-enum L64XX_axis_t : uint8_t { X, Y, Z, X2, Y2, Z2, Z3, E0, E1, E2, E3, E4, E5, MAX_L64XX };
+enum L64XX_axis_t : uint8_t { X, Y, Z, X2, Y2, Z2, Z3, Z4, E0, E1, E2, E3, E4, E5, MAX_L64XX };
 
 class L64XX_Marlin : public L64XXHelper {
 public:

Marlin/src/module/configuration_store.cpp

@@ -37,7 +37,7 @@
  */
 
 // Change EEPROM version if the structure changes
-#define EEPROM_VERSION "V74"
+#define EEPROM_VERSION "V75"
 #define EEPROM_OFFSET 100
 
 // Check the integrity of data offsets.
@@ -120,10 +120,10 @@
 
 #pragma pack(push, 1) // No padding between variables
 
-typedef struct { uint16_t X, Y, Z, X2, Y2, Z2, Z3, E0, E1, E2, E3, E4, E5; } tmc_stepper_current_t;
+typedef struct { uint16_t X, Y, Z, X2, Y2, Z2, Z3, Z4, E0, E1, E2, E3, E4, E5; } tmc_stepper_current_t;
-typedef struct { uint32_t X, Y, Z, X2, Y2, Z2, Z3, E0, E1, E2, E3, E4, E5; } tmc_hybrid_threshold_t;
+typedef struct { uint32_t X, Y, Z, X2, Y2, Z2, Z3, Z4, E0, E1, E2, E3, E4, E5; } tmc_hybrid_threshold_t;
 typedef struct {  int16_t X, Y, Z, X2;                                     } tmc_sgt_t;
-typedef struct {     bool X, Y, Z, X2, Y2, Z2, Z3, E0, E1, E2, E3, E4, E5; } tmc_stealth_enabled_t;
+typedef struct {     bool X, Y, Z, X2, Y2, Z2, Z3, Z4, E0, E1, E2, E3, E4, E5; } tmc_stealth_enabled_t;
 
 // Limit an index to an array size
 #define ALIM(I,ARR) _MIN(I, COUNT(ARR) - 1)
@@ -243,11 +243,12 @@ typedef struct SettingsDataStruct {
           delta_diagonal_rod,                           // M665 L
           delta_segments_per_second;                    // M665 S
     abc_float_t delta_tower_angle_trim;                 // M665 XYZ
-  #elif EITHER(X_DUAL_ENDSTOPS, Y_DUAL_ENDSTOPS) || Z_MULTI_ENDSTOPS
+  #elif HAS_EXTRA_ENDSTOPS
     float x2_endstop_adj,                               // M666 X
           y2_endstop_adj,                               // M666 Y
-          z2_endstop_adj,                               // M666 Z (S2)
+          z2_endstop_adj,                               // M666 (S2) Z
-          z3_endstop_adj;                               // M666 Z (S3)
+          z3_endstop_adj,                               // M666 (S3) Z
+          z4_endstop_adj;                               // M666 (S4) Z
   #endif
 
   //
@@ -300,10 +301,10 @@ typedef struct SettingsDataStruct {
   //
   // HAS_TRINAMIC
   //
-  tmc_stepper_current_t tmc_stepper_current;            // M906 X Y Z X2 Y2 Z2 Z3 E0 E1 E2 E3 E4 E5
+  tmc_stepper_current_t tmc_stepper_current;            // M906 X Y Z X2 Y2 Z2 Z3 Z4 E0 E1 E2 E3 E4 E5
-  tmc_hybrid_threshold_t tmc_hybrid_threshold;          // M913 X Y Z X2 Y2 Z2 Z3 E0 E1 E2 E3 E4 E5
+  tmc_hybrid_threshold_t tmc_hybrid_threshold;          // M913 X Y Z X2 Y2 Z2 Z3 Z4 E0 E1 E2 E3 E4 E5
   tmc_sgt_t tmc_sgt;                                    // M914 X Y Z X2
-  tmc_stealth_enabled_t tmc_stealth_enabled;            // M569 X Y Z X2 Y2 Z2 Z3 E0 E1 E2 E3 E4 E5
+  tmc_stealth_enabled_t tmc_stealth_enabled;            // M569 X Y Z X2 Y2 Z2 Z3 Z4 E0 E1 E2 E3 E4 E5
 
   //
   // LIN_ADVANCE
@@ -756,7 +757,7 @@ void MarlinSettings::postprocess() {
         EEPROM_WRITE(delta_segments_per_second); // 1 float
         EEPROM_WRITE(delta_tower_angle_trim);    // 3 floats
 
-      #elif EITHER(X_DUAL_ENDSTOPS, Y_DUAL_ENDSTOPS) || Z_MULTI_ENDSTOPS
+      #elif HAS_EXTRA_ENDSTOPS
 
         _FIELD_TEST(x2_endstop_adj);
 
@@ -774,18 +775,24 @@ void MarlinSettings::postprocess() {
           EEPROM_WRITE(dummy);
         #endif
 
-        #if Z_MULTI_ENDSTOPS
+        #if ENABLED(Z_MULTI_ENDSTOPS)
           EEPROM_WRITE(endstops.z2_endstop_adj);   // 1 float
         #else
           EEPROM_WRITE(dummy);
         #endif
 
-        #if ENABLED(Z_TRIPLE_ENDSTOPS)
+        #if ENABLED(Z_MULTI_ENDSTOPS) && NUM_Z_STEPPER_DRIVERS >= 3
           EEPROM_WRITE(endstops.z3_endstop_adj);   // 1 float
         #else
           EEPROM_WRITE(dummy);
         #endif
 
+        #if ENABLED(Z_MULTI_ENDSTOPS) && NUM_Z_STEPPER_DRIVERS >= 4
+          EEPROM_WRITE(endstops.z4_endstop_adj);   // 1 float
+        #else
+          EEPROM_WRITE(dummy);
+        #endif
+
       #endif
     }
 
@@ -974,6 +981,9 @@ void MarlinSettings::postprocess() {
         #if AXIS_IS_TMC(Z3)
           tmc_stepper_current.Z3 = stepperZ3.getMilliamps();
         #endif
+        #if AXIS_IS_TMC(Z4)
+          tmc_stepper_current.Z4 = stepperZ4.getMilliamps();
+        #endif
         #if MAX_EXTRUDERS
           #if AXIS_IS_TMC(E0)
             tmc_stepper_current.E0 = stepperE0.getMilliamps();
@@ -1037,6 +1047,9 @@ void MarlinSettings::postprocess() {
         #if AXIS_HAS_STEALTHCHOP(Z3)
           tmc_hybrid_threshold.Z3 = stepperZ3.get_pwm_thrs();
         #endif
+        #if AXIS_HAS_STEALTHCHOP(Z4)
+          tmc_hybrid_threshold.Z4 = stepperZ4.get_pwm_thrs();
+        #endif
         #if MAX_EXTRUDERS
           #if AXIS_HAS_STEALTHCHOP(E0)
             tmc_hybrid_threshold.E0 = stepperE0.get_pwm_thrs();
@@ -1070,7 +1083,7 @@ void MarlinSettings::postprocess() {
       #else
         const tmc_hybrid_threshold_t tmc_hybrid_threshold = {
           .X  = 100, .Y  = 100, .Z  =   3,
-          .X2 = 100, .Y2 = 100, .Z2 =   3, .Z3 =   3,
+          .X2 = 100, .Y2 = 100, .Z2 =   3, .Z3 =   3, .Z4 = 3,
           .E0 =  30, .E1 =  30, .E2 =  30,
           .E3 =  30, .E4 =  30, .E5 =  30
         };
@@ -1130,6 +1143,9 @@ void MarlinSettings::postprocess() {
         #if AXIS_HAS_STEALTHCHOP(Z3)
           tmc_stealth_enabled.Z3 = stepperZ3.get_stealthChop_status();
         #endif
+        #if AXIS_HAS_STEALTHCHOP(Z4)
+          tmc_stealth_enabled.Z4 = stepperZ4.get_stealthChop_status();
+        #endif
         #if MAX_EXTRUDERS
           #if AXIS_HAS_STEALTHCHOP(E0)
             tmc_stealth_enabled.E0 = stepperE0.get_stealthChop_status();
@@ -1585,7 +1601,7 @@ void MarlinSettings::postprocess() {
           EEPROM_READ(delta_segments_per_second); // 1 float
           EEPROM_READ(delta_tower_angle_trim);    // 3 floats
 
-        #elif EITHER(X_DUAL_ENDSTOPS, Y_DUAL_ENDSTOPS) || Z_MULTI_ENDSTOPS
+        #elif HAS_EXTRA_ENDSTOPS
 
           _FIELD_TEST(x2_endstop_adj);
 
@@ -1599,16 +1615,21 @@ void MarlinSettings::postprocess() {
           #else
             EEPROM_READ(dummy);
           #endif
-          #if Z_MULTI_ENDSTOPS
+          #if ENABLED(Z_MULTI_ENDSTOPS)
             EEPROM_READ(endstops.z2_endstop_adj); // 1 float
           #else
             EEPROM_READ(dummy);
           #endif
-          #if ENABLED(Z_TRIPLE_ENDSTOPS)
+          #if ENABLED(Z_MULTI_ENDSTOPS) && NUM_Z_STEPPER_DRIVERS >= 3
             EEPROM_READ(endstops.z3_endstop_adj); // 1 float
           #else
             EEPROM_READ(dummy);
           #endif
+          #if ENABLED(Z_MULTI_ENDSTOPS) && NUM_Z_STEPPER_DRIVERS >= 4
+            EEPROM_READ(endstops.z4_endstop_adj); // 1 float
+          #else
+            EEPROM_READ(dummy);
+          #endif
 
         #endif
       }
@@ -1800,6 +1821,9 @@ void MarlinSettings::postprocess() {
             #if AXIS_IS_TMC(Z3)
               SET_CURR(Z3);
             #endif
+            #if AXIS_IS_TMC(Z4)
+              SET_CURR(Z4);
+            #endif
             #if AXIS_IS_TMC(E0)
               SET_CURR(E0);
             #endif
@@ -1851,6 +1875,9 @@ void MarlinSettings::postprocess() {
             #if AXIS_HAS_STEALTHCHOP(Z3)
               stepperZ3.set_pwm_thrs(tmc_hybrid_threshold.Z3);
             #endif
+            #if AXIS_HAS_STEALTHCHOP(Z4)
+              stepperZ4.set_pwm_thrs(tmc_hybrid_threshold.Z4);
+            #endif
             #if AXIS_HAS_STEALTHCHOP(E0)
               stepperE0.set_pwm_thrs(tmc_hybrid_threshold.E0);
             #endif
@@ -1877,7 +1904,7 @@ void MarlinSettings::postprocess() {
       // TMC StallGuard threshold.
       // X and X2 use the same value
       // Y and Y2 use the same value
-      // Z, Z2 and Z3 use the same value
+      // Z, Z2, Z3 and Z4 use the same value
       //
       {
         tmc_sgt_t tmc_sgt;
@@ -1914,6 +1941,9 @@ void MarlinSettings::postprocess() {
               #if AXIS_HAS_STALLGUARD(Z3)
                 stepperZ3.homing_threshold(tmc_sgt.Z);
               #endif
+              #if AXIS_HAS_STALLGUARD(Z4)
+                stepperZ4.homing_threshold(tmc_sgt.Z);
+              #endif
             #endif
           }
         #endif
@@ -1951,6 +1981,9 @@ void MarlinSettings::postprocess() {
             #if AXIS_HAS_STEALTHCHOP(Z3)
               SET_STEPPING_MODE(Z3);
             #endif
+            #if AXIS_HAS_STEALTHCHOP(Z4)
+              SET_STEPPING_MODE(Z4);
+            #endif
             #if AXIS_HAS_STEALTHCHOP(E0)
               SET_STEPPING_MODE(E0);
             #endif
@@ -2433,51 +2466,39 @@ void MarlinSettings::reset() {
     delta_segments_per_second = DELTA_SEGMENTS_PER_SECOND;
     delta_tower_angle_trim = dta;
 
-  #elif EITHER(X_DUAL_ENDSTOPS, Y_DUAL_ENDSTOPS) || Z_MULTI_ENDSTOPS
+  #endif
 
   #if ENABLED(X_DUAL_ENDSTOPS)
-      endstops.x2_endstop_adj = (
+    #ifndef X2_ENDSTOP_ADJUSTMENT
-        #ifdef X_DUAL_ENDSTOPS_ADJUSTMENT
+      #define X2_ENDSTOP_ADJUSTMENT 0
-          X_DUAL_ENDSTOPS_ADJUSTMENT
-        #else
-          0
     #endif
-      );
+    endstops.x2_endstop_adj = X2_ENDSTOP_ADJUSTMENT;
-    #endif
-    #if ENABLED(Y_DUAL_ENDSTOPS)
-      endstops.y2_endstop_adj = (
-        #ifdef Y_DUAL_ENDSTOPS_ADJUSTMENT
-          Y_DUAL_ENDSTOPS_ADJUSTMENT
-        #else
-          0
-        #endif
-      );
-    #endif
-    #if ENABLED(Z_DUAL_ENDSTOPS)
-      endstops.z2_endstop_adj = (
-        #ifdef Z_DUAL_ENDSTOPS_ADJUSTMENT
-          Z_DUAL_ENDSTOPS_ADJUSTMENT
-        #else
-          0
-        #endif
-      );
-    #elif ENABLED(Z_TRIPLE_ENDSTOPS)
-      endstops.z2_endstop_adj = (
-        #ifdef Z_TRIPLE_ENDSTOPS_ADJUSTMENT2
-          Z_TRIPLE_ENDSTOPS_ADJUSTMENT2
-        #else
-          0
-        #endif
-      );
-      endstops.z3_endstop_adj = (
-        #ifdef Z_TRIPLE_ENDSTOPS_ADJUSTMENT3
-          Z_TRIPLE_ENDSTOPS_ADJUSTMENT3
-        #else
-          0
-        #endif
-      );
   #endif
 
+  #if ENABLED(Y_DUAL_ENDSTOPS)
+    #ifndef Y2_ENDSTOP_ADJUSTMENT
+      #define Y2_ENDSTOP_ADJUSTMENT 0
+    #endif
+    endstops.y2_endstop_adj = Y2_ENDSTOP_ADJUSTMENT;
+  #endif
+
+  #if ENABLED(Z_MULTI_ENDSTOPS)
+    #ifndef Z2_ENDSTOP_ADJUSTMENT
+      #define Z2_ENDSTOP_ADJUSTMENT 0
+    #endif
+    endstops.z2_endstop_adj = Z2_ENDSTOP_ADJUSTMENT;
+    #if NUM_Z_STEPPER_DRIVERS >= 3
+      #ifndef Z3_ENDSTOP_ADJUSTMENT
+        #define Z3_ENDSTOP_ADJUSTMENT 0
+      #endif
+      endstops.z3_endstop_adj = Z3_ENDSTOP_ADJUSTMENT;
+    #endif
+    #if NUM_Z_STEPPER_DRIVERS >= 4
+      #ifndef Z4_ENDSTOP_ADJUSTMENT
+        #define Z4_ENDSTOP_ADJUSTMENT 0
+      #endif
+      endstops.z4_endstop_adj = Z4_ENDSTOP_ADJUSTMENT;
+    #endif
   #endif
 
   //
@@ -3016,25 +3037,30 @@ void MarlinSettings::reset() {
         , SP_Z_STR, LINEAR_UNIT(delta_tower_angle_trim.c)
       );
 
-    #elif EITHER(X_DUAL_ENDSTOPS, Y_DUAL_ENDSTOPS) || Z_MULTI_ENDSTOPS
+    #elif HAS_EXTRA_ENDSTOPS
 
       CONFIG_ECHO_HEADING("Endstop adjustment:");
       CONFIG_ECHO_START();
       SERIAL_ECHOPGM("  M666");
       #if ENABLED(X_DUAL_ENDSTOPS)
-        SERIAL_ECHOPAIR_P(SP_X_STR, LINEAR_UNIT(endstops.x2_endstop_adj));
+        SERIAL_ECHOLNPAIR_P(SP_X_STR, LINEAR_UNIT(endstops.x2_endstop_adj));
       #endif
       #if ENABLED(Y_DUAL_ENDSTOPS)
-        SERIAL_ECHOPAIR_P(SP_Y_STR, LINEAR_UNIT(endstops.y2_endstop_adj));
+        SERIAL_ECHOLNPAIR_P(SP_Y_STR, LINEAR_UNIT(endstops.y2_endstop_adj));
       #endif
-      #if ENABLED(Z_TRIPLE_ENDSTOPS)
+      #if ENABLED(Z_MULTI_ENDSTOPS)
-        SERIAL_ECHOLNPAIR("S1 Z", LINEAR_UNIT(endstops.z2_endstop_adj));
+        #if NUM_Z_STEPPER_DRIVERS >= 3
+          SERIAL_ECHOPAIR(" S2 Z", LINEAR_UNIT(endstops.z3_endstop_adj));
           CONFIG_ECHO_START();
-        SERIAL_ECHOPAIR("  M666 S2 Z", LINEAR_UNIT(endstops.z3_endstop_adj));
+          SERIAL_ECHOPAIR("  M666 S3 Z", LINEAR_UNIT(endstops.z3_endstop_adj));
-      #elif ENABLED(Z_DUAL_ENDSTOPS)
+          #if NUM_Z_STEPPER_DRIVERS >= 4
-        SERIAL_ECHOPAIR_P(SP_Z_STR, LINEAR_UNIT(endstops.z2_endstop_adj));
+            CONFIG_ECHO_START();
+            SERIAL_ECHOPAIR("  M666 S4 Z", LINEAR_UNIT(endstops.z4_endstop_adj));
+          #endif
+        #else
+          SERIAL_ECHOLNPAIR_P(SP_Z_STR, LINEAR_UNIT(endstops.z2_endstop_adj));
+        #endif
       #endif
-      SERIAL_EOL();
 
     #endif // [XYZ]_DUAL_ENDSTOPS
 
@@ -3218,6 +3244,11 @@ void MarlinSettings::reset() {
         SERIAL_ECHOLNPAIR(" I2 Z", stepperZ3.getMilliamps());
       #endif
 
+      #if AXIS_IS_TMC(Z4)
+        say_M906(forReplay);
+        SERIAL_ECHOLNPAIR(" I3 Z", stepperZ4.getMilliamps());
+      #endif
+
       #if AXIS_IS_TMC(E0)
         say_M906(forReplay);
         SERIAL_ECHOLNPAIR(" T0 E", stepperE0.getMilliamps());
@@ -3287,6 +3318,11 @@ void MarlinSettings::reset() {
           SERIAL_ECHOLNPAIR(" I2 Z", stepperZ3.get_pwm_thrs());
         #endif
 
+        #if AXIS_HAS_STEALTHCHOP(Z4)
+          say_M913(forReplay);
+          SERIAL_ECHOLNPAIR(" I3 Z", stepperZ4.get_pwm_thrs());
+        #endif
+
         #if AXIS_HAS_STEALTHCHOP(E0)
           say_M913(forReplay);
           SERIAL_ECHOLNPAIR(" T0 E", stepperE0.get_pwm_thrs());
@@ -3356,6 +3392,12 @@ void MarlinSettings::reset() {
           SERIAL_ECHOLNPAIR(" I2 Z", stepperZ3.homing_threshold());
         #endif
 
+        #if Z4_SENSORLESS
+          CONFIG_ECHO_START();
+          say_M914();
+          SERIAL_ECHOLNPAIR(" I3 Z", stepperZ4.homing_threshold());
+        #endif
+
       #endif // USE_SENSORLESS
 
       /**
@@ -3415,6 +3457,10 @@ void MarlinSettings::reset() {
           if (stepperZ3.get_stealthChop_status()) { say_M569(forReplay, PSTR("I2 Z"), true); }
         #endif
 
+        #if AXIS_HAS_STEALTHCHOP(Z4)
+          if (stepperZ4.get_stealthChop_status()) { say_M569(forReplay, PSTR("I3 Z"), true); }
+        #endif
+
         #if AXIS_HAS_STEALTHCHOP(E0)
           if (stepperE0.get_stealthChop_status()) { say_M569(forReplay, PSTR("T0 E"), true); }
         #endif

Marlin/src/module/endstops.cpp

@@ -73,11 +73,14 @@ Endstops::esbits_t Endstops::live_state = 0;
 #if ENABLED(Y_DUAL_ENDSTOPS)
   float Endstops::y2_endstop_adj;
 #endif
-#if Z_MULTI_ENDSTOPS
+#if ENABLED(Z_MULTI_ENDSTOPS)
   float Endstops::z2_endstop_adj;
-#endif
+  #if NUM_Z_STEPPER_DRIVERS >= 3
-#if ENABLED(Z_TRIPLE_ENDSTOPS)
     float Endstops::z3_endstop_adj;
+    #if NUM_Z_STEPPER_DRIVERS >= 4
+      float Endstops::z4_endstop_adj;
+    #endif
+  #endif
 #endif
 
 #if ENABLED(SPI_ENDSTOPS)
@@ -163,6 +166,16 @@ void Endstops::init() {
     #endif
   #endif
 
+  #if HAS_Z4_MIN
+    #if ENABLED(ENDSTOPPULLUP_ZMIN)
+      SET_INPUT_PULLUP(Z4_MIN_PIN);
+    #elif ENABLED(ENDSTOPPULLDOWN_ZMIN)
+      SET_INPUT_PULLDOWN(Z4_MIN_PIN);
+    #else
+      SET_INPUT(Z4_MIN_PIN);
+    #endif
+  #endif
+
   #if HAS_X_MAX
     #if ENABLED(ENDSTOPPULLUP_XMAX)
       SET_INPUT_PULLUP(X_MAX_PIN);
@@ -233,6 +246,16 @@ void Endstops::init() {
     #endif
   #endif
 
+  #if HAS_Z4_MAX
+    #if ENABLED(ENDSTOPPULLUP_ZMAX)
+      SET_INPUT_PULLUP(Z4_MAX_PIN);
+    #elif ENABLED(ENDSTOPPULLDOWN_ZMAX)
+      SET_INPUT_PULLDOWN(Z4_MAX_PIN);
+    #else
+      SET_INPUT(Z4_MAX_PIN);
+    #endif
+  #endif
+
   #if HAS_CALIBRATION_PIN
     #if ENABLED(CALIBRATION_PIN_PULLUP)
       SET_INPUT_PULLUP(CALIBRATION_PIN);
@@ -435,6 +458,9 @@ void _O2 Endstops::report_states() {
   #if HAS_Z3_MIN
     ES_REPORT(Z3_MIN);
   #endif
+  #if HAS_Z4_MIN
+    ES_REPORT(Z4_MIN);
+  #endif
   #if HAS_Z_MAX
     ES_REPORT(Z_MAX);
   #endif
@@ -444,6 +470,9 @@ void _O2 Endstops::report_states() {
   #if HAS_Z3_MAX
     ES_REPORT(Z3_MAX);
   #endif
+  #if HAS_Z4_MAX
+    ES_REPORT(Z4_MAX);
+  #endif
   #if HAS_CUSTOM_PROBE_PIN
     print_es_state(READ(Z_MIN_PROBE_PIN) != Z_MIN_PROBE_ENDSTOP_INVERTING, PSTR(MSG_Z_PROBE));
   #endif
@@ -584,19 +613,26 @@ void Endstops::update() {
 
   #if HAS_Z_MIN && !Z_SPI_SENSORLESS
     UPDATE_ENDSTOP_BIT(Z, MIN);
-    #if Z_MULTI_ENDSTOPS
+    #if ENABLED(Z_MULTI_ENDSTOPS)
       #if HAS_Z2_MIN
         UPDATE_ENDSTOP_BIT(Z2, MIN);
       #else
         COPY_LIVE_STATE(Z_MIN, Z2_MIN);
       #endif
-      #if ENABLED(Z_TRIPLE_ENDSTOPS)
+      #if NUM_Z_STEPPER_DRIVERS >= 3
         #if HAS_Z3_MIN
           UPDATE_ENDSTOP_BIT(Z3, MIN);
         #else
           COPY_LIVE_STATE(Z_MIN, Z3_MIN);
         #endif
       #endif
+      #if NUM_Z_STEPPER_DRIVERS >= 4
+        #if HAS_Z4_MIN
+          UPDATE_ENDSTOP_BIT(Z4, MIN);
+        #else
+          COPY_LIVE_STATE(Z_MIN, Z4_MIN);
+        #endif
+      #endif
     #endif
   #endif
 
@@ -607,20 +643,27 @@ void Endstops::update() {
 
   #if HAS_Z_MAX && !Z_SPI_SENSORLESS
     // Check both Z dual endstops
-    #if Z_MULTI_ENDSTOPS
+    #if ENABLED(Z_MULTI_ENDSTOPS)
       UPDATE_ENDSTOP_BIT(Z, MAX);
       #if HAS_Z2_MAX
         UPDATE_ENDSTOP_BIT(Z2, MAX);
       #else
         COPY_LIVE_STATE(Z_MAX, Z2_MAX);
       #endif
-      #if ENABLED(Z_TRIPLE_ENDSTOPS)
+      #if NUM_Z_STEPPER_DRIVERS >= 3
         #if HAS_Z3_MAX
           UPDATE_ENDSTOP_BIT(Z3, MAX);
         #else
           COPY_LIVE_STATE(Z_MAX, Z3_MAX);
         #endif
       #endif
+      #if NUM_Z_STEPPER_DRIVERS >= 4
+        #if HAS_Z4_MAX
+          UPDATE_ENDSTOP_BIT(Z4, MAX);
+        #else
+          COPY_LIVE_STATE(Z_MAX, Z4_MAX);
+        #endif
+      #endif
     #elif !HAS_CUSTOM_PROBE_PIN || Z_MAX_PIN != Z_MIN_PROBE_PIN
       // If this pin isn't the bed probe it's the Z endstop
       UPDATE_ENDSTOP_BIT(Z, MAX);
@@ -686,6 +729,16 @@ void Endstops::update() {
     } \
   }while(0)
 
+  #define PROCESS_QUAD_ENDSTOP(AXIS1, AXIS2, AXIS3, AXIS4, MINMAX) do { \
+    const byte quad_hit = TEST_ENDSTOP(_ENDSTOP(AXIS1, MINMAX)) | (TEST_ENDSTOP(_ENDSTOP(AXIS2, MINMAX)) << 1) | (TEST_ENDSTOP(_ENDSTOP(AXIS3, MINMAX)) << 2) | (TEST_ENDSTOP(_ENDSTOP(AXIS4, MINMAX)) << 3); \
+    if (quad_hit) { \
+      _ENDSTOP_HIT(AXIS1, MINMAX); \
+      /* if not performing home or if both endstops were trigged during homing... */ \
+      if (!stepper.separate_multi_axis || quad_hit == 0b1111) \
+        planner.endstop_triggered(_AXIS(AXIS1)); \
+    } \
+  }while(0)
+
   #if ENABLED(G38_PROBE_TARGET) && PIN_EXISTS(Z_MIN_PROBE) && !(CORE_IS_XY || CORE_IS_XZ)
     #if ENABLED(G38_PROBE_AWAY)
       #define _G38_OPEN_STATE (G38_move >= 4)
@@ -747,10 +800,14 @@ void Endstops::update() {
   if (stepper.axis_is_moving(Z_AXIS)) {
     if (stepper.motor_direction(Z_AXIS_HEAD)) { // Z -direction. Gantry down, bed up.
       #if HAS_Z_MIN || (Z_SPI_SENSORLESS && Z_HOME_DIR < 0)
-        #if ENABLED(Z_TRIPLE_ENDSTOPS)
+        #if ENABLED(Z_MULTI_ENDSTOPS)
+          #if NUM_Z_STEPPER_DRIVERS == 4
+            PROCESS_QUAD_ENDSTOP(Z, Z2, Z3, Z4, MIN);
+          #elif NUM_Z_STEPPER_DRIVERS == 3
             PROCESS_TRIPLE_ENDSTOP(Z, Z2, Z3, MIN);
-        #elif ENABLED(Z_DUAL_ENDSTOPS)
+          #else
             PROCESS_DUAL_ENDSTOP(Z, Z2, MIN);
+          #endif
         #else
           #if ENABLED(Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN)
             if (z_probe_enabled) PROCESS_ENDSTOP(Z, MIN);
@@ -769,10 +826,14 @@ void Endstops::update() {
     }
     else { // Z +direction. Gantry up, bed down.
       #if HAS_Z_MAX || (Z_SPI_SENSORLESS && Z_HOME_DIR > 0)
-        #if ENABLED(Z_TRIPLE_ENDSTOPS)
+        #if ENABLED(Z_MULTI_ENDSTOPS)
+          #if NUM_Z_STEPPER_DRIVERS == 4
+            PROCESS_QUAD_ENDSTOP(Z, Z2, Z3, Z4, MAX);
+          #elif NUM_Z_STEPPER_DRIVERS == 3
             PROCESS_TRIPLE_ENDSTOP(Z, Z2, Z3, MAX);
-        #elif ENABLED(Z_DUAL_ENDSTOPS)
+          #else
             PROCESS_DUAL_ENDSTOP(Z, Z2, MAX);
+          #endif
         #elif !HAS_CUSTOM_PROBE_PIN || Z_MAX_PIN != Z_MIN_PROBE_PIN
           // If this pin is not hijacked for the bed probe
           // then it belongs to the Z endstop
@@ -892,6 +953,12 @@ void Endstops::update() {
     #if HAS_Z3_MAX
       ES_GET_STATE(Z3_MAX);
     #endif
+    #if HAS_Z4_MIN
+      ES_GET_STATE(Z4_MIN);
+    #endif
+    #if HAS_Z4_MAX
+      ES_GET_STATE(Z4_MAX);
+    #endif
 
     uint16_t endstop_change = live_state_local ^ old_live_state_local;
     #define ES_REPORT_CHANGE(S) if (TEST(endstop_change, S)) SERIAL_ECHOPAIR("  " STRINGIFY(S) ":", TEST(live_state_local, S))
@@ -942,6 +1009,12 @@ void Endstops::update() {
       #if HAS_Z3_MAX
         ES_REPORT_CHANGE(Z3_MAX);
       #endif
+      #if HAS_Z4_MIN
+        ES_REPORT_CHANGE(Z4_MIN);
+      #endif
+      #if HAS_Z4_MAX
+        ES_REPORT_CHANGE(Z4_MAX);
+      #endif
       SERIAL_ECHOLNPGM("\n");
       analogWrite(pin_t(LED_PIN), local_LED_status);
       local_LED_status ^= 255;

Marlin/src/module/endstops.h

@@ -34,7 +34,8 @@ enum EndstopEnum : char {
   X2_MIN, X2_MAX,
   Y2_MIN, Y2_MAX,
   Z2_MIN, Z2_MAX,
-  Z3_MIN, Z3_MAX
+  Z3_MIN, Z3_MAX,
+  Z4_MIN, Z4_MAX
 };
 
 class Endstops {
@@ -47,12 +48,15 @@ class Endstops {
       #if ENABLED(Y_DUAL_ENDSTOPS)
         static float y2_endstop_adj;
       #endif
-      #if Z_MULTI_ENDSTOPS
+      #if ENABLED(Z_MULTI_ENDSTOPS)
         static float z2_endstop_adj;
       #endif
-      #if ENABLED(Z_TRIPLE_ENDSTOPS)
+      #if ENABLED(Z_MULTI_ENDSTOPS) && NUM_Z_STEPPER_DRIVERS >= 3
         static float z3_endstop_adj;
       #endif
+      #if ENABLED(Z_MULTI_ENDSTOPS) && NUM_Z_STEPPER_DRIVERS >= 4
+        static float z4_endstop_adj;
+      #endif
     #else
       typedef uint8_t esbits_t;
     #endif

Marlin/src/module/motion.cpp

@@ -1156,6 +1156,9 @@ feedRate_t get_homing_bump_feedrate(const AxisEnum axis) {
           #if AXIS_HAS_STALLGUARD(Z3)
             stealth_states.z3 = tmc_enable_stallguard(stepperZ3);
           #endif
+          #if AXIS_HAS_STALLGUARD(Z4)
+            stealth_states.z4 = tmc_enable_stallguard(stepperZ4);
+          #endif
           #if CORE_IS_XZ && X_SENSORLESS
             stealth_states.x = tmc_enable_stallguard(stepperX);
           #elif CORE_IS_YZ && Y_SENSORLESS
@@ -1225,6 +1228,9 @@ feedRate_t get_homing_bump_feedrate(const AxisEnum axis) {
           #if AXIS_HAS_STALLGUARD(Z3)
             tmc_disable_stallguard(stepperZ3, enable_stealth.z3);
           #endif
+          #if AXIS_HAS_STALLGUARD(Z4)
+            tmc_disable_stallguard(stepperZ4, enable_stealth.z4);
+          #endif
           #if CORE_IS_XZ && X_SENSORLESS
             tmc_disable_stallguard(stepperX, enable_stealth.x);
           #elif CORE_IS_YZ && Y_SENSORLESS
@@ -1509,7 +1515,7 @@ void homeaxis(const AxisEnum axis) {
       #if ENABLED(Y_DUAL_ENDSTOPS)
         case Y_AXIS:
       #endif
-      #if Z_MULTI_ENDSTOPS
+      #if ENABLED(Z_MULTI_ENDSTOPS)
         case Z_AXIS:
       #endif
       stepper.set_separate_multi_axis(true);
@@ -1593,8 +1599,12 @@ void homeaxis(const AxisEnum axis) {
         }
       }
     #endif
-    #if ENABLED(Z_DUAL_ENDSTOPS)
+
+    #if ENABLED(Z_MULTI_ENDSTOPS)
       if (axis == Z_AXIS) {
+
+        #if NUM_Z_STEPPER_DRIVERS == 2
+
           const float adj = ABS(endstops.z2_endstop_adj);
           if (adj) {
             if (pos_dir ? (endstops.z2_endstop_adj > 0) : (endstops.z2_endstop_adj < 0)) stepper.set_z_lock(true); else stepper.set_z2_lock(true);
@@ -1602,18 +1612,30 @@ void homeaxis(const AxisEnum axis) {
             stepper.set_z_lock(false);
             stepper.set_z2_lock(false);
           }
-      }
-    #endif
-    #if ENABLED(Z_TRIPLE_ENDSTOPS)
-      if (axis == Z_AXIS) {
-        // we push the function pointers for the stepper lock function into an array
-        void (*lock[3]) (bool)= {&stepper.set_z_lock, &stepper.set_z2_lock, &stepper.set_z3_lock};
-        float adj[3] = {0, endstops.z2_endstop_adj, endstops.z3_endstop_adj};
 
-        void (*tempLock) (bool);
+        #else
+
+          // Handy arrays of stepper lock function pointers
+
+          typedef void (*adjustFunc_t)(const bool);
+
+          adjustFunc_t lock[] = {
+            stepper.set_z_lock, stepper.set_z2_lock, stepper.set_z3_lock
+            #if NUM_Z_STEPPER_DRIVERS >= 4
+              , stepper.set_z4_lock
+            #endif
+          };
+          float adj[] = {
+            0, endstops.z2_endstop_adj, endstops.z3_endstop_adj
+            #if NUM_Z_STEPPER_DRIVERS >= 4
+              , endstops.z4_endstop_adj
+            #endif
+          };
+
+          adjustFunc_t tempLock;
           float tempAdj;
 
-        // manual bubble sort by adjust value
+          // Manual bubble sort by adjust value
           if (adj[1] < adj[0]) {
             tempLock = lock[0], tempAdj = adj[0];
             lock[0] = lock[1], adj[0] = adj[1];
@@ -1624,6 +1646,18 @@ void homeaxis(const AxisEnum axis) {
             lock[1] = lock[2], adj[1] = adj[2];
             lock[2] = tempLock, adj[2] = tempAdj;
           }
+          #if NUM_Z_STEPPER_DRIVERS >= 4
+            if (adj[3] < adj[2]) {
+              tempLock = lock[2], tempAdj = adj[2];
+              lock[2] = lock[3], adj[2] = adj[3];
+              lock[3] = tempLock, adj[3] = tempAdj;
+            }
+            if (adj[2] < adj[1]) {
+              tempLock = lock[1], tempAdj = adj[1];
+              lock[1] = lock[2], adj[1] = adj[2];
+              lock[2] = tempLock, adj[2] = tempAdj;
+            }
+          #endif
           if (adj[1] < adj[0]) {
             tempLock = lock[0], tempAdj = adj[0];
             lock[0] = lock[1], adj[0] = adj[1];
@@ -1637,8 +1671,17 @@ void homeaxis(const AxisEnum axis) {
             // lock the second stepper for the final correction
             (*lock[1])(true);
             do_homing_move(axis, adj[2] - adj[1]);
+            #if NUM_Z_STEPPER_DRIVERS >= 4
+              // lock the third stepper for the final correction
+              (*lock[2])(true);
+              do_homing_move(axis, adj[3] - adj[2]);
+            #endif
           }
           else {
+            #if NUM_Z_STEPPER_DRIVERS >= 4
+              (*lock[3])(true);
+              do_homing_move(axis, adj[2] - adj[3]);
+            #endif
             (*lock[2])(true);
             do_homing_move(axis, adj[1] - adj[2]);
             (*lock[1])(true);
@@ -1648,22 +1691,27 @@ void homeaxis(const AxisEnum axis) {
           stepper.set_z_lock(false);
           stepper.set_z2_lock(false);
           stepper.set_z3_lock(false);
+          #if NUM_Z_STEPPER_DRIVERS >= 4
+            stepper.set_z4_lock(false);
+          #endif
+
+        #endif
       }
     #endif
 
     // Reset flags for X, Y, Z motor locking
     switch (axis) {
+      default: break;
       #if ENABLED(X_DUAL_ENDSTOPS)
         case X_AXIS:
       #endif
       #if ENABLED(Y_DUAL_ENDSTOPS)
         case Y_AXIS:
       #endif
-      #if Z_MULTI_ENDSTOPS
+      #if ENABLED(Z_MULTI_ENDSTOPS)
         case Z_AXIS:
       #endif
           stepper.set_separate_multi_axis(false);
-      default: break;
     }
   #endif
 

Marlin/src/module/stepper.cpp

@@ -156,11 +156,16 @@ bool Stepper::abort_current_block;
 #if ENABLED(Y_DUAL_ENDSTOPS)
   bool Stepper::locked_Y_motor = false, Stepper::locked_Y2_motor = false;
 #endif
-#if Z_MULTI_ENDSTOPS || ENABLED(Z_STEPPER_AUTO_ALIGN)
+
-  bool Stepper::locked_Z_motor = false, Stepper::locked_Z2_motor = false;
+#if EITHER(Z_MULTI_ENDSTOPS, Z_STEPPER_AUTO_ALIGN)
-#endif
+  bool Stepper::locked_Z_motor = false, Stepper::locked_Z2_motor = false
-#if ENABLED(Z_TRIPLE_ENDSTOPS) || BOTH(Z_STEPPER_AUTO_ALIGN, Z_TRIPLE_STEPPER_DRIVERS)
+       #if NUM_Z_STEPPER_DRIVERS >= 3
-  bool Stepper::locked_Z3_motor = false;
+         , Stepper::locked_Z3_motor = false
+         #if NUM_Z_STEPPER_DRIVERS >= 4
+           , Stepper::locked_Z4_motor = false
+         #endif
+       #endif
+       ;
 #endif
 
 uint32_t Stepper::acceleration_time, Stepper::deceleration_time;
@@ -281,6 +286,42 @@ xyze_int8_t Stepper::count_direction{0};
     A##3_STEP_WRITE(V);                           \
   }
 
+#define QUAD_ENDSTOP_APPLY_STEP(A,V)                                                                                        \
+  if (separate_multi_axis) {                                                                                                \
+    if (A##_HOME_DIR < 0) {                                                                                                 \
+      if (!(TEST(endstops.state(), A##_MIN) && count_direction[_AXIS(A)] < 0) && !locked_##A##_motor) A##_STEP_WRITE(V);    \
+      if (!(TEST(endstops.state(), A##2_MIN) && count_direction[_AXIS(A)] < 0) && !locked_##A##2_motor) A##2_STEP_WRITE(V); \
+      if (!(TEST(endstops.state(), A##3_MIN) && count_direction[_AXIS(A)] < 0) && !locked_##A##3_motor) A##3_STEP_WRITE(V); \
+      if (!(TEST(endstops.state(), A##4_MIN) && count_direction[_AXIS(A)] < 0) && !locked_##A##4_motor) A##4_STEP_WRITE(V); \
+    }                                                                                                                       \
+    else {                                                                                                                  \
+      if (!(TEST(endstops.state(), A##_MAX) && count_direction[_AXIS(A)] > 0) && !locked_##A##_motor) A##_STEP_WRITE(V);    \
+      if (!(TEST(endstops.state(), A##2_MAX) && count_direction[_AXIS(A)] > 0) && !locked_##A##2_motor) A##2_STEP_WRITE(V); \
+      if (!(TEST(endstops.state(), A##3_MAX) && count_direction[_AXIS(A)] > 0) && !locked_##A##3_motor) A##3_STEP_WRITE(V); \
+      if (!(TEST(endstops.state(), A##4_MAX) && count_direction[_AXIS(A)] > 0) && !locked_##A##4_motor) A##4_STEP_WRITE(V); \
+    }                                                                                                                       \
+  }                                                                                                                         \
+  else {                                                                                                                    \
+    A##_STEP_WRITE(V);                                                                                                      \
+    A##2_STEP_WRITE(V);                                                                                                     \
+    A##3_STEP_WRITE(V);                                                                                                     \
+    A##4_STEP_WRITE(V);                                                                                                     \
+  }
+
+#define QUAD_SEPARATE_APPLY_STEP(A,V)             \
+  if (separate_multi_axis) {                      \
+    if (!locked_##A##_motor) A##_STEP_WRITE(V);   \
+    if (!locked_##A##2_motor) A##2_STEP_WRITE(V); \
+    if (!locked_##A##3_motor) A##3_STEP_WRITE(V); \
+    if (!locked_##A##4_motor) A##4_STEP_WRITE(V); \
+  }                                               \
+  else {                                          \
+    A##_STEP_WRITE(V);                            \
+    A##2_STEP_WRITE(V);                           \
+    A##3_STEP_WRITE(V);                           \
+    A##4_STEP_WRITE(V);                           \
+  }
+
 #if ENABLED(X_DUAL_STEPPER_DRIVERS)
   #define X_APPLY_DIR(v,Q) do{ X_DIR_WRITE(v); X2_DIR_WRITE((v) != INVERT_X2_VS_X_DIR); }while(0)
   #if ENABLED(X_DUAL_ENDSTOPS)
@@ -314,18 +355,27 @@ xyze_int8_t Stepper::count_direction{0};
   #define Y_APPLY_STEP(v,Q) Y_STEP_WRITE(v)
 #endif
 
-#if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+#if NUM_Z_STEPPER_DRIVERS == 4
+  #define Z_APPLY_DIR(v,Q) do{ Z_DIR_WRITE(v); Z2_DIR_WRITE(v); Z3_DIR_WRITE(v); Z4_DIR_WRITE(v); }while(0)
+  #if ENABLED(Z_MULTI_ENDSTOPS)
+    #define Z_APPLY_STEP(v,Q) QUAD_ENDSTOP_APPLY_STEP(Z,v)
+  #elif ENABLED(Z_STEPPER_AUTO_ALIGN)
+    #define Z_APPLY_STEP(v,Q) QUAD_SEPARATE_APPLY_STEP(Z,v)
+  #else
+    #define Z_APPLY_STEP(v,Q) do{ Z_STEP_WRITE(v); Z2_STEP_WRITE(v); Z3_STEP_WRITE(v); Z4_STEP_WRITE(v); }while(0)
+  #endif
+#elif NUM_Z_STEPPER_DRIVERS == 3
   #define Z_APPLY_DIR(v,Q) do{ Z_DIR_WRITE(v); Z2_DIR_WRITE(v); Z3_DIR_WRITE(v); }while(0)
-  #if ENABLED(Z_TRIPLE_ENDSTOPS)
+  #if ENABLED(Z_MULTI_ENDSTOPS)
     #define Z_APPLY_STEP(v,Q) TRIPLE_ENDSTOP_APPLY_STEP(Z,v)
   #elif ENABLED(Z_STEPPER_AUTO_ALIGN)
     #define Z_APPLY_STEP(v,Q) TRIPLE_SEPARATE_APPLY_STEP(Z,v)
   #else
     #define Z_APPLY_STEP(v,Q) do{ Z_STEP_WRITE(v); Z2_STEP_WRITE(v); Z3_STEP_WRITE(v); }while(0)
   #endif
-#elif ENABLED(Z_DUAL_STEPPER_DRIVERS)
+#elif NUM_Z_STEPPER_DRIVERS == 2
   #define Z_APPLY_DIR(v,Q) do{ Z_DIR_WRITE(v); Z2_DIR_WRITE(v); }while(0)
-  #if ENABLED(Z_DUAL_ENDSTOPS)
+  #if ENABLED(Z_MULTI_ENDSTOPS)
     #define Z_APPLY_STEP(v,Q) DUAL_ENDSTOP_APPLY_STEP(Z,v)
   #elif ENABLED(Z_STEPPER_AUTO_ALIGN)
     #define Z_APPLY_STEP(v,Q) DUAL_SEPARATE_APPLY_STEP(Z,v)
@@ -2062,12 +2112,15 @@ void Stepper::init() {
   #endif
   #if HAS_Z_DIR
     Z_DIR_INIT();
-    #if Z_MULTI_STEPPER_DRIVERS && HAS_Z2_DIR
+    #if NUM_Z_STEPPER_DRIVERS >= 2 && HAS_Z2_DIR
       Z2_DIR_INIT();
     #endif
-    #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS) && HAS_Z3_DIR
+    #if NUM_Z_STEPPER_DRIVERS >= 3 && HAS_Z3_DIR
       Z3_DIR_INIT();
     #endif
+    #if NUM_Z_STEPPER_DRIVERS >= 4 && HAS_Z4_DIR
+      Z4_DIR_INIT();
+    #endif
   #endif
   #if HAS_E0_DIR
     E0_DIR_INIT();
@@ -2108,14 +2161,18 @@ void Stepper::init() {
   #if HAS_Z_ENABLE
     Z_ENABLE_INIT();
     if (!Z_ENABLE_ON) Z_ENABLE_WRITE(HIGH);
-    #if Z_MULTI_STEPPER_DRIVERS && HAS_Z2_ENABLE
+    #if NUM_Z_STEPPER_DRIVERS >= 2 && HAS_Z2_ENABLE
       Z2_ENABLE_INIT();
       if (!Z_ENABLE_ON) Z2_ENABLE_WRITE(HIGH);
     #endif
-    #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS) && HAS_Z3_ENABLE
+    #if NUM_Z_STEPPER_DRIVERS >= 3 && HAS_Z3_ENABLE
       Z3_ENABLE_INIT();
       if (!Z_ENABLE_ON) Z3_ENABLE_WRITE(HIGH);
     #endif
+    #if NUM_Z_STEPPER_DRIVERS >= 4 && HAS_Z4_ENABLE
+      Z4_ENABLE_INIT();
+      if (!Z_ENABLE_ON) Z4_ENABLE_WRITE(HIGH);
+    #endif
   #endif
   #if HAS_E0_ENABLE
     E0_ENABLE_INIT();
@@ -2171,14 +2228,18 @@ void Stepper::init() {
   #endif
 
   #if HAS_Z_STEP
-    #if Z_MULTI_STEPPER_DRIVERS
+    #if NUM_Z_STEPPER_DRIVERS >= 2
       Z2_STEP_INIT();
       Z2_STEP_WRITE(INVERT_Z_STEP_PIN);
     #endif
-    #if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+    #if NUM_Z_STEPPER_DRIVERS >= 3
       Z3_STEP_INIT();
       Z3_STEP_WRITE(INVERT_Z_STEP_PIN);
     #endif
+    #if NUM_Z_STEPPER_DRIVERS >= 4
+      Z4_STEP_INIT();
+      Z4_STEP_WRITE(INVERT_Z_STEP_PIN);
+    #endif
     AXIS_INIT(Z, Z);
   #endif
 
@@ -2692,6 +2753,13 @@ void Stepper::report_positions() {
         SET_OUTPUT(Z3_MS3_PIN);
       #endif
     #endif
+    #if HAS_Z4_MICROSTEPS
+      SET_OUTPUT(Z4_MS1_PIN);
+      SET_OUTPUT(Z4_MS2_PIN);
+      #if PIN_EXISTS(Z4_MS3)
+        SET_OUTPUT(Z4_MS3_PIN);
+      #endif
+    #endif
     #if HAS_E0_MICROSTEPS
       SET_OUTPUT(E0_MS1_PIN);
       SET_OUTPUT(E0_MS2_PIN);
@@ -2762,7 +2830,7 @@ void Stepper::report_positions() {
           #endif
           break;
       #endif
-      #if HAS_Z_MICROSTEPS || HAS_Z2_MICROSTEPS || HAS_Z3_MICROSTEPS
+      #if HAS_SOME_Z_MICROSTEPS
         case 2:
           #if HAS_Z_MICROSTEPS
             WRITE(Z_MS1_PIN, ms1);
@@ -2773,6 +2841,9 @@ void Stepper::report_positions() {
           #if HAS_Z3_MICROSTEPS
             WRITE(Z3_MS1_PIN, ms1);
           #endif
+          #if HAS_Z4_MICROSTEPS
+            WRITE(Z4_MS1_PIN, ms1);
+          #endif
           break;
       #endif
       #if HAS_E0_MICROSTEPS
@@ -2815,7 +2886,7 @@ void Stepper::report_positions() {
           #endif
           break;
       #endif
-      #if HAS_Z_MICROSTEPS || HAS_Z2_MICROSTEPS || HAS_Z3_MICROSTEPS
+      #if HAS_SOME_Z_MICROSTEPS
         case 2:
           #if HAS_Z_MICROSTEPS
             WRITE(Z_MS2_PIN, ms2);
@@ -2826,6 +2897,9 @@ void Stepper::report_positions() {
           #if HAS_Z3_MICROSTEPS
             WRITE(Z3_MS2_PIN, ms2);
           #endif
+          #if HAS_Z4_MICROSTEPS
+            WRITE(Z4_MS2_PIN, ms2);
+          #endif
           break;
       #endif
       #if HAS_E0_MICROSTEPS
@@ -2868,7 +2942,7 @@ void Stepper::report_positions() {
           #endif
           break;
       #endif
-      #if HAS_Z_MICROSTEPS || HAS_Z2_MICROSTEPS || HAS_Z3_MICROSTEPS
+      #if HAS_SOME_Z_MICROSTEPS
         case 2:
           #if HAS_Z_MICROSTEPS && PIN_EXISTS(Z_MS3)
             WRITE(Z_MS3_PIN, ms3);
@@ -2879,6 +2953,9 @@ void Stepper::report_positions() {
           #if HAS_Z3_MICROSTEPS && PIN_EXISTS(Z3_MS3)
             WRITE(Z3_MS3_PIN, ms3);
           #endif
+          #if HAS_Z4_MICROSTEPS && PIN_EXISTS(Z4_MS3)
+            WRITE(Z4_MS3_PIN, ms3);
+          #endif
           break;
       #endif
       #if HAS_E0_MICROSTEPS && PIN_EXISTS(E0_MS3)

Marlin/src/module/stepper.h

@@ -274,11 +274,15 @@ class Stepper {
     #if ENABLED(Y_DUAL_ENDSTOPS)
       static bool locked_Y_motor, locked_Y2_motor;
     #endif
-    #if Z_MULTI_ENDSTOPS || ENABLED(Z_STEPPER_AUTO_ALIGN)
+    #if EITHER(Z_MULTI_ENDSTOPS, Z_STEPPER_AUTO_ALIGN)
-      static bool locked_Z_motor, locked_Z2_motor;
+      static bool locked_Z_motor, locked_Z2_motor
+                  #if NUM_Z_STEPPER_DRIVERS >= 3
+                    , locked_Z3_motor
+                    #if NUM_Z_STEPPER_DRIVERS >= 4
+                      , locked_Z4_motor
                     #endif
-    #if ENABLED(Z_TRIPLE_ENDSTOPS) || BOTH(Z_STEPPER_AUTO_ALIGN, Z_TRIPLE_STEPPER_DRIVERS)
+                  #endif
-      static bool locked_Z3_motor;
+                  ;
     #endif
 
     static uint32_t acceleration_time, deceleration_time; // time measured in Stepper Timer ticks
@@ -430,12 +434,15 @@ class Stepper {
       FORCE_INLINE static void set_y_lock(const bool state) { locked_Y_motor = state; }
       FORCE_INLINE static void set_y2_lock(const bool state) { locked_Y2_motor = state; }
     #endif
-    #if Z_MULTI_ENDSTOPS || (ENABLED(Z_STEPPER_AUTO_ALIGN) && Z_MULTI_STEPPER_DRIVERS)
+    #if EITHER(Z_MULTI_ENDSTOPS, Z_STEPPER_AUTO_ALIGN)
       FORCE_INLINE static void set_z_lock(const bool state) { locked_Z_motor = state; }
       FORCE_INLINE static void set_z2_lock(const bool state) { locked_Z2_motor = state; }
-    #endif
+      #if NUM_Z_STEPPER_DRIVERS >= 3
-    #if ENABLED(Z_TRIPLE_ENDSTOPS) || BOTH(Z_STEPPER_AUTO_ALIGN, Z_TRIPLE_STEPPER_DRIVERS)
         FORCE_INLINE static void set_z3_lock(const bool state) { locked_Z3_motor = state; }
+        #if NUM_Z_STEPPER_DRIVERS >= 4
+          FORCE_INLINE static void set_z4_lock(const bool state) { locked_Z4_motor = state; }
+        #endif
+      #endif
     #endif
 
     #if ENABLED(BABYSTEPPING)

Marlin/src/module/stepper/L64xx.cpp

@@ -52,6 +52,9 @@
 #if AXIS_IS_L64XX(Z3)
   L64XX_CLASS(Z3) stepperZ3(L6470_CHAIN_SS_PIN);
 #endif
+#if AXIS_IS_L64XX(Z4)
+  L64XX_CLASS(Z4) stepperZ4(L6470_CHAIN_SS_PIN);
+#endif
 #if AXIS_IS_L64XX(E0)
   L64XX_CLASS(E0) stepperE0(L6470_CHAIN_SS_PIN);
 #endif

Marlin/src/module/stepper/L64xx.h

@@ -160,6 +160,23 @@
   #endif
 #endif
 
+// Z4 Stepper
+#if HAS_Z4_ENABLE && AXIS_IS_L64XX(Z4)
+  extern L64XX_CLASS(Z4)         stepperZ4;
+  #define Z4_ENABLE_INIT()       NOOP
+  #define Z4_ENABLE_WRITE(STATE) (STATE ? NOOP : stepperZ4.free())
+  #define Z4_ENABLE_READ()       (stepperZ4.getStatus() & STATUS_HIZ)
+  #if AXIS_DRIVER_TYPE_Z4(L6474)
+    #define Z4_DIR_INIT()        SET_OUTPUT(Z4_DIR_PIN)
+    #define Z4_DIR_WRITE(STATE)  L6474_DIR_WRITE(Z4, STATE)
+    #define Z4_DIR_READ()        READ(Z4_DIR_PIN)
+  #else
+    #define Z4_DIR_INIT()        NOOP
+    #define Z4_DIR_WRITE(STATE)  L64XX_DIR_WRITE(Z4, STATE)
+    #define Z4_DIR_READ()        (stepper##Z4.getStatus() & STATUS_DIR);
+  #endif
+#endif
+
 // E0 Stepper
 #if AXIS_IS_L64XX(E0)
   extern L64XX_CLASS(E0)         stepperE0;

Marlin/src/module/stepper/TMC26X.cpp

@@ -57,6 +57,9 @@
 #if AXIS_DRIVER_TYPE_Z3(TMC26X)
   _TMC26X_DEFINE(Z3);
 #endif
+#if AXIS_DRIVER_TYPE_Z4(TMC26X)
+  _TMC26X_DEFINE(Z4);
+#endif
 #if AXIS_DRIVER_TYPE_E0(TMC26X)
   _TMC26X_DEFINE(E0);
 #endif
@@ -103,6 +106,9 @@ void tmc26x_init_to_defaults() {
   #if AXIS_DRIVER_TYPE_Z3(TMC26X)
     _TMC26X_INIT(Z3);
   #endif
+  #if AXIS_DRIVER_TYPE_Z4(TMC26X)
+    _TMC26X_INIT(Z4);
+  #endif
   #if AXIS_DRIVER_TYPE_E0(TMC26X)
     _TMC26X_INIT(E0);
   #endif

Marlin/src/module/stepper/TMC26X.h

@@ -95,6 +95,14 @@ void tmc26x_init_to_defaults();
   #define Z3_ENABLE_READ() stepperZ3.isEnabled()
 #endif
 
+// Z4 Stepper
+#if HAS_Z4_ENABLE && AXIS_DRIVER_TYPE_Z4(TMC26X)
+  extern TMC26XStepper stepperZ4;
+  #define Z4_ENABLE_INIT() NOOP
+  #define Z4_ENABLE_WRITE(STATE) stepperZ4.setEnabled(STATE)
+  #define Z4_ENABLE_READ() stepperZ4.isEnabled()
+#endif
+
 // E0 Stepper
 #if AXIS_DRIVER_TYPE_E0(TMC26X)
   extern TMC26XStepper stepperE0;

Marlin/src/module/stepper/indirection.h

@@ -180,6 +180,27 @@ void reset_stepper_drivers();    // Called by settings.load / settings.reset
   #define Z3_DIR_WRITE(STATE) NOOP
 #endif
 
+// Z4 Stepper
+#if HAS_Z4_ENABLE
+  #ifndef Z4_ENABLE_INIT
+    #define Z4_ENABLE_INIT() SET_OUTPUT(Z4_ENABLE_PIN)
+    #define Z4_ENABLE_WRITE(STATE) WRITE(Z4_ENABLE_PIN,STATE)
+    #define Z4_ENABLE_READ() READ(Z4_ENABLE_PIN)
+  #endif
+  #ifndef Z4_DIR_INIT
+    #define Z4_DIR_INIT() SET_OUTPUT(Z4_DIR_PIN)
+    #define Z4_DIR_WRITE(STATE) WRITE(Z4_DIR_PIN,STATE)
+    #define Z4_DIR_READ() READ(Z4_DIR_PIN)
+  #endif
+  #define Z4_STEP_INIT SET_OUTPUT(Z4_STEP_PIN)
+  #ifndef Z4_STEP_WRITE
+    #define Z4_STEP_WRITE(STATE) WRITE(Z4_STEP_PIN,STATE)
+  #endif
+  #define Z4_STEP_READ READ(Z4_STEP_PIN)
+#else
+  #define Z4_DIR_WRITE(STATE) NOOP
+#endif
+
 // E0 Stepper
 #ifndef E0_ENABLE_INIT
   #define E0_ENABLE_INIT() SET_OUTPUT(E0_ENABLE_PIN)
@@ -491,8 +512,20 @@ void reset_stepper_drivers();    // Called by settings.load / settings.reset
   #define Z3_disable() NOOP
 #endif
 
-#define  enable_Z() do{ Z_enable();  Z2_enable();  Z3_enable();  }while(0)
+#if AXIS_DRIVER_TYPE_Z4(L6470)
-#define disable_Z() do{ Z_disable(); Z2_disable(); Z3_disable(); CBI(axis_known_position, Z_AXIS); }while(0)
+  extern L6470 stepperZ4;
+  #define Z4_enable()  NOOP
+  #define Z4_disable() stepperZ4.free()
+#elif HAS_Z4_ENABLE
+  #define Z4_enable()  Z4_ENABLE_WRITE( Z_ENABLE_ON)
+  #define Z4_disable() Z4_ENABLE_WRITE(!Z_ENABLE_ON)
+#else
+  #define Z4_enable()  NOOP
+  #define Z4_disable() NOOP
+#endif
+
+#define  enable_Z() do{ Z_enable();  Z2_enable();  Z3_enable();  Z4_enable(); }while(0)
+#define disable_Z() do{ Z_disable(); Z2_disable(); Z3_disable(); Z4_disable(); CBI(axis_known_position, Z_AXIS); }while(0)
 
 //
 // Extruder Stepper enable / disable

Marlin/src/module/stepper/trinamic.cpp

@@ -88,6 +88,9 @@ enum StealthIndex : uint8_t { STEALTH_AXIS_XY, STEALTH_AXIS_Z, STEALTH_AXIS_E };
 #if AXIS_HAS_SPI(Z3)
   TMC_SPI_DEFINE(Z3, Z);
 #endif
+#if AXIS_HAS_SPI(Z4)
+  TMC_SPI_DEFINE(Z4, Z);
+#endif
 #if AXIS_HAS_SPI(E0)
   TMC_SPI_DEFINE_E(0);
 #endif
@@ -249,6 +252,13 @@ enum StealthIndex : uint8_t { STEALTH_AXIS_XY, STEALTH_AXIS_Z, STEALTH_AXIS_E };
       TMC_UART_DEFINE(SW, Z3, Z);
     #endif
   #endif
+  #if AXIS_HAS_UART(Z4)
+    #ifdef Z4_HARDWARE_SERIAL
+      TMC_UART_DEFINE(HW, Z4, Z);
+    #else
+      TMC_UART_DEFINE(SW, Z4, Z);
+    #endif
+  #endif
   #if AXIS_HAS_UART(E0)
     #ifdef E0_HARDWARE_SERIAL
       TMC_UART_DEFINE_E(HW, 0);
@@ -342,6 +352,13 @@ enum StealthIndex : uint8_t { STEALTH_AXIS_XY, STEALTH_AXIS_Z, STEALTH_AXIS_E };
         stepperZ3.beginSerial(TMC_BAUD_RATE);
       #endif
     #endif
+    #if AXIS_HAS_UART(Z4)
+      #ifdef Z4_HARDWARE_SERIAL
+        Z4_HARDWARE_SERIAL.begin(TMC_BAUD_RATE);
+      #else
+        stepperZ4.beginSerial(TMC_BAUD_RATE);
+      #endif
+    #endif
     #if AXIS_HAS_UART(E0)
       #ifdef E0_HARDWARE_SERIAL
         E0_HARDWARE_SERIAL.begin(TMC_BAUD_RATE);
@@ -616,6 +633,9 @@ void restore_trinamic_drivers() {
   #if AXIS_IS_TMC(Z3)
     stepperZ3.push();
   #endif
+  #if AXIS_IS_TMC(Z4)
+    stepperZ4.push();
+  #endif
   #if AXIS_IS_TMC(E0)
     stepperE0.push();
   #endif
@@ -678,6 +698,9 @@ void reset_trinamic_drivers() {
   #if AXIS_IS_TMC(Z3)
     _TMC_INIT(Z3, STEALTH_AXIS_Z);
   #endif
+  #if AXIS_IS_TMC(Z4)
+    _TMC_INIT(Z4, STEALTH_AXIS_Z);
+  #endif
   #if AXIS_IS_TMC(E0)
     _TMC_INIT(E0, STEALTH_AXIS_E);
   #endif
@@ -727,6 +750,9 @@ void reset_trinamic_drivers() {
       #if AXIS_HAS_STALLGUARD(Z3)
         stepperZ3.homing_threshold(Z_STALL_SENSITIVITY);
       #endif
+      #if AXIS_HAS_STALLGUARD(Z4)
+        stepperZ4.homing_threshold(Z_STALL_SENSITIVITY);
+      #endif
     #endif
   #endif
 

Marlin/src/module/stepper/trinamic.h

@@ -50,6 +50,7 @@
 #define TMC_Y2_LABEL 'Y', '2'
 #define TMC_Z2_LABEL 'Z', '2'
 #define TMC_Z3_LABEL 'Z', '3'
+#define TMC_Z4_LABEL 'Z', '4'
 
 #define TMC_E0_LABEL 'E', '0'
 #define TMC_E1_LABEL 'E', '1'
@@ -175,6 +176,19 @@ void reset_trinamic_drivers();
   #endif
 #endif
 
+// Z4 Stepper
+#if HAS_Z4_ENABLE && AXIS_IS_TMC(Z4)
+  extern TMC_CLASS(Z4, Z) stepperZ4;
+  #if ENABLED(SOFTWARE_DRIVER_ENABLE)
+    #define Z4_ENABLE_INIT() NOOP
+    #define Z4_ENABLE_WRITE(STATE) stepperZ4.toff((STATE)==Z_ENABLE_ON ? chopper_timing.toff : 0)
+    #define Z4_ENABLE_READ() stepperZ4.isEnabled()
+  #endif
+  #if AXIS_HAS_SQUARE_WAVE(Z4)
+    #define Z4_STEP_WRITE(STATE) do{ if(STATE) TOGGLE(Z4_STEP_PIN); }while(0)
+  #endif
+#endif
+
 // E0 Stepper
 #if AXIS_IS_TMC(E0)
   extern TMC_CLASS_E(0) stepperE0;

Marlin/src/pins/pins.h

@@ -1153,7 +1153,7 @@
 #endif
 
 // The Z2 axis, if any, should be the next open extruder port
-#if Z_MULTI_STEPPER_DRIVERS
+#if NUM_Z_STEPPER_DRIVERS >= 2
   #ifndef Z2_STEP_PIN
     #define Z2_STEP_PIN   _EPIN(Z2_E_INDEX, STEP)
     #define Z2_DIR_PIN    _EPIN(Z2_E_INDEX, DIR)
@@ -1200,7 +1200,7 @@
   #define Z2_MS3_PIN -1
 #endif
 
-#if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+#if NUM_Z_STEPPER_DRIVERS >= 3
   #ifndef Z3_STEP_PIN
     #define Z3_STEP_PIN   _EPIN(Z3_E_INDEX, STEP)
     #define Z3_DIR_PIN    _EPIN(Z3_E_INDEX, DIR)
@@ -1231,6 +1231,7 @@
       #define Z3_SERIAL_RX_PIN _EPIN(Z3_E_INDEX, SERIAL_RX)
     #endif
   #endif
+  #define Z4_E_INDEX INCREMENT(Z3_E_INDEX)
 #endif
 
 #ifndef Z3_CS_PIN
@@ -1246,6 +1247,52 @@
   #define Z3_MS3_PIN -1
 #endif
 
+#if NUM_Z_STEPPER_DRIVERS >= 4
+  #ifndef Z4_STEP_PIN
+    #define Z4_STEP_PIN   _EPIN(Z4_E_INDEX, STEP)
+    #define Z4_DIR_PIN    _EPIN(Z4_E_INDEX, DIR)
+    #define Z4_ENABLE_PIN _EPIN(Z4_E_INDEX, ENABLE)
+    #if Z4_E_INDEX >= MAX_EXTRUDERS || !PIN_EXISTS(Z4_STEP)
+      #error "No E stepper plug left for Z4!"
+    #endif
+  #endif
+  #if AXIS_HAS_SPI(Z4)
+    #ifndef Z4_CS_PIN
+      #define Z4_CS_PIN     _EPIN(Z4_E_INDEX, CS)
+    #endif
+  #endif
+  #ifndef Z4_MS1_PIN
+    #define Z4_MS1_PIN    _EPIN(Z4_E_INDEX, MS1)
+  #endif
+  #ifndef Z4_MS2_PIN
+    #define Z4_MS2_PIN    _EPIN(Z4_E_INDEX, MS2)
+  #endif
+  #ifndef Z4_MS3_PIN
+    #define Z4_MS3_PIN    _EPIN(Z4_E_INDEX, MS3)
+  #endif
+  #if AXIS_HAS_UART(Z4)
+    #ifndef Z4_SERIAL_TX_PIN
+      #define Z4_SERIAL_TX_PIN _EPIN(Z4_E_INDEX, SERIAL_TX)
+    #endif
+    #ifndef Z4_SERIAL_RX_PIN
+      #define Z4_SERIAL_RX_PIN _EPIN(Z4_E_INDEX, SERIAL_RX)
+    #endif
+  #endif
+#endif
+
+#ifndef Z4_CS_PIN
+  #define Z4_CS_PIN  -1
+#endif
+#ifndef Z4_MS1_PIN
+  #define Z4_MS1_PIN -1
+#endif
+#ifndef Z4_MS2_PIN
+  #define Z4_MS2_PIN -1
+#endif
+#ifndef Z4_MS3_PIN
+  #define Z4_MS3_PIN -1
+#endif
+
 #if HAS_GRAPHICAL_LCD
   #if !defined(ST7920_DELAY_1) && defined(BOARD_ST7920_DELAY_1)
     #define ST7920_DELAY_1 BOARD_ST7920_DELAY_1

Marlin/src/pins/pinsDebug_list.h

@@ -90,6 +90,15 @@
 #if !PIN_EXISTS(Z3_MS3)
   #undef Z3_MS3_PIN
 #endif
+#if !PIN_EXISTS(Z4_MS1)
+  #undef Z4_MS1_PIN
+#endif
+#if !PIN_EXISTS(Z4_MS2)
+  #undef Z4_MS2_PIN
+#endif
+#if !PIN_EXISTS(Z4_MS3)
+  #undef Z4_MS3_PIN
+#endif
 #if !PIN_EXISTS(E0_MS1)
   #undef E0_MS1_PIN
 #endif
@@ -1335,6 +1344,27 @@
 #if PIN_EXISTS(Z3_STEP)
   REPORT_NAME_DIGITAL(__LINE__, Z3_STEP_PIN)
 #endif
+#if PIN_EXISTS(Z4_CS)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_CS_PIN)
+#endif
+#if PIN_EXISTS(Z4_DIR)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_DIR_PIN)
+#endif
+#if PIN_EXISTS(Z4_ENABLE)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_ENABLE_PIN)
+#endif
+#if PIN_EXISTS(Z4_MS1)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_MS1_PIN)
+#endif
+#if PIN_EXISTS(Z4_MS2)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_MS2_PIN)
+#endif
+#if PIN_EXISTS(Z4_MS3)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_MS3_PIN)
+#endif
+#if PIN_EXISTS(Z4_STEP)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_STEP_PIN)
+#endif
 #if PIN_EXISTS(ZRIB_V20_D6)
   REPORT_NAME_DIGITAL(__LINE__, ZRIB_V20_D6_PIN)
 #endif
@@ -1383,6 +1413,12 @@
 #if PIN_EXISTS(Z3_SERIAL_RX)
   REPORT_NAME_DIGITAL(__LINE__, Z3_SERIAL_RX_PIN)
 #endif
+#if PIN_EXISTS(Z4_SERIAL_TX)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_SERIAL_TX_PIN)
+#endif
+#if PIN_EXISTS(Z4_SERIAL_RX)
+  REPORT_NAME_DIGITAL(__LINE__, Z4_SERIAL_RX_PIN)
+#endif
 #if PIN_EXISTS(E0_SERIAL_TX)
   REPORT_NAME_DIGITAL(__LINE__, E0_SERIAL_TX_PIN)
 #endif

Marlin/src/pins/ramps/pins_RL200.h

@@ -31,13 +31,9 @@
 
 #if HOTENDS > 2 || E_STEPPERS > 2
   #error "RL200v1 supports up to 2 hotends / E-steppers. Comment out this line to continue."
-#endif
+#elif NUM_Z_STEPPER_DRIVERS != 2
-
+  #error "RL200 uses dual Z stepper motors. Set NUM_Z_STEPPER_DRIVERS to 2 or comment out this line to continue."
-#if DISABLED(Z_DUAL_STEPPER_DRIVERS)
+#elif !(AXIS_DRIVER_TYPE_X(DRV8825) && AXIS_DRIVER_TYPE_Y(DRV8825) && AXIS_DRIVER_TYPE_Z(DRV8825) && AXIS_DRIVER_TYPE_Z2(DRV8825) && AXIS_DRIVER_TYPE_E0(DRV8825))
-  #error "RL200 uses dual Z stepper motors. Update Configuration_adv.h or comment out this line to continue."
-#endif
-
-#if !(AXIS_DRIVER_TYPE_X(DRV8825) && AXIS_DRIVER_TYPE_Y(DRV8825) && AXIS_DRIVER_TYPE_Z(DRV8825) && AXIS_DRIVER_TYPE_Z2(DRV8825) && AXIS_DRIVER_TYPE_E0(DRV8825))
   #error "You must set ([XYZ]|Z2|E0)_DRIVER_TYPE to DRV8825 in Configuration.h for RL200."
 #endif
 

Marlin/src/pins/sensitive_pins.h

@@ -423,7 +423,7 @@
   #define _Y2_PINS
 #endif
 
-#if Z_MULTI_STEPPER_DRIVERS
+#if NUM_Z_STEPPER_DRIVERS >= 2
   #if PIN_EXISTS(Z2_CS) && AXIS_HAS_SPI(Z2)
     #define _Z2_CS Z2_CS_PIN,
   #else
@@ -449,7 +449,7 @@
   #define _Z2_PINS
 #endif
 
-#if ENABLED(Z_TRIPLE_STEPPER_DRIVERS)
+#if NUM_Z_STEPPER_DRIVERS >= 3
   #if PIN_EXISTS(Z3_CS) && AXIS_HAS_SPI(Z3)
     #define _Z3_CS Z3_CS_PIN,
   #else
@@ -475,6 +475,32 @@
   #define _Z3_PINS
 #endif
 
+#if NUM_Z_STEPPER_DRIVERS >= 4
+  #if PIN_EXISTS(Z4_CS) && AXIS_HAS_SPI(Z4)
+    #define _Z4_CS Z4_CS_PIN,
+  #else
+    #define _Z4_CS
+  #endif
+  #if PIN_EXISTS(Z4_MS1)
+    #define _Z4_MS1 Z4_MS1_PIN,
+  #else
+    #define _Z4_MS1
+  #endif
+  #if PIN_EXISTS(Z4_MS2)
+    #define _Z4_MS2 Z4_MS2_PIN,
+  #else
+    #define _Z4_MS2
+  #endif
+  #if PIN_EXISTS(Z4_MS3)
+    #define _Z4_MS3 Z4_MS3_PIN,
+  #else
+    #define _Z4_MS3
+  #endif
+  #define _Z4_PINS Z4_STEP_PIN, Z4_DIR_PIN, Z4_ENABLE_PIN, _Z4_CS _Z4_MS1 _Z4_MS2 _Z4_MS3
+#else
+  #define _Z4_PINS
+#endif
+
 //
 // Generate the final Sensitive Pins array,
 // keeping the array as small as possible.
@@ -524,9 +550,9 @@
 #endif
 
 #define SENSITIVE_PINS { \
-  _X_PINS _Y_PINS _Z_PINS _X2_PINS _Y2_PINS _Z2_PINS _Z3_PINS _Z_PROBE \
+  _X_PINS _Y_PINS _Z_PINS _X2_PINS _Y2_PINS _Z2_PINS _Z3_PINS _Z4_PINS \
-  _E0_PINS _E1_PINS _E2_PINS _E3_PINS _E4_PINS _E5_PINS _BED_PINS \
+  _Z_PROBE _E0_PINS _E1_PINS _E2_PINS _E3_PINS _E4_PINS _E5_PINS \
-  _H0_PINS _H1_PINS _H2_PINS _H3_PINS _H4_PINS _H5_PINS \
+  _BED_PINS _H0_PINS _H1_PINS _H2_PINS _H3_PINS _H4_PINS _H5_PINS \
   _PS_ON _HEATER_BED _FAN0 _FAN1 _FAN2 _FANC \
   HAL_SENSITIVE_PINS \
 }

buildroot/share/tests/DUE-tests

@@ -37,16 +37,16 @@ exec_test $1 $2 "RAMPS4DUE_EFB with ABL (Bilinear), EXTENSIBLE_UI, S-Curve, many
 restore_configs
 opt_set MOTHERBOARD BOARD_RADDS
 opt_enable USE_XMAX_PLUG USE_YMAX_PLUG ENDSTOPPULLUPS BLTOUCH AUTO_BED_LEVELING_BILINEAR \
-           Z_TRIPLE_STEPPER_DRIVERS Z_TRIPLE_ENDSTOPS Z_STEPPER_AUTO_ALIGN \
+           Z_MULTI_ENDSTOPS Z_STEPPER_AUTO_ALIGN Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS
-           Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS
            #TOUCH_UI_FTDI_EVE LCD_ALEPHOBJECTS_CLCD_UI OTHER_PIN_LAYOUT
+opt_set NUM_Z_STEPPER_DRIVERS 3
 opt_add Z2_MAX_ENDSTOP_INVERTING false
 opt_add Z3_MAX_ENDSTOP_INVERTING false
-pins_set ramps/RAMPS X_MAX_PIN -1
-pins_set ramps/RAMPS Y_MAX_PIN -1
 opt_add Z2_MAX_PIN 2
 opt_add Z3_MAX_PIN 3
-exec_test $1 $2 "RADDS with ABL (Bilinear), Z_TRIPLE_STEPPER_DRIVERS and Z_STEPPER_AUTO_ALIGN"
+pins_set ramps/RAMPS X_MAX_PIN -1
+pins_set ramps/RAMPS Y_MAX_PIN -1
+exec_test $1 $2 "RADDS with ABL (Bilinear), Triple Z Axis, Z_STEPPER_AUTO_ALIGN"
 
 #
 # Test SWITCHING_EXTRUDER

buildroot/share/tests/teensy35-tests

@@ -100,15 +100,16 @@ opt_enable COREXZ
 exec_test $1 $2 "COREXZ"
 
 #
-# Enable Z_DUAL_STEPPER_DRIVERS, Z_DUAL_ENDSTOPS
+# Enable Dual Z with Dual Z endstops
 #
 restore_configs
 opt_set MOTHERBOARD BOARD_TEENSY35_36
-opt_enable Z_DUAL_STEPPER_DRIVERS Z_DUAL_ENDSTOPS
+opt_enable Z_MULTI_ENDSTOPS
+opt_set NUM_Z_STEPPER_DRIVERS 2
 pins_set ramps/RAMPS X_MAX_PIN -1
 opt_add Z2_MAX_PIN 2
 opt_enable USE_XMAX_PLUG
-exec_test $1 $2 "Z_DUAL_STEPPER_DRIVERS, Z_DUAL_ENDSTOPS"
+exec_test $1 $2 "Dual Z with Dual Z endstops"
 
 # Clean up
 restore_configs