Merge a769ffeaec into d22e61a12c

Marlin/Configuration.h

@@ -2169,6 +2169,13 @@
 //#define AUTO_BED_LEVELING_UBL
 //#define MESH_BED_LEVELING
 
+/**
+ * Base the Probe Z Offset on a trustworthy Z endstop
+ * Requires the Z axis to be homed with an endstop.
+ * Use 'M206 Z' to adjust the Z endstop to match the height at bed center.
+ */
+//#define AUTO_Z_PROBE_OFFSET
+
 /**
  * Commands to execute at the start of G29 probing,
  * after switching to the PROBING_TOOL.

Marlin/src/feature/bedlevel/ubl/ubl_G29.cpp

@@ -318,16 +318,28 @@ void unified_bed_leveling::G29() {
   // Check for commands that require the printer to be homed
   if (may_move) {
     planner.synchronize();
-    #if ALL(DWIN_LCD_PROUI, ZHOME_BEFORE_LEVELING)
-      save_ubl_active_state_and_disable();
-      gcode.process_subcommands_now(F("G28Z"));
-      restore_ubl_active_state(false); // ...without telling ExtUI "done"
-    #else
-      // Send 'N' to force homing before G29 (internal only)
-      if (axes_should_home() || parser.seen_test('N')) gcode.home_all_axes();
-    #endif
+
+    // Send 'N' to force homing before G29 (internal only)
+    const bool force_home = axes_should_home() || parser.seen_test('N');
+    if (force_home) {
+      gcode.home_all_axes();
+    }
+    else {
+      #if ALL(DWIN_LCD_PROUI, ZHOME_BEFORE_LEVELING)
+        save_ubl_active_state_and_disable();
+        gcode.process_subcommands_now(F("G28Z"));
+        restore_ubl_active_state(false);              // ...without telling ExtUI "done"
+      #elif ENABLED(AUTO_Z_PROBE_OFFSET)
+        gcode.process_subcommands_now(F("G28XYL0"));  // Home X and Y only
+      #endif
+    }
+
     probe.use_probing_tool();
 
+    #if ENABLED(AUTO_Z_PROBE_OFFSET)
+      (void)probe.probe_to_obtain_z_offset();
+    #endif
+
     #ifdef EVENT_GCODE_BEFORE_G29
       if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPGM("Before G29 G-code: ", EVENT_GCODE_BEFORE_G29);
       gcode.process_subcommands_now(F(EVENT_GCODE_BEFORE_G29));

Marlin/src/gcode/bedlevel/abl/G29.cpp

@@ -292,6 +292,10 @@ G29_TYPE GcodeSuite::G29() {
       gcode.process_subcommands_now(F(EVENT_GCODE_BEFORE_G29));
     #endif
 
+    #if ENABLED(AUTO_Z_PROBE_OFFSET)
+      (void)probe.probe_to_obtain_z_offset();
+    #endif
+
     #if ANY(PROBE_MANUALLY, AUTO_BED_LEVELING_LINEAR)
       abl.abl_probe_index = -1;
     #endif
@@ -588,7 +592,7 @@ G29_TYPE GcodeSuite::G29() {
         abl.z_values[abl.meshCount.x][abl.meshCount.y] = newz;
         TERN_(EXTENSIBLE_UI, ExtUI::onMeshUpdate(abl.meshCount, newz));
 
-        if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPGM_P(PSTR("Save X"), abl.meshCount.x, SP_Y_STR, abl.meshCount.y, SP_Z_STR, abl.measured_z + abl.Z_offset);
+        if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPGM_P(PSTR("Save X"), abl.meshCount.x, SP_Y_STR, abl.meshCount.y, SP_Z_STR, newz);
 
       #endif
     }

Marlin/src/inc/SanityCheck.h

@@ -2544,6 +2544,8 @@ static_assert(NUM_SERVOS <= NUM_SERVO_PLUGS, "NUM_SERVOS (or some servo index) i
   #error "Z_HOME_DIR must be -1 when homing Z with the probe."
 #elif ALL(USE_PROBE_FOR_Z_HOMING, HOME_Z_FIRST)
   #error "HOME_Z_FIRST can't be used when homing Z with a probe."
+#elif ALL(USE_PROBE_FOR_Z_HOMING, AUTO_Z_PROBE_OFFSET)
+  #error "AUTO_Z_PROBE_OFFSET requires Z Endstop Homing."
 #endif
 
 #if Z_HOME_TO_MAX && defined(Z_AFTER_HOMING) && DISABLED(ALLOW_Z_AFTER_HOMING)

Marlin/src/module/probe.cpp

@@ -763,6 +763,25 @@ bool Probe::probe_down_to_z(const float z, const feedRate_t fr_mm_s) {
   }
 #endif
 
+#if ENABLED(AUTO_Z_PROBE_OFFSET)
+
+  // Determine the probe.offset.z based on the trusted Z0
+  // Return 'true' on error condition.
+  bool Probe::probe_to_obtain_z_offset() {
+    use_probing_tool();
+    do_z_clearance(Z_CLEARANCE_DEPLOY_PROBE);
+    const xy_pos_t ref_xy = {
+      TERN(Z_SAFE_HOMING, Z_SAFE_HOMING_X_POINT, X_CENTER),
+      TERN(Z_SAFE_HOMING, Z_SAFE_HOMING_Y_POINT, Y_CENTER)
+    };
+    const float zval = probe_at_point(ref_xy, PROBE_PT_RAISE);
+    if (zval == NAN) return true;
+    offset.z = -zval;
+    return false;
+  }
+
+#endif // AUTO_Z_PROBE_OFFSET
+
 /**
  * @brief Probe at the current XY (possibly more than once) to find the bed Z.
  *

Marlin/src/module/probe.h

@@ -363,6 +363,10 @@ public:
     static bool tare();
   #endif
 
+  #if ENABLED(AUTO_Z_PROBE_OFFSET)
+    static bool probe_to_obtain_z_offset();
+  #endif
+
   // Basic functions for Sensorless Homing and Probing
   #if HAS_DELTA_SENSORLESS_PROBING
     static void set_offset_sensorless_adj(const float sz);