Reverse the sign of zprobe_zoffset

- When editing on the LCD, minus now means below the nozzle
- Stores the opposite sign in EEPROM, so bumped to “V20”

Marlin/Marlin_main.cpp

@@ -286,7 +286,7 @@ bool target_direction;
 
 #ifdef ENABLE_AUTO_BED_LEVELING
   int xy_travel_speed = XY_TRAVEL_SPEED;
-  float zprobe_zoffset = -Z_PROBE_OFFSET_FROM_EXTRUDER;
+  float zprobe_zoffset = Z_PROBE_OFFSET_FROM_EXTRUDER;
 #endif
 
 #if defined(Z_DUAL_ENDSTOPS) && !defined(DELTA)
@@ -1060,7 +1060,7 @@ static void axis_is_at_home(AxisEnum axis) {
     max_pos[axis] = base_max_pos(axis) + home_offset[axis];
 
     #if defined(ENABLE_AUTO_BED_LEVELING) && Z_HOME_DIR < 0
-      if (axis == Z_AXIS) current_position[Z_AXIS] += zprobe_zoffset;
+      if (axis == Z_AXIS) current_position[Z_AXIS] -= zprobe_zoffset;
     #endif
   }
 }
@@ -4648,7 +4648,7 @@ inline void gcode_M400() { st_synchronize(); }
   #ifdef SERVO_ENDSTOPS
     void raise_z_for_servo() {
       float zpos = current_position[Z_AXIS], z_dest = Z_RAISE_BEFORE_HOMING;
-      z_dest += axis_known_position[Z_AXIS] ? -zprobe_zoffset : zpos;
+      z_dest += axis_known_position[Z_AXIS] ? zprobe_zoffset : zpos;
       if (zpos < z_dest)
         do_blocking_move_to(current_position[X_AXIS], current_position[Y_AXIS], z_dest); // also updates current_position
     }
@@ -4869,7 +4869,7 @@ inline void gcode_M503() {
     if (code_seen('Z')) {
       value = code_value();
       if (Z_PROBE_OFFSET_RANGE_MIN <= value && value <= Z_PROBE_OFFSET_RANGE_MAX) {
-        zprobe_zoffset = -value;
+        zprobe_zoffset = value;
         SERIAL_ECHO_START;
         SERIAL_ECHOLNPGM(MSG_ZPROBE_ZOFFSET " " MSG_OK);
         SERIAL_EOL;
@@ -4886,8 +4886,8 @@ inline void gcode_M503() {
     }
     else {
       SERIAL_ECHO_START;
-      SERIAL_ECHOLNPGM(MSG_ZPROBE_ZOFFSET " : ");
-      SERIAL_ECHO(-zprobe_zoffset);
+      SERIAL_ECHOPGM(MSG_ZPROBE_ZOFFSET " : ");
+      SERIAL_ECHO(zprobe_zoffset);
       SERIAL_EOL;
     }
   }

Marlin/configuration_store.cpp

@@ -14,7 +14,7 @@
  *
  */
 
-#define EEPROM_VERSION "V19"
+#define EEPROM_VERSION "V20"
 
 /**
  * V19 EEPROM Layout:
@@ -499,7 +499,7 @@ void Config_ResetDefault() {
   #endif
 
   #ifdef ENABLE_AUTO_BED_LEVELING
-    zprobe_zoffset = -Z_PROBE_OFFSET_FROM_EXTRUDER;
+    zprobe_zoffset = Z_PROBE_OFFSET_FROM_EXTRUDER;
   #endif
 
   #ifdef DELTA
@@ -866,12 +866,11 @@ void Config_PrintSettings(bool forReplay) {
         SERIAL_ECHOLNPGM("Z-Probe Offset (mm):");
       }
       CONFIG_ECHO_START;
-      SERIAL_ECHOPAIR("  M", (unsigned long)CUSTOM_M_CODE_SET_Z_PROBE_OFFSET);
-      SERIAL_ECHOPAIR(" Z", -zprobe_zoffset);
+      SERIAL_ECHOPAIR("  M" STRINGIFY(CUSTOM_M_CODE_SET_Z_PROBE_OFFSET), zprobe_zoffset);
     #else
       if (!forReplay) {
         CONFIG_ECHO_START;
-        SERIAL_ECHOPAIR("Z-Probe Offset (mm):", -zprobe_zoffset);
+        SERIAL_ECHOPAIR("Z-Probe Offset (mm):", zprobe_zoffset);
       }
     #endif
     SERIAL_EOL;