marlin/Marlin/UBL_G29.cpp

/**
 * Marlin 3D Printer Firmware
 * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
 *
 * Based on Sprinter and grbl.
 * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include "Marlin.h"
#if ENABLED(AUTO_BED_LEVELING_UBL)
  //#include "vector_3.h"
  //#include "qr_solve.h"

  #include "UBL.h"
  #include "hex_print_routines.h"
  #include "configuration_store.h"
  #include "planner.h"
  #include "ultralcd.h"

  #include <avr/io.h>

  void lcd_babystep_z();
  void lcd_return_to_status();
  bool lcd_clicked();
  void lcd_implementation_clear();
  void lcd_mesh_edit_setup(float inital);
  float lcd_mesh_edit();
  void lcd_z_offset_edit_setup(float);
  float lcd_z_offset_edit();

  extern float meshedit_done;
  extern long babysteps_done;
  extern float code_value_float();
  extern bool code_value_bool();
  extern bool code_has_value();
  extern float probe_pt(float x, float y, bool, int);
  extern float zprobe_zoffset;
  extern bool set_probe_deployed(bool);
  #define DEPLOY_PROBE() set_probe_deployed(true)
  #define STOW_PROBE() set_probe_deployed(false)
  bool ProbeStay = true;
  float ubl_3_point_1_X = UBL_PROBE_PT_1_X;
  float ubl_3_point_1_Y = UBL_PROBE_PT_1_Y;
  float ubl_3_point_2_X = UBL_PROBE_PT_2_X;
  float ubl_3_point_2_Y = UBL_PROBE_PT_2_Y;
  float ubl_3_point_3_X = UBL_PROBE_PT_3_X;
  float ubl_3_point_3_Y = UBL_PROBE_PT_3_Y;

  #define SIZE_OF_LITTLE_RAISE 0
  #define BIG_RAISE_NOT_NEEDED 0
  extern void lcd_quick_feedback();

  /**
   * G29: Unified Bed Leveling by Roxy
   */

  // Transform required to compensate for bed level
  //extern matrix_3x3 plan_bed_level_matrix;

  /**
   *   Get the position applying the bed level matrix
   */

  //vector_3 plan_get_position();

  // static void set_bed_level_equation_lsq(double* plane_equation_coefficients);
  // static void set_bed_level_equation_3pts(float z_at_pt_1, float z_at_pt_2, float z_at_pt_3);

  /**
   *   G29: Mesh Based Compensation System
   *
   *   Parameters understood by this leveling system:
   *
   *   A     Activate  Activate the Unified Bed Leveling system.
   *
   *   B #   Business  Use the 'Business Card' mode of the Manual Probe subsystem.  This is invoked as
   *   G29 P2 B   The mode of G29 P2 allows you to use a bussiness card or recipe card
   *   as a shim that the nozzle will pinch as it is lowered. The idea is that you
   *   can easily feel the nozzle getting to the same height by the amount of resistance
   *   the business card exhibits to movement. You should try to achieve the same amount
   *   of resistance on each probed point to facilitate accurate and repeatable measurements.
   *   You should be very careful not to drive the nozzle into the bussiness card with a
   *   lot of force as it is very possible to cause damage to your printer if your are
   *   careless.  If you use the B option with G29 P2 B you can leave the number parameter off
   *   on its first use to enable measurement of the business card thickness.  Subsequent usage
   *   of the B parameter can have the number previously measured supplied to the command.
   *   Incidently, you are much better off using something like a Spark Gap feeler gauge than
   *   something that compresses like a Business Card.
   *
   *   C     Continue  Continue, Constant, Current Location. This is not a primary command.  C is used to
   *   further refine the behaviour of several other commands.  Issuing a G29 P1 C will
   *   continue the generation of a partially constructed Mesh without invalidating what has
   *   been done.  Issuing a G29 P2 C will tell the Manual Probe subsystem to use the current
   *   location in its search for the closest unmeasured Mesh Point.  When used with a G29 Z C
   *   it indicates to use the current location instead of defaulting to the center of the print bed.
   *
   *   D     Disable   Disable the Unified Bed Leveling system.
   *
   *   E     Stow_probe Stow the probe after each sampled point.
   *
   *   F #   Fade   *   Fade the amount of Mesh Based Compensation over a specified height.  At the specified height,
   *   no correction is applied and natural printer kenimatics take over.  If no number is specified
   *   for the command, 10mm is assummed to be reasonable.
   *
   *   G #   Grid   *   Perform a Grid Based Leveling of the current Mesh using a grid with n points on
   *   a side.
   *
   *   H #   Height    Specify the Height to raise the nozzle after each manual probe of the bed.  The
   *   default is 5mm.
   *
   *   I #   Invalidate Invalidate specified number of Mesh Points.  The nozzle location is used unless
   *   the X and Y parameter are used. If no number is specified, only the closest Mesh
   *   point to the location is invalidated.  The M parameter is available as well to produce
   *   a map after the operation.  This command is useful to invalidate a portion of the
   *   Mesh so it can be adjusted using other tools in the Unified Bed Leveling System.  When
   *   attempting to invalidate an isolated bad point in the mesh, the M option will indicate
   *   where the nozzle is positioned in the Mesh with (#).  You can move the nozzle around on
   *   the bed and use this feature to select the center of the area (or cell) you want to
   *   invalidate.
   *
   *   K #   Kompare   Kompare current Mesh with stored Mesh # replacing current Mesh with the result.  This
   *   command litterly performs a difference between two Mesh.
   *
   *   L     Load   *   Load Mesh from the previously activated location in the EEPROM.
   *
   *   L #   Load   *   Load Mesh from the specified location in the EEPROM.  Set this location as activated
   *   for subsequent Load and Store operations.
   *
   *   O     Map   *    Display the Mesh Map Topology.
   *   The parameter can be specified alone (ie. G29 O) or in combination with many of the
   *   other commands.  The Mesh Map option works with all of the Phase
   *   commands (ie. G29 P4 R 5 X 50 Y100 C -.1 O)
   *
   *   N    No Home    G29 normally insists that a G28 has been performed.  You can over rule this with an
   *   N option.  In general, you should not do this.  This can only be done safely with
   *   commands that do not move the nozzle.
   *
   *   The P or Phase commands are used for the bulk of the work to setup a Mesh.  In general, your Mesh will
   *   start off being initialized with a G29 P0 or a G29 P1. Further refinement of the Mesh happens with
   *   each additional Phase that processes it.
   *
   *   P0    Phase 0   Zero Mesh Data and turn off the Mesh Compensation System.  This reverts the
   *   3D Printer to the same state it was in before the Unified Bed Leveling Compensation
   *   was turned on.  Setting the entire Mesh to Zero is a special case that allows
   *   a subsequent G or T leveling operation for backward compatability.
   *
   *   P1    Phase 1   Invalidate entire Mesh and continue with automatic generation of the Mesh data using
   *   the Z-Probe. Depending upon the values of DELTA_PROBEABLE_RADIUS and
   *   DELTA_PRINTABLE_RADIUS some area of the bed will not have Mesh Data automatically
   *   generated.  This will be handled in Phase 2.  If the Phase 1 command is given the
   *   C (Continue) parameter it does not invalidate the Mesh prior to automatically
   *   probing needed locations.  This allows you to invalidate portions of the Mesh but still
   *   use the automatic probing capabilities of the Unified Bed Leveling System.  An X and Y
   *   parameter can be given to prioritize where the command should be trying to measure points.
   *   If the X and Y parameters are not specified the current probe position is used.  Phase 1
   *   allows you to specify the M (Map) parameter so you can watch the generation of the Mesh.
   *   Phase 1 also watches for the LCD Panel's Encoder Switch being held in a depressed state.
   *   It will suspend generation of the Mesh if it sees the user request that.  (This check is
   *   only done between probe points.  You will need to press and hold the switch until the
   *   Phase 1 command can detect it.)
   *
   *   P2    Phase 2   Probe areas of the Mesh that can not be automatically handled.  Phase 2 respects an H
   *   parameter to control the height between Mesh points.  The default height for movement
   *   between Mesh points is 5mm.  A smaller number can be used to make this part of the
   *   calibration less time consuming.  You will be running the nozzle down until it just barely
   *   touches the glass.  You should have the nozzle clean with no plastic obstructing your view.
   *   Use caution and move slowly.  It is possible to damage your printer if you are careless.
   *   Note that this command will use the configuration #define SIZE_OF_LITTLE_RAISE if the
   *   nozzle is moving a distance of less than BIG_RAISE_NOT_NEEDED.
   *
   *   The H parameter can be set negative if your Mesh dips in a large area.  You can press
   *   and hold the LCD Panel's encoder wheel to terminate the current Phase 2 command.  You
   *   can then re-issue the G29 P 2 command with an H parameter that is more suitable for the
   *   area you are manually probing.  Note that the command tries to start you in a corner
   *   of the bed where movement will be predictable.  You can force the location to be used in
   *   the distance calculations by using the X and Y parameters.  You may find it is helpful to
   *   print out a Mesh Map (G29 O ) to understand where the mesh is invalidated and where
   *   the nozzle will need to move in order to complete the command.   The C parameter is
   *   available on the Phase 2 command also and indicates the search for points to measure should
   *   be done based on the current location of the nozzle.
   *
   *   A B parameter is also available for this command and described up above.  It places the
   *   manual probe subsystem into Business Card mode where the thickness of a business care is
   *   measured and then used to accurately set the nozzle height in all manual probing for the
   *   duration of the command.  (S for Shim mode would be a better parameter name, but S is needed
   *   for Save or Store of the Mesh to EEPROM)  A Business card can be used, but you will have
   *   better results if you use a flexible Shim that does not compress very much.  That makes it
   *   easier for you to get the nozzle to press with similar amounts of force against the shim so you
   *   can get accurate measurements.  As you are starting to touch the nozzle against the shim try
   *   to get it to grasp the shim with the same force as when you measured the thickness of the
   *   shim at the start of the command.
   *
   *   Phase 2 allows the O (Map) parameter to be specified.  This helps the user see the progression
   *   of the Mesh being built.
   *
   *   P3    Phase 3   Fill the unpopulated regions of the Mesh with a fixed value.  The C parameter is used to
   *   specify the Constant value to fill all invalid areas of the Mesh.  If no C parameter is
   *   specified, a value of 0.0 is assumed.  The R parameter can be given to specify the number
   *   of points to set.  If the R parameter is specified the current nozzle position is used to
   *   find the closest points to alter unless the X and Y parameter are used to specify the fill
   *   location.
   *
   *   P4    Phase 4   Fine tune the Mesh.  The Delta Mesh Compensation System assume the existance of
   *   an LCD Panel.  It is possible to fine tune the mesh without the use of an LCD Panel.
   *   (More work and details on doing this later!)
   *   The System will search for the closest Mesh Point to the nozzle.  It will move the
   *   nozzle to this location.  The user can use the LCD Panel to carefully adjust the nozzle
   *   so it is just barely touching the bed.  When the user clicks the control, the System
   *   will lock in that height for that point in the Mesh Compensation System.
   *
   *   Phase 4 has several additional parameters that the user may find helpful.  Phase 4
   *   can be started at a specific location by specifying an X and Y parameter.  Phase 4
   *   can be requested to continue the adjustment of Mesh Points by using the R(epeat)
   *   parameter.  If the Repetition count is not specified, it is assumed the user wishes
   *   to adjust the entire matrix.  The nozzle is moved to the Mesh Point being edited.
   *   The command can be terminated early (or after the area of interest has been edited) by
   *   pressing and holding the encoder wheel until the system recognizes the exit request.
   *   Phase 4's general form is G29 P4 [R # of points] [X position] [Y position]
   *
   *   Phase 4 is intended to be used with the G26 Mesh Validation Command.  Using the
   *   information left on the printer's bed from the G26 command it is very straight forward
   *   and easy to fine tune the Mesh.  One concept that is important to remember and that
   *   will make using the Phase 4 command easy to use is this:  You are editing the Mesh Points.
   *   If you have too little clearance and not much plastic was extruded in an area, you want to
   *   LOWER the Mesh Point at the location.  If you did not get good adheasion, you want to
   *   RAISE the Mesh Point at that location.
   *
   *
   *   P5    Phase 5   Find Mean Mesh Height and Standard Deviation.  Typically, it is easier to use and
   *   work with the Mesh if it is Mean Adjusted.  You can specify a C parameter to
   *   Correct the Mesh to a 0.00 Mean Height.  Adding a C parameter will automatically
   *   execute a G29 P6 C <mean height>.
   *
   *   P6    Phase 6   Shift Mesh height.  The entire Mesh's height is adjusted by the height specified
   *   with the C parameter.  Being able to adjust the height of a Mesh is useful tool.  It
   *   can be used to compensate for poorly calibrated Z-Probes and other errors.  Ideally,
   *   you should have the Mesh adjusted for a Mean Height of 0.00 and the Z-Probe measuring
   *   0.000 at the Z Home location.
   *
   *   Q     Test   *   Load specified Test Pattern to assist in checking correct operation of system.  This
   *   command is not anticipated to be of much value to the typical user.  It is intended
   *   for developers to help them verify correct operation of the Unified Bed Leveling System.
   *
   *   S     Store     Store the current Mesh in the Activated area of the EEPROM.  It will also store the
   *   current state of the Unified Bed Leveling system in the EEPROM.
   *
   *   S #   Store     Store the current Mesh at the specified location in EEPROM.  Activate this location
   *   for subsequent Load and Store operations.  It will also store the current state of
   *   the Unified Bed Leveling system in the EEPROM.
   *
   *   S -1  Store     Store the current Mesh as a print out that is suitable to be feed back into
   *   the system at a later date. The text generated can be saved and later sent by PronterFace or
   *   Repetier Host to reconstruct the current mesh on another machine.
   *
   *   T     3-Point   Perform a 3 Point Bed Leveling on the current Mesh
   *
   *   W     What?     Display valuable data the Unified Bed Leveling System knows.
   *
   *   X #   *      *    Specify X Location for this line of commands
   *
   *   Y #   *      *    Specify Y Location for this line of commands
   *
   *   Z     Zero   *   Probes to set the Z Height of the nozzle.  The entire Mesh can be raised or lowered
   *   by just doing a G29 Z
   *
   *   Z #   Zero   *   The entire Mesh can be raised or lowered to conform with the specified difference.
   *   zprobe_zoffset is added to the calculation.
   *
   *
   *   Release Notes:
   *   You MUST do a M502 & M500 pair of commands to initialize the storage.  Failure to do this
   *   will cause all kinds of problems.  Enabling EEPROM Storage is highly recommended.  With
   *   EEPROM Storage of the mesh, you are limited to 3-Point and Grid Leveling.  (G29 P0 T and
   *   G29 P0 G respectively.)
   *
   *   Z-Probe Sleds are not currently fully supported.  There were too many complications caused
   *   by them to support them in the Unified Bed Leveling code.  Support for them will be handled
   *   better in the upcoming Z-Probe Object that will happen during the Code Clean Up phase.  (That
   *   is what they really are:  A special case of the Z-Probe.)  When a Z-Probe Object appears, it
   *   should slip in under the Unified Bed Leveling code without major trauma.
   *
   *   When you do a G28 and then a G29 P1 to automatically build your first mesh, you are going to notice
   *   the Unified Bed Leveling probes points further and further away from the starting location. (The
   *   starting location defaults to the center of the bed.)   The original Grid and Mesh leveling used
   *   a Zig Zag pattern. The new pattern is better, especially for people with Delta printers.  This
   *   allows you to get the center area of the Mesh populated (and edited) quicker.  This allows you to
   *   perform a small print and check out your settings quicker.  You do not need to populate the
   *   entire mesh to use it.  (You don't want to spend a lot of time generating a mesh only to realize
   *   you don't have the resolution or zprobe_zoffset set correctly.  The Mesh generation
   *   gathers points closest to where the nozzle is located unless you specify an (X,Y) coordinate pair.
   *
   *   The Unified Bed Leveling uses a lot of EEPROM storage to hold its data.  And it takes some effort
   *   to get this Mesh data correct for a user's printer.  We do not want this data destroyed as
   *   new versions of Marlin add or subtract to the items stored in EEPROM.  So, for the benefit of
   *   the users, we store the Mesh data at the end of the EEPROM and do not keep it contiguous with the
   *   other data stored in the EEPROM.  (For sure the developers are going to complain about this, but
   *   this is going to be helpful to the users!)
   *
   *   The foundation of this Bed Leveling System is built on Epatel's Mesh Bed Leveling code.  A big
   *   'Thanks!' to him and the creators of 3-Point and Grid Based leveling.  Combining thier contributions
   *   we now have the functionality and features of all three systems combined.
   */

  int Unified_Bed_Leveling_EEPROM_start = -1;
  int UBL_has_control_of_LCD_Panel = 0;
  volatile int G29_encoderDiff = 0; // This is volatile because it is getting changed at interrupt time.

  // We keep the simple parameter flags and values as 'static' because we break out the
  // parameter parsing into a support routine.

  static int G29_Verbose_Level = 0, Test_Value = 0,
             Phase_Value = -1, Repetition_Cnt = 1;
  static bool Repeat_Flag = UBL_OK, C_Flag = false, X_Flag = UBL_OK, Y_Flag = UBL_OK, Statistics_Flag = UBL_OK, Business_Card_Mode = false;
  static float X_Pos = 0.0, Y_Pos = 0.0, Height_Value = 5.0, measured_z, card_thickness = 0.0, Constant = 0.0;
  static int Storage_Slot = 0, Test_Pattern = 0;

  #if ENABLED(ULTRA_LCD)
    void lcd_setstatus(const char* message, bool persist);
  #endif

  void gcode_G29() {
    mesh_index_pair location;
    int i, j, k;
    float Z1, Z2, Z3;

    G29_Verbose_Level = 0;  // These may change, but let's get some reasonable values into them.
    Repeat_Flag       = UBL_OK;
    Repetition_Cnt    = 1;
    C_Flag            = false;

    SERIAL_PROTOCOLPGM("Unified_Bed_Leveling_EEPROM_start=");
    SERIAL_PROTOCOLLN(Unified_Bed_Leveling_EEPROM_start);

    if (Unified_Bed_Leveling_EEPROM_start < 0) {
      SERIAL_PROTOCOLLNPGM("?You need to enable your EEPROM and initialize it ");
      SERIAL_PROTOCOLLNPGM("with M502, M500, M501 in that order.\n");
      return;
    }

    if (!code_seen('N') && axis_unhomed_error(true, true, true))  // Don't allow auto-leveling without homing first
      gcode_G28();

    if (G29_Parameter_Parsing()) return; // abort if parsing the simple parameters causes a problem,

    // Invalidate Mesh Points. This command is a little bit asymetrical because
    // it directly specifies the repetition count and does not use the 'R' parameter.
    if (code_seen('I')) {
      Repetition_Cnt = code_has_value() ? code_value_int() : 1;
      while (Repetition_Cnt--) {
        location = find_closest_mesh_point_of_type(REAL, X_Pos, Y_Pos, 0, NULL);  // The '0' says we want to use the nozzle's position
        if (location.x_index < 0) {
          SERIAL_PROTOCOLLNPGM("Entire Mesh invalidated.\n");
          break;            // No more invalid Mesh Points to populate
        }
        z_values[location.x_index][location.y_index] = NAN;
      }
      SERIAL_PROTOCOLLNPGM("Locations invalidated.\n");
    }

    if (code_seen('Q')) {

      if (code_has_value()) Test_Pattern = code_value_int();

      if (Test_Pattern < 0 || Test_Pattern > 4) {
        SERIAL_PROTOCOLLNPGM("Invalid Test_Pattern value. (0-4)\n");
        return;
      }
      SERIAL_PROTOCOLLNPGM("Loading Test_Pattern values.\n");
      switch (Test_Pattern) {
        case 0:
          for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++) {         // Create a bowl shape. This is
            for (j = 0; j < UBL_MESH_NUM_Y_POINTS; j++) {       // similar to what a user would see with
              Z1 = 0.5 * (UBL_MESH_NUM_X_POINTS) - i;  // a poorly calibrated Delta.
              Z2 = 0.5 * (UBL_MESH_NUM_Y_POINTS) - j;
              z_values[i][j] += 2.0 * HYPOT(Z1, Z2);
            }
          }
        break;
        case 1:
          for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++) {         // Create a diagonal line several Mesh
            z_values[i][i] += 9.999;                             // cells thick that is raised
            if (i < UBL_MESH_NUM_Y_POINTS - 1)
              z_values[i][i + 1] += 9.999;                       // We want the altered line several mesh points thick
            if (i > 0)
              z_values[i][i - 1] += 9.999;                       // We want the altered line several mesh points thick
          }
          break;
        case 2:
          // Allow the user to specify the height because 10mm is
          // a little bit extreme in some cases.
          for (i = (UBL_MESH_NUM_X_POINTS) / 3.0; i < 2 * ((UBL_MESH_NUM_X_POINTS) / 3.0); i++)   // Create a rectangular raised area in
            for (j = (UBL_MESH_NUM_Y_POINTS) / 3.0; j < 2 * ((UBL_MESH_NUM_Y_POINTS) / 3.0); j++) // the center of the bed
              z_values[i][j] += code_seen('C') ? Constant : 9.99;
          break;
        case 3:
          break;
      }
    }

    if (code_seen('P')) {
      Phase_Value = code_value_int();
      if (Phase_Value < 0 || Phase_Value > 7) {
        SERIAL_PROTOCOLLNPGM("Invalid Phase value. (0-4)\n");
        return;
      }
      switch (Phase_Value) {
        //
        // Zero Mesh Data
        //
        case 0:
          blm.reset();
          SERIAL_PROTOCOLLNPGM("Mesh zeroed.\n");
          break;
        //
        // Invalidate Entire Mesh and Automatically Probe Mesh in areas that can be reached by the probe
        //
        case 1:
          if (!code_seen('C') )  {
            blm.invalidate();
            SERIAL_PROTOCOLLNPGM("Mesh invalidated. Probing mesh.\n");
          }
          if (G29_Verbose_Level > 1) {
            SERIAL_ECHOPGM("Probing Mesh Points Closest to (");
            SERIAL_ECHO(X_Pos);
            SERIAL_ECHOPAIR(",", Y_Pos);
            SERIAL_PROTOCOLLNPGM(")\n");
          }
          probe_entire_mesh( X_Pos+X_PROBE_OFFSET_FROM_EXTRUDER, Y_Pos+Y_PROBE_OFFSET_FROM_EXTRUDER,
                             code_seen('O') || code_seen('M'), code_seen('E'));
          break;
        //
        // Manually Probe Mesh in areas that can not be reached by the probe
        //
        case 2:
          SERIAL_PROTOCOLLNPGM("Manually probing unreachable mesh locations.\n");
          do_blocking_move_to_z(Z_CLEARANCE_BETWEEN_PROBES);
          if (!X_Flag && !Y_Flag) {      // use a good default location for the path
            X_Pos = X_MIN_POS;
            Y_Pos = Y_MIN_POS;
            if (X_PROBE_OFFSET_FROM_EXTRUDER > 0)   // The flipped > and < operators on these two comparisons is
              X_Pos = X_MAX_POS;                    // intentional. It should cause the probed points to follow a

            if (Y_PROBE_OFFSET_FROM_EXTRUDER < 0)   // nice path on Cartesian printers. It may make sense to
              Y_Pos = Y_MAX_POS;                    // have Delta printers default to the center of the bed.

          }           // For now, until that is decided, it can be forced with the X
                      // and Y parameters.
          if (code_seen('C')) {
            X_Pos = current_position[X_AXIS];
            Y_Pos = current_position[Y_AXIS];
          }

          Height_Value = code_seen('H') && code_has_value() ? code_value_float() : Z_CLEARANCE_BETWEEN_PROBES;

          if ((Business_Card_Mode = code_seen('B'))) {
            card_thickness = code_has_value() ? code_value_float() : measure_business_card_thickness(Height_Value);

            if (fabs(card_thickness) > 1.5)  {
              SERIAL_PROTOCOLLNPGM("?Error in Business Card measurment.\n");
              return;
            }
          }
          manually_probe_remaining_mesh( X_Pos, Y_Pos, Height_Value, card_thickness, code_seen('O') || code_seen('M'));
          break;
        //
        // Populate invalid Mesh areas with a constant
        //
        case 3:
          Height_Value = 0.0; // Assume 0.0 until proven otherwise
          if (code_seen('C')) Height_Value = Constant;
          // If no repetition is specified, do the whole Mesh
          if (!Repeat_Flag) Repetition_Cnt = 9999;
          while (Repetition_Cnt--) {
            location = find_closest_mesh_point_of_type( INVALID, X_Pos, Y_Pos, 0, NULL); // The '0' says we want to use the nozzle's position
            if (location.x_index < 0) break; // No more invalid Mesh Points to populate
            z_values[location.x_index][location.y_index] = Height_Value;
          }
          break;
        //
        // Fine Tune (Or Edit) the Mesh
        //
        case 4:
          fine_tune_mesh(X_Pos, Y_Pos, Height_Value, code_seen('O') || code_seen('M'));
          break;
        case 5:
          Find_Mean_Mesh_Height();
          break;
        case 6:
          Shift_Mesh_Height();
          break;

        case 10:
          UBL_has_control_of_LCD_Panel++;     // Debug code... Pan no attention to this stuff
          SERIAL_ECHO_START;
          SERIAL_ECHOPGM("Checking G29 has control of LCD Panel:\n");
          while(!G29_lcd_clicked()) {
            idle();
            delay(250);
            SERIAL_PROTOCOL(G29_encoderDiff);
            G29_encoderDiff = 0;
            SERIAL_EOL;
          }
          while (G29_lcd_clicked()) idle();
          UBL_has_control_of_LCD_Panel = 0;;
          SERIAL_ECHOPGM("G29 giving back control of LCD Panel.\n");
          break;
      }
    }

    if (code_seen('T')) {
      Z1 = probe_pt(ubl_3_point_1_X, ubl_3_point_1_Y, false /*Stow Flag*/, G29_Verbose_Level) + zprobe_zoffset;
      Z2 = probe_pt(ubl_3_point_2_X, ubl_3_point_2_Y, false /*Stow Flag*/, G29_Verbose_Level) + zprobe_zoffset;
      Z3 = probe_pt(ubl_3_point_3_X, ubl_3_point_3_Y, true  /*Stow Flag*/, G29_Verbose_Level) + zprobe_zoffset;

      //  We need to adjust Z1, Z2, Z3 by the Mesh Height at these points. Just because they are non-zero doesn't mean
      //  the Mesh is tilted!  (We need to compensate each probe point by what the Mesh says that location's height is)

      Z1 -= blm.get_z_correction(ubl_3_point_1_X, ubl_3_point_1_Y);
      Z2 -= blm.get_z_correction(ubl_3_point_2_X, ubl_3_point_2_Y);
      Z3 -= blm.get_z_correction(ubl_3_point_3_X, ubl_3_point_3_Y);

      do_blocking_move_to_xy((X_MAX_POS - (X_MIN_POS)) / 2.0, (Y_MAX_POS - (Y_MIN_POS)) / 2.0);
      tilt_mesh_based_on_3pts(Z1, Z2, Z3);
    }

    //
    // Much of the 'What?' command can be eliminated. But until we are fully debugged, it is
    // good to have the extra information. Soon... we prune this to just a few items
    //
    if (code_seen('W')) G29_What_Command();

    //
    // When we are fully debugged, the EEPROM dump command will get deleted also. But
    // right now, it is good to have the extra information. Soon... we prune this.
    //
    if (code_seen('J')) G29_EEPROM_Dump();   // EEPROM Dump

    //
    // When we are fully debugged, this may go away. But there are some valid
    // use cases for the users. So we can wait and see what to do with it.
    //

    if (code_seen('K')) // Kompare Current Mesh Data to Specified Stored Mesh
      G29_Kompare_Current_Mesh_to_Stored_Mesh();

    //
    // Load a Mesh from the EEPROM
    //

    if (code_seen('L')) {     // Load Current Mesh Data
      Storage_Slot = code_has_value() ? code_value_int() : blm.state.EEPROM_storage_slot;

      k = E2END - sizeof(blm.state);
      j = (k - Unified_Bed_Leveling_EEPROM_start) / sizeof(z_values);

      if (Storage_Slot < 0 || Storage_Slot >= j || Unified_Bed_Leveling_EEPROM_start <= 0) {
        SERIAL_PROTOCOLLNPGM("?EEPROM storage not available for use.\n");
        return;
      }
      blm.load_mesh(Storage_Slot);
      blm.state.EEPROM_storage_slot = Storage_Slot;
      if (Storage_Slot != blm.state.EEPROM_storage_slot)
        blm.store_state();
      SERIAL_PROTOCOLLNPGM("Done.\n");
    }

    //
    // Store a Mesh in the EEPROM
    //

    if (code_seen('S')) {     // Store (or Save) Current Mesh Data
      Storage_Slot = code_has_value() ? code_value_int() : blm.state.EEPROM_storage_slot;

      if (Storage_Slot == -1) {                     // Special case, we are going to 'Export' the mesh to the
        SERIAL_ECHOPGM("G29 I 999\n");                // host in a form it can be reconstructed on a different machine
        for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++) {
          for (j = 0;  j < UBL_MESH_NUM_Y_POINTS; j++) {
            if (!isnan(z_values[i][j])) {
              SERIAL_ECHOPAIR("M421 I ", i);
              SERIAL_ECHOPAIR(" J ", j);
              SERIAL_ECHOPGM(" Z ");
              SERIAL_PROTOCOL_F(z_values[i][j], 6);
              SERIAL_EOL;
            }
          }
        }
        return;
      }

      int k = E2END - sizeof(blm.state),
          j = (k - Unified_Bed_Leveling_EEPROM_start) / sizeof(z_values);

      if (Storage_Slot < 0 || Storage_Slot >= j || Unified_Bed_Leveling_EEPROM_start <= 0) {
        SERIAL_PROTOCOLLNPGM("?EEPROM storage not available for use.\n");
        SERIAL_PROTOCOLLNPAIR("?Use 0 to ", j - 1);
        goto LEAVE;
      }
      blm.store_mesh(Storage_Slot);
      blm.state.EEPROM_storage_slot = Storage_Slot;
      //
      //  if (Storage_Slot != blm.state.EEPROM_storage_slot)
      blm.store_state();    // Always save an updated copy of the UBL State info

      SERIAL_PROTOCOLLNPGM("Done.\n");
    }

    if (code_seen('O') || code_seen('M')) {
      i = code_has_value() ? code_value_int() : 0;
      blm.display_map(i);
    }

    if (code_seen('Z')) {
      if (code_has_value()) {
        blm.state.z_offset = code_value_float();   // do the simple case. Just lock in the specified value
      }
      else {
        save_UBL_active_state_and_disable();
        //measured_z = probe_pt(X_Pos + X_PROBE_OFFSET_FROM_EXTRUDER, Y_Pos+Y_PROBE_OFFSET_FROM_EXTRUDER, ProbeDeployAndStow, G29_Verbose_Level);

        measured_z = 1.5;
        do_blocking_move_to_z(measured_z);  // Get close to the bed, but leave some space so we don't damage anything
                                            // The user is not going to be locking in a new Z-Offset very often so
                                            // it won't be that painful to spin the Encoder Wheel for 1.5mm
        lcd_implementation_clear();
        lcd_z_offset_edit_setup(measured_z);
        do {
          measured_z = lcd_z_offset_edit();
          idle();
          do_blocking_move_to_z(measured_z);
        } while (!G29_lcd_clicked());

        UBL_has_control_of_LCD_Panel = 1; // There is a race condition for the Encoder Wheel getting clicked.
                                          // It could get detected in lcd_mesh_edit (actually _lcd_mesh_fine_tune( )
                                          // or here. So, until we are done looking for a long Encoder Wheel Press,
                                          // we need to take control of the panel
        millis_t nxt = millis() + 1500UL;
        lcd_return_to_status();
        while (G29_lcd_clicked()) { // debounce and watch for abort
          idle();
          if (ELAPSED(millis(), nxt)) {
            SERIAL_PROTOCOLLNPGM("\nZ-Offset Adjustment Stopped.");
            do_blocking_move_to_z(Z_CLEARANCE_DEPLOY_PROBE);
            lcd_setstatus("Z-Offset Stopped", true);

            while (G29_lcd_clicked()) idle();

            UBL_has_control_of_LCD_Panel = 0;
            restore_UBL_active_state_and_leave();
            goto LEAVE;
          }
        }
        UBL_has_control_of_LCD_Panel = 0;
        delay(20); // We don't want any switch noise.

        blm.state.z_offset = measured_z;

        lcd_implementation_clear();
        restore_UBL_active_state_and_leave();
      }
    }

    LEAVE:
    #if ENABLED(ULTRA_LCD)
      lcd_setstatus("                         ", true);
      lcd_quick_feedback();
    #endif
    UBL_has_control_of_LCD_Panel = 0;
  }

  void Find_Mean_Mesh_Height()  {
    int i, j, n;
    float sum, sum_of_diff_squared, sigma, difference, mean;

    sum = sum_of_diff_squared = 0.0;
    n = 0;
    for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++) {
      for (j = 0; j < UBL_MESH_NUM_Y_POINTS; j++) {
        if (!isnan(z_values[i][j])) {
          sum += z_values[i][j];
          n++;
        }
      }
    }
    mean = sum / n;
    //
    // Now do the sumation of the squares of difference from mean
    //
    for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++) {
      for (j = 0;  j < UBL_MESH_NUM_Y_POINTS; j++) {
        if (!isnan(z_values[i][j])) {
          difference = (z_values[i][j] - mean);
          sum_of_diff_squared += difference * difference;
        }
      }
    }
    SERIAL_ECHOLNPAIR("# of samples: ", n);
    SERIAL_ECHOPGM("Mean Mesh Height: ");
    SERIAL_PROTOCOL_F(mean, 6);
    SERIAL_EOL;

    sigma = sqrt( sum_of_diff_squared / (n + 1));
    SERIAL_ECHOPGM("Standard Deviation: ");
    SERIAL_PROTOCOL_F(sigma, 6);
    SERIAL_EOL;

    if (C_Flag)
      for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++)
        for (j = 0;  j < UBL_MESH_NUM_Y_POINTS; j++)
          if (!isnan(z_values[i][j]))
            z_values[i][j] -= mean + Constant;
  }

  void Shift_Mesh_Height( )  {
    for (uint8_t i = 0; i < UBL_MESH_NUM_X_POINTS; i++)
      for (uint8_t j = 0;  j < UBL_MESH_NUM_Y_POINTS; j++)
        if (!isnan(z_values[i][j]))
          z_values[i][j] += Constant;
  }

  // probe_entire_mesh(X_Pos, Y_Pos)  probes all invalidated locations of the mesh that can be reached
  // by the probe. It attempts to fill in locations closest to the nozzle's start location first.

  void probe_entire_mesh(float X_Pos, float Y_Pos, bool do_UBL_MESH_Map, bool stow_probe)  {
    mesh_index_pair location;
    float xProbe, yProbe, measured_z;

    UBL_has_control_of_LCD_Panel++;
    save_UBL_active_state_and_disable();   // we don't do bed level correction because we want the raw data when we probe
    DEPLOY_PROBE();

    do {
      if (G29_lcd_clicked()) {
        SERIAL_PROTOCOLLNPGM("\nMesh only partially populated.");
        lcd_quick_feedback();
        while (G29_lcd_clicked()) idle();
        UBL_has_control_of_LCD_Panel = 0;
        STOW_PROBE();
        restore_UBL_active_state_and_leave();
        return;
      }
      location = find_closest_mesh_point_of_type( INVALID, X_Pos,  Y_Pos, 1, NULL);  // the '1' says we want the location to be relative to the probe
      if (location.x_index>=0 && location.y_index>=0) {
        xProbe = blm.map_x_index_to_bed_location(location.x_index);
        yProbe = blm.map_y_index_to_bed_location(location.y_index);
        if (xProbe < MIN_PROBE_X || xProbe > MAX_PROBE_X || yProbe < MIN_PROBE_Y || yProbe > MAX_PROBE_Y) {
          SERIAL_PROTOCOLLNPGM("?Error: Attempt to probe off the bed.");
          UBL_has_control_of_LCD_Panel = 0;
          goto LEAVE;
        }
        measured_z = probe_pt(xProbe, yProbe, stow_probe, G29_Verbose_Level);
        z_values[location.x_index][location.y_index] = measured_z + Z_PROBE_OFFSET_FROM_EXTRUDER;
      }

      if (do_UBL_MESH_Map) blm.display_map(1);
    } while (location.x_index >= 0 && location.y_index >= 0);

    LEAVE:
    STOW_PROBE();
    restore_UBL_active_state_and_leave();

    X_Pos = constrain( X_Pos-X_PROBE_OFFSET_FROM_EXTRUDER, X_MIN_POS, X_MAX_POS);
    Y_Pos = constrain( Y_Pos-Y_PROBE_OFFSET_FROM_EXTRUDER, Y_MIN_POS, Y_MAX_POS);

    do_blocking_move_to_xy(X_Pos, Y_Pos);
  }

  struct vector tilt_mesh_based_on_3pts(float pt1, float pt2, float pt3) {
    struct vector v1, v2, normal;
    float c, d, t;
    int i, j;

    v1.dx = (ubl_3_point_1_X - ubl_3_point_2_X);
    v1.dy = (ubl_3_point_1_Y - ubl_3_point_2_Y);
    v1.dz = (pt1 - pt2);

    v2.dx = (ubl_3_point_3_X - ubl_3_point_2_X);
    v2.dy = (ubl_3_point_3_Y - ubl_3_point_2_Y);
    v2.dz = (pt3 - pt2);

    // do cross product

    normal.dx = v1.dy * v2.dz - v1.dz * v2.dy;
    normal.dy = v1.dz * v2.dx - v1.dx * v2.dz;
    normal.dz = v1.dx * v2.dy - v1.dy * v2.dx;

    // printf("[%f,%f,%f]    ", normal.dx, normal.dy, normal.dz);

    normal.dx /= normal.dz; // This code does two things. This vector is normal to the tilted plane.
    normal.dy /= normal.dz; // However, we don't know its direction. We need it to point up. So if
    normal.dz /= normal.dz; // Z is negative, we need to invert the sign of all components of the vector
    // We also need Z to be unity because we are going to be treating this triangle
    // as the sin() and cos() of the bed's tilt

    //
    // All of 3 of these points should give us the same d constant
    //
    t = normal.dx * ubl_3_point_1_X + normal.dy * ubl_3_point_1_Y;
    d = t + normal.dz * pt1;
    c = d - t;
    SERIAL_ECHOPGM("d from 1st point: ");
    SERIAL_PROTOCOL_F(d, 6);
    SERIAL_ECHOPGM("  c: ");
    SERIAL_PROTOCOL_F(c, 6);
    SERIAL_EOL;
    t = normal.dx * ubl_3_point_2_X + normal.dy * ubl_3_point_2_Y;
    d = t + normal.dz * pt2;
    c = d - t;
    SERIAL_ECHOPGM("d from 2nd point: ");
    SERIAL_PROTOCOL_F(d, 6);
    SERIAL_ECHOPGM("  c: ");
    SERIAL_PROTOCOL_F(c, 6);
    SERIAL_EOL;
    t = normal.dx * ubl_3_point_3_X + normal.dy * ubl_3_point_3_Y;
    d = t + normal.dz * pt3;
    c = d - t;
    SERIAL_ECHOPGM("d from 3rd point: ");
    SERIAL_PROTOCOL_F(d, 6);
    SERIAL_ECHOPGM("  c: ");
    SERIAL_PROTOCOL_F(c, 6);
    SERIAL_EOL;

    for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++) {
      for (j = 0; j < UBL_MESH_NUM_Y_POINTS; j++) {
        c = -((normal.dx * (UBL_MESH_MIN_X + i * (MESH_X_DIST)) + normal.dy * (UBL_MESH_MIN_Y + j * (MESH_Y_DIST))) - d);
        z_values[i][j] += c;
      }
    }
    return normal;
  }

  float use_encoder_wheel_to_measure_point() {
    UBL_has_control_of_LCD_Panel++;
    while (!G29_lcd_clicked()) {     // we need the loop to move the nozzle based on the encoder wheel here!
      idle();
      if (G29_encoderDiff != 0) {
        float new_z;
        // We define a new variable so we can know ahead of time where we are trying to go.
        // The reason is we want G29_encoderDiff cleared so an interrupt can update it even before the move
        // is complete. (So the dial feels responsive to user)
        new_z = current_position[Z_AXIS] + 0.01 * float(G29_encoderDiff);
        G29_encoderDiff = 0;
        do_blocking_move_to_z(new_z);
      }
    }
    while (G29_lcd_clicked()) idle(); // debounce and wait
    UBL_has_control_of_LCD_Panel--;
    return current_position[Z_AXIS];
  }

  float measure_business_card_thickness(float Height_Value) {
    float Z1, Z2;

    UBL_has_control_of_LCD_Panel++;
    save_UBL_active_state_and_disable();   // we don't do bed level correction because we want the raw data when we probe

    SERIAL_PROTOCOLLNPGM("Place Shim Under Nozzle and Perform Measurement.");
    do_blocking_move_to_z(Height_Value);
    do_blocking_move_to_xy((float(X_MAX_POS) - float(X_MIN_POS)) / 2.0, (float(Y_MAX_POS) - float(Y_MIN_POS)) / 2.0);
      //, min( planner.max_feedrate_mm_s[X_AXIS], planner.max_feedrate_mm_s[Y_AXIS])/2.0);

    Z1 = use_encoder_wheel_to_measure_point();
    do_blocking_move_to_z(current_position[Z_AXIS] + SIZE_OF_LITTLE_RAISE);
    UBL_has_control_of_LCD_Panel = 0;

    SERIAL_PROTOCOLLNPGM("Remove Shim and Measure Bed Height.");
    Z2 = use_encoder_wheel_to_measure_point();
    do_blocking_move_to_z(current_position[Z_AXIS] + SIZE_OF_LITTLE_RAISE);

    if (G29_Verbose_Level > 1) {
      SERIAL_ECHOPGM("Business Card is: ");
      SERIAL_PROTOCOL_F(abs(Z1 - Z2), 6);
      SERIAL_PROTOCOLLNPGM("mm thick.");
    }
    restore_UBL_active_state_and_leave();
    return abs(Z1 - Z2);
  }

  void manually_probe_remaining_mesh(float X_Pos, float Y_Pos, float z_clearance, float card_thickness, bool do_UBL_MESH_Map) {
    mesh_index_pair location;
    float last_x, last_y, dx, dy,
          xProbe, yProbe;
    unsigned long cnt;

    UBL_has_control_of_LCD_Panel++;
    last_x = last_y = -9999.99;
    save_UBL_active_state_and_disable();   // we don't do bed level correction because we want the raw data when we probe
    do_blocking_move_to_z(z_clearance);
    do_blocking_move_to_xy(X_Pos, Y_Pos);

    do {
      if (do_UBL_MESH_Map) blm.display_map(1);

      location = find_closest_mesh_point_of_type(INVALID, X_Pos, Y_Pos, 0, NULL); // The '0' says we want to use the nozzle's position
      // It doesn't matter if the probe can not reach the
      // NAN location. This is a manual probe.
      if (location.x_index < 0 && location.y_index < 0) continue;

      xProbe = blm.map_x_index_to_bed_location(location.x_index);
      yProbe = blm.map_y_index_to_bed_location(location.y_index);
      if (xProbe < (X_MIN_POS) || xProbe > (X_MAX_POS) || yProbe < (Y_MIN_POS) || yProbe > (Y_MAX_POS))  {
        SERIAL_PROTOCOLLNPGM("?Error: Attempt to probe off the bed.");
        UBL_has_control_of_LCD_Panel = 0;
        goto LEAVE;
      }

      dx = xProbe - last_x;
      dy = yProbe - last_y;

      if (HYPOT(dx, dy) < BIG_RAISE_NOT_NEEDED)
        do_blocking_move_to_z(current_position[Z_AXIS] + SIZE_OF_LITTLE_RAISE);
      else
        do_blocking_move_to_z(z_clearance);

      last_x = xProbe;
      last_y = yProbe;
      do_blocking_move_to_xy(xProbe, yProbe);

      while (!G29_lcd_clicked()) {     // we need the loop to move the nozzle based on the encoder wheel here!
        idle();
        if (G29_encoderDiff) {
          float new_z;
          // We define a new variable so we can know ahead of time where we are trying to go.
          // The reason is we want G29_encoderDiff cleared so an interrupt can update it even before the move
          // is complete. (So the dial feels responsive to user)
          new_z = current_position[Z_AXIS] + float(G29_encoderDiff) / 100.0;
          G29_encoderDiff = 0;
          do_blocking_move_to_z(new_z);
        }
      }

      cnt = millis();
      while (G29_lcd_clicked()) {     // debounce and watch for abort
        idle();
        if (millis() - cnt > 1500L) {
          SERIAL_PROTOCOLLNPGM("\nMesh only partially populated.");
          do_blocking_move_to_z(Z_CLEARANCE_DEPLOY_PROBE);
          lcd_quick_feedback();
          while (G29_lcd_clicked()) idle();
          UBL_has_control_of_LCD_Panel = 0;
          restore_UBL_active_state_and_leave();
          return;
        }
      }

      z_values[location.x_index][location.y_index] = current_position[Z_AXIS] - card_thickness;
      if (G29_Verbose_Level > 2) {
        SERIAL_PROTOCOL("Mesh Point Measured at: ");
        SERIAL_PROTOCOL_F(z_values[location.x_index][location.y_index], 6);
        SERIAL_EOL;
      }
    } while (location.x_index >= 0 && location.y_index >= 0);

    if (do_UBL_MESH_Map) blm.display_map(1);

    LEAVE:
    restore_UBL_active_state_and_leave();
    do_blocking_move_to_z(Z_CLEARANCE_DEPLOY_PROBE);
    do_blocking_move_to_xy(X_Pos, Y_Pos);
  }

  bool G29_Parameter_Parsing() {

    #if ENABLED(ULTRA_LCD)
      lcd_setstatus("Doing G29 UBL !", true);
      lcd_quick_feedback();
    #endif

    X_Pos = current_position[X_AXIS];
    Y_Pos = current_position[Y_AXIS];
    X_Flag = Y_Flag = Repeat_Flag = UBL_OK;
    Constant = 0.0;
    Repetition_Cnt = 1;

    if ((X_Flag = code_seen('X'))) {
      X_Pos = code_value_float();
      if (X_Pos < X_MIN_POS || X_Pos > X_MAX_POS) {
        SERIAL_PROTOCOLLNPGM("Invalid X location specified.\n");
        return UBL_ERR;
      }
    }

    if ((Y_Flag = code_seen('Y'))) {
      Y_Pos = code_value_float();
      if (Y_Pos < Y_MIN_POS || Y_Pos > Y_MAX_POS) {
        SERIAL_PROTOCOLLNPGM("Invalid Y location specified.\n");
        return UBL_ERR;
      }
    }

    if (X_Flag != Y_Flag) {
      SERIAL_PROTOCOLLNPGM("Both X & Y locations must be specified.\n");
      return UBL_ERR;
    }

    G29_Verbose_Level = 0;
    if (code_seen('V')) {
      G29_Verbose_Level = code_value_int();
      if (G29_Verbose_Level < 0 || G29_Verbose_Level > 4) {
        SERIAL_PROTOCOLLNPGM("Invalid Verbose Level specified. (0-4)\n");
        return UBL_ERR;
      }
    }

    if (code_seen('A')) {     // Activate the Unified Bed Leveling System
      blm.state.active = 1;
      SERIAL_PROTOCOLLNPGM("Unified Bed Leveling System activated.\n");
      blm.store_state();
    }

    if ((C_Flag = code_seen('C')) && code_has_value())
      Constant = code_value_float();

    if (code_seen('D')) {     // Disable the Unified Bed Leveling System
      blm.state.active = 0;
      SERIAL_PROTOCOLLNPGM("Unified Bed Leveling System de-activated.\n");
      blm.store_state();
    }

    if (code_seen('F')) {
      blm.state.G29_Correction_Fade_Height = 10.00;
      if (code_has_value()) {
        blm.state.G29_Correction_Fade_Height = code_value_float();
        blm.state.G29_Fade_Height_Multiplier = 1.0 / blm.state.G29_Correction_Fade_Height;
      }
      if (blm.state.G29_Correction_Fade_Height<0.0 || blm.state.G29_Correction_Fade_Height>100.0) {
        SERIAL_PROTOCOLLNPGM("?Bed Level Correction Fade Height Not Plausable.\n");
        blm.state.G29_Correction_Fade_Height = 10.00;
        blm.state.G29_Fade_Height_Multiplier = 1.0 / blm.state.G29_Correction_Fade_Height;
        return UBL_ERR;
      }
    }

    if ((Repeat_Flag = code_seen('R'))) {
      Repetition_Cnt = code_has_value() ? code_value_int() : 9999;
      if (Repetition_Cnt < 1) {
        SERIAL_PROTOCOLLNPGM("Invalid Repetition count.\n");
        return UBL_ERR;
      }
    }
    return UBL_OK;
  }

  /**
   * This function goes away after G29 debug is complete. But for right now, it is a handy
   * routine to dump binary data structures.
   */
  void dump(char *str, float f) {
    char *ptr;

    SERIAL_PROTOCOL(str);
    SERIAL_PROTOCOL_F(f, 8);
    SERIAL_PROTOCOL("  ");
    ptr = (char *)&f;
    for (uint8_t i = 0; i < 4; i++) {
      SERIAL_PROTOCOL("  ");
      prt_hex_byte(*ptr++);
    }
    SERIAL_PROTOCOL("  isnan()=");
    SERIAL_PROTOCOL(isnan(f));
    SERIAL_PROTOCOL("  isinf()=");
    SERIAL_PROTOCOL(isinf(f));

    constexpr float g = INFINITY;
    if (f == -g)
      SERIAL_PROTOCOL("  Minus Infinity detected.");

    SERIAL_EOL;
  }

  static int UBL_state_at_invokation = 0,
             UBL_state_recursion_chk = 0;

  void save_UBL_active_state_and_disable() {
    UBL_state_recursion_chk++;
    if (UBL_state_recursion_chk != 1) {
      SERIAL_ECHOLNPGM("save_UBL_active_state_and_disabled() called multiple times in a row.");
      lcd_setstatus("save_UBL_active() error", true);
      lcd_quick_feedback();
      return;
    }
    UBL_state_at_invokation = blm.state.active;
    blm.state.active = 0;
    return;
  }

  void restore_UBL_active_state_and_leave() {
    if (--UBL_state_recursion_chk) {
      SERIAL_ECHOLNPGM("restore_UBL_active_state_and_leave() called too many times.");
      lcd_setstatus("restore_UBL_active() error", true);
      lcd_quick_feedback();
      return;
    }
    blm.state.active = UBL_state_at_invokation;
  }

  /**
   * Much of the 'What?' command can be eliminated. But until we are fully debugged, it is
   * good to have the extra information. Soon... we prune this to just a few items
   */
  void G29_What_Command() {
    int k, i;
    k = E2END - Unified_Bed_Leveling_EEPROM_start;
    Statistics_Flag++;

    SERIAL_PROTOCOLPGM("Version #4: 10/30/2016 branch \n");
    SERIAL_PROTOCOLPGM("Unified Bed Leveling System ");
    if (blm.state.active)
      SERIAL_PROTOCOLPGM("Active.");
    else
      SERIAL_PROTOCOLPGM("Inactive.");
    SERIAL_PROTOCOLLNPGM("  -------------------------------------       <----<<<");  // These arrows are just to help me

    if (blm.state.EEPROM_storage_slot == 0xFFFF)  {
      SERIAL_PROTOCOLPGM("No Mesh Loaded.");
      SERIAL_PROTOCOLLNPGM("  -------------------------------------       <----<<<"); // These arrows are just to help me
      // find this info buried in the clutter
    }
    else {
      SERIAL_PROTOCOLPGM("Mesh: ");
      prt_hex_word(blm.state.EEPROM_storage_slot);
      SERIAL_PROTOCOLPGM(" Loaded. ");
      SERIAL_PROTOCOLLNPGM("  --------------------------------------------------------       <----<<<"); // These arrows are just to help me
      // find this info buried in the clutter
    }

    SERIAL_ECHOPAIR("\nG29_Correction_Fade_Height : ", blm.state.G29_Correction_Fade_Height );
    SERIAL_PROTOCOLPGM("  -------------------------------------       <----<<< \n");  // These arrows are just to help me
    // find this info buried in the clutter
    idle();

    SERIAL_ECHOPGM("z_offset: ");
    SERIAL_PROTOCOL_F(blm.state.z_offset, 6);
    SERIAL_PROTOCOLLNPGM("  ------------------------------------------------------------       <----<<<");

    SERIAL_PROTOCOLPGM("X-Axis Mesh Points at: ");
    for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++) {
      SERIAL_PROTOCOL_F( blm.map_x_index_to_bed_location(i), 1);
      SERIAL_PROTOCOLPGM("  ");
    }
    SERIAL_EOL;
    SERIAL_PROTOCOLPGM("Y-Axis Mesh Points at: ");
    for (i = 0; i < UBL_MESH_NUM_Y_POINTS; i++) {
      SERIAL_PROTOCOL_F( blm.map_y_index_to_bed_location(i), 1);
      SERIAL_PROTOCOLPGM("  ");
    }
    SERIAL_EOL;

    #if HAS_KILL
      SERIAL_ECHOPAIR("Kill pin on :", KILL_PIN);
      SERIAL_ECHOLNPAIR("  state:", READ(KILL_PIN));
    #endif

    SERIAL_ECHOLNPAIR("UBL_state_at_invokation :", UBL_state_at_invokation);
    SERIAL_ECHOLNPAIR("UBL_state_recursion_chk :", UBL_state_recursion_chk);

    SERIAL_EOL;
    SERIAL_PROTOCOLPGM("Free EEPROM space starts at: 0x");
    prt_hex_word(Unified_Bed_Leveling_EEPROM_start);
    SERIAL_EOL;
    idle();

    SERIAL_PROTOCOLPGM("end of EEPROM              : ");
    prt_hex_word(E2END);
    SERIAL_EOL;
    idle();

    SERIAL_PROTOCOLLNPAIR("sizeof(blm) :  ", (int)sizeof(blm));
    SERIAL_EOL;
    SERIAL_PROTOCOLLNPAIR("z_value[][] size: ", (int)sizeof(z_values));
    SERIAL_EOL;

    SERIAL_PROTOCOLPGM("EEPROM free for UBL: 0x");
    prt_hex_word(k);
    SERIAL_EOL;
    idle();

    SERIAL_PROTOCOLPGM("EEPROM can hold 0x");
    prt_hex_word(k / sizeof(z_values));
    SERIAL_PROTOCOLPGM(" meshes. \n");

    SERIAL_PROTOCOLPGM("sizeof(stat)     :");
    prt_hex_word(sizeof(blm.state));
    SERIAL_EOL;
    idle();

    SERIAL_ECHOPAIR("\nUBL_MESH_NUM_X_POINTS  ", UBL_MESH_NUM_X_POINTS);
    SERIAL_ECHOPAIR("\nUBL_MESH_NUM_Y_POINTS  ", UBL_MESH_NUM_Y_POINTS);
    SERIAL_ECHOPAIR("\nUBL_MESH_MIN_X         ", UBL_MESH_MIN_X);
    SERIAL_ECHOPAIR("\nUBL_MESH_MIN_Y         ", UBL_MESH_MIN_Y);
    SERIAL_ECHOPAIR("\nUBL_MESH_MAX_X         ", UBL_MESH_MAX_X);
    SERIAL_ECHOPAIR("\nUBL_MESH_MAX_Y         ", UBL_MESH_MAX_Y);
    SERIAL_ECHOPGM("\nMESH_X_DIST        ");
    SERIAL_PROTOCOL_F(MESH_X_DIST, 6);
    SERIAL_ECHOPGM("\nMESH_Y_DIST        ");
    SERIAL_PROTOCOL_F(MESH_Y_DIST, 6);
    SERIAL_EOL;
    idle();

    SERIAL_ECHOPAIR("\nsizeof(block_t): ", (int)sizeof(block_t));
    SERIAL_ECHOPAIR("\nsizeof(planner.block_buffer): ", (int)sizeof(planner.block_buffer));
    SERIAL_ECHOPAIR("\nsizeof(char): ", (int)sizeof(char));
    SERIAL_ECHOPAIR("   sizeof(unsigned char): ", (int)sizeof(unsigned char));
    SERIAL_ECHOPAIR("\nsizeof(int): ", (int)sizeof(int));
    SERIAL_ECHOPAIR("   sizeof(unsigned int): ", (int)sizeof(unsigned int));
    SERIAL_ECHOPAIR("\nsizeof(long): ", (int)sizeof(long));
    SERIAL_ECHOPAIR("   sizeof(unsigned long int): ", (int)sizeof(unsigned long int));
    SERIAL_ECHOPAIR("\nsizeof(float): ", (int)sizeof(float));
    SERIAL_ECHOPAIR("   sizeof(double): ", (int)sizeof(double));
    SERIAL_ECHOPAIR("\nsizeof(void *): ", (int)sizeof(void *));
    struct pf { void *p_f(); } ptr_func;
    SERIAL_ECHOPAIR("   sizeof(struct pf): ", (int)sizeof(pf));
    SERIAL_ECHOPAIR("   sizeof(void *()): ", (int)sizeof(ptr_func));
    SERIAL_EOL;

    idle();

    if (!blm.sanity_check())
      SERIAL_PROTOCOLLNPGM("Unified Bed Leveling sanity checks passed.");
  }

  /**
   * When we are fully debugged, the EEPROM dump command will get deleted also. But
   * right now, it is good to have the extra information. Soon... we prune this.
   */
  void G29_EEPROM_Dump() {
    unsigned char cccc;
    int i, j, kkkk;

    SERIAL_ECHO_START;
    SERIAL_ECHOPGM("EEPROM Dump:\n");
    for (i = 0; i < E2END + 1; i += 16) {
      if (i & 0x3 == 0) idle();
      prt_hex_word(i);
      SERIAL_ECHOPGM(": ");
      for (j = 0; j < 16; j++) {
        kkkk = i + j;
        eeprom_read_block(&cccc, (void *)kkkk, 1);
        prt_hex_byte(cccc);
        SERIAL_ECHO(' ');
      }
      SERIAL_EOL;
    }
    SERIAL_EOL;
    return;
  }

  /**
   * When we are fully debugged, this may go away. But there are some valid
   * use cases for the users. So we can wait and see what to do with it.
   */
  void G29_Kompare_Current_Mesh_to_Stored_Mesh()  {
    float tmp_z_values[UBL_MESH_NUM_X_POINTS][UBL_MESH_NUM_Y_POINTS];
    int i, j, k;

    if (!code_has_value()) {
      SERIAL_PROTOCOLLNPGM("?Mesh # required.\n");
      return;
    }
    Storage_Slot = code_value_int();

    k = E2END - sizeof(blm.state);
    j = (k - Unified_Bed_Leveling_EEPROM_start) / sizeof(tmp_z_values);

    if (Storage_Slot < 0 || Storage_Slot > j || Unified_Bed_Leveling_EEPROM_start <= 0) {
      SERIAL_PROTOCOLLNPGM("?EEPROM storage not available for use.\n");
      return;
    }

    j = k - (Storage_Slot + 1) * sizeof(tmp_z_values);
    eeprom_read_block((void *)&tmp_z_values, (void *)j, sizeof(tmp_z_values));

    SERIAL_ECHOPAIR("Subtracting Mesh ", Storage_Slot);
    SERIAL_PROTOCOLPGM(" loaded from EEPROM address ");   // Soon, we can remove the extra clutter of printing
    prt_hex_word(j);            // the address in the EEPROM where the Mesh is stored.
    SERIAL_EOL;

    for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++)
      for (j = 0; j < UBL_MESH_NUM_Y_POINTS; j++)
        z_values[i][j] = z_values[i][j] - tmp_z_values[i][j];
  }

  mesh_index_pair find_closest_mesh_point_of_type(Mesh_Point_Type type, float X, float Y, bool probe_as_reference, unsigned int bits[16]) {
    int i, j;
    float f, px, py, mx, my, dx, dy, closest = 99999.99;
    float current_x, current_y, distance;
    mesh_index_pair return_val;

    return_val.x_index = return_val.y_index = -1;

    current_x = current_position[X_AXIS];
    current_y = current_position[Y_AXIS];

    px = X;       // Get our reference position. Either the nozzle or
    py = Y;       // the probe location.
    if (probe_as_reference) {
      px -= X_PROBE_OFFSET_FROM_EXTRUDER;
      py -= Y_PROBE_OFFSET_FROM_EXTRUDER;
    }

    for (i = 0; i < UBL_MESH_NUM_X_POINTS; i++) {
      for (j = 0; j < UBL_MESH_NUM_Y_POINTS; j++) {

        if ( (type == INVALID && isnan(z_values[i][j]))  // Check to see if this location holds the right thing
          || (type == REAL && !isnan(z_values[i][j]))
          || (type == SET_IN_BITMAP && is_bit_set(bits, i, j))
        ) {

          // We only get here if we found a Mesh Point of the specified type

          mx = blm.map_x_index_to_bed_location(i); // Check if we can probe this mesh location
          my = blm.map_y_index_to_bed_location(j);

          // If we are using the probe as the reference
          // there are some locations we can't get to.
          // We prune these out of the list and ignore
          // them until the next Phase where we do the
          // manual nozzle probing.
          if (probe_as_reference
            && (mx < (MIN_PROBE_X) || mx > (MAX_PROBE_X))
            && (my < (MIN_PROBE_Y) || my > (MAX_PROBE_Y))
          ) continue;

          dx = px - mx;         // We can get to it. Let's see if it is the
          dy = py - my;         // closest location to the nozzle.
          distance = HYPOT(dx, dy);

          dx = current_x - mx;                    // We are going to add in a weighting factor that considers
          dy = current_y - my;                    // the current location of the nozzle. If two locations are equal
          distance += HYPOT(dx, dy) * 0.01;       // distance from the measurement location, we are going to give

          if (distance < closest) {
            closest = distance;       // We found a closer location with
            return_val.x_index = i;   // the specified type of mesh value.
            return_val.y_index = j;
            return_val.distance = closest;
          }
        }
      }
    }
    return return_val;
  }

  void fine_tune_mesh(float X_Pos, float Y_Pos, float Height_Value, bool do_UBL_MESH_Map) {
    mesh_index_pair location;
    float xProbe, yProbe, new_z;
    uint16_t i, not_done[16];
    long round_off;

    save_UBL_active_state_and_disable();
    memset(not_done, 0xFF, sizeof(not_done));

    #if ENABLED(ULTRA_LCD)
      lcd_setstatus("Fine Tuning Mesh.", true);
    #endif

    do_blocking_move_to_z(Z_CLEARANCE_DEPLOY_PROBE);
    do_blocking_move_to_xy(X_Pos, Y_Pos);
    do {
      if (do_UBL_MESH_Map) blm.display_map(1);

      location = find_closest_mesh_point_of_type( SET_IN_BITMAP, X_Pos,  Y_Pos, 0, not_done); // The '0' says we want to use the nozzle's position
                                                                                              // It doesn't matter if the probe can not reach this
                                                                                              // location. This is a manual edit of the Mesh Point.
      if (location.x_index < 0 && location.y_index < 0) continue; // abort if we can't find any more points.

      bit_clear(not_done, location.x_index, location.y_index);  // Mark this location as 'adjusted' so we will find a
                                                                // different location the next time through the loop

      xProbe = blm.map_x_index_to_bed_location(location.x_index);
      yProbe = blm.map_y_index_to_bed_location(location.y_index);
      if (xProbe < X_MIN_POS || xProbe > X_MAX_POS || yProbe < Y_MIN_POS || yProbe > Y_MAX_POS) { // In theory, we don't need this check.
        SERIAL_PROTOCOLLNPGM("?Error: Attempt to edit off the bed.");                             // This really can't happen, but for now,
        UBL_has_control_of_LCD_Panel = 0;                                                         // Let's do the check.
        goto FINE_TUNE_EXIT;
      }

      do_blocking_move_to_z(Z_CLEARANCE_DEPLOY_PROBE);    // Move the nozzle to where we are going to edit
      do_blocking_move_to_xy(xProbe, yProbe);
      new_z = z_values[location.x_index][location.y_index] + 0.001;

      round_off = (int32_t)(new_z * 1000.0 + 2.5); // we chop off the last digits just to be clean. We are rounding to the
      round_off -= (round_off % 5L); // closest 0 or 5 at the 3rd decimal place.
      new_z = ((float)(round_off)) / 1000.0;

      //SERIAL_ECHOPGM("Mesh Point Currently At:  ");
      //SERIAL_PROTOCOL_F(new_z, 6);
      //SERIAL_EOL;

      lcd_implementation_clear();
      lcd_mesh_edit_setup(new_z);
      UBL_has_control_of_LCD_Panel++;
      do {
        new_z = lcd_mesh_edit();
        idle();
      } while (!G29_lcd_clicked());

      UBL_has_control_of_LCD_Panel = 1; // There is a race condition for the Encoder Wheel getting clicked.
                                        // It could get detected in lcd_mesh_edit (actually _lcd_mesh_fine_tune( )
                                        // or here.
      millis_t nxt = millis() + 1500UL;
      lcd_return_to_status();
      while (G29_lcd_clicked()) { // debounce and watch for abort
        idle();
        if (ELAPSED(millis(), nxt)) {
          lcd_return_to_status();
          SERIAL_PROTOCOLLNPGM("\nFine Tuning of Mesh Stopped.");
          do_blocking_move_to_z(Z_CLEARANCE_DEPLOY_PROBE);
          lcd_setstatus("Mesh Editing Stopped", true);

          while (G29_lcd_clicked()) idle();

          UBL_has_control_of_LCD_Panel = 0;
          goto FINE_TUNE_EXIT;
        }
      }
      //UBL_has_control_of_LCD_Panel = 0;
      delay(20);                       // We don't want any switch noise.

      z_values[location.x_index][location.y_index] = new_z;

      lcd_implementation_clear();

    } while (location.x_index >= 0 && location.y_index >= 0 && --Repetition_Cnt);

    FINE_TUNE_EXIT:

    if (do_UBL_MESH_Map) blm.display_map(1);
    restore_UBL_active_state_and_leave();
    do_blocking_move_to_z(Z_CLEARANCE_DEPLOY_PROBE);

    do_blocking_move_to_xy(X_Pos, Y_Pos);

    UBL_has_control_of_LCD_Panel = 0;

    #if ENABLED(ULTRA_LCD)
      lcd_setstatus("Done Editing Mesh", true);
    #endif
    SERIAL_ECHOLNPGM("Done Editing Mesh.");
  }

#endif // AUTO_BED_LEVELING_UBL