Save 7714 bytes of program memory when doing AUTO_BED_LEVELING_LINEAR (MarlinFirmware#7276)

We can save more and a pile of RAM by eleminating the eqnBVector and
EqnAMatrix arrays next.

Author: Roxy-3D

Marlin/Marlin_main.cpp

@@ -261,7 +261,7 @@
 #if HAS_ABL
   #include "vector_3.h"
   #if ENABLED(AUTO_BED_LEVELING_LINEAR)
-    #include "qr_solve.h"
+    #include "least_squares_fit.h"
   #endif
 #elif ENABLED(MESH_BED_LEVELING)
   #include "mesh_bed_leveling.h"
@@ -4336,8 +4336,8 @@ void home_all_axes() { gcode_G28(true); }
         ABL_VAR int indexIntoAB[GRID_MAX_POINTS_X][GRID_MAX_POINTS_Y];
 
         ABL_VAR float eqnAMatrix[GRID_MAX_POINTS * 3], // "A" matrix of the linear system of equations
-                     eqnBVector[GRID_MAX_POINTS],     // "B" vector of Z points
-                     mean;
+                      eqnBVector[GRID_MAX_POINTS],     // "B" vector of Z points
+                      mean;
       #endif
 
     #elif ENABLED(AUTO_BED_LEVELING_3POINT)
@@ -4353,6 +4353,11 @@ void home_all_axes() { gcode_G28(true); }
 
     #endif // AUTO_BED_LEVELING_3POINT
 
+    #if ENABLED(AUTO_BED_LEVELING_LINEAR)
+      struct linear_fit_data lsf_results;
+      incremental_LSF_reset(&lsf_results);
+    #endif
+
     /**
      * On the initial G29 fetch command parameters.
      */
@@ -4549,11 +4554,7 @@ void home_all_axes() { gcode_G28(true); }
           abl_should_enable = false;
         }
 
-      #elif ENABLED(AUTO_BED_LEVELING_LINEAR)
-
-        mean = 0.0;
-
-      #endif // AUTO_BED_LEVELING_LINEAR
+      #endif // AUTO_BED_LEVELING_BILINEAR
 
       #if ENABLED(AUTO_BED_LEVELING_3POINT)
 
@@ -4616,11 +4617,11 @@ void home_all_axes() { gcode_G28(true); }
 
         #if ENABLED(AUTO_BED_LEVELING_LINEAR)
 
-          mean += measured_z;
-          eqnBVector[abl_probe_index] = measured_z;
-          eqnAMatrix[abl_probe_index + 0 * abl2] = xProbe;
-          eqnAMatrix[abl_probe_index + 1 * abl2] = yProbe;
-          eqnAMatrix[abl_probe_index + 2 * abl2] = 1;
+//        mean += measured_z;                                  // I believe this is unused code?
+//        eqnBVector[abl_probe_index] = measured_z;            // I believe this is unused code?
+//        eqnAMatrix[abl_probe_index + 0 * abl2] = xProbe;     // I believe this is unused code?
+//        eqnAMatrix[abl_probe_index + 1 * abl2] = yProbe;     // I believe this is unused code?
+//        eqnAMatrix[abl_probe_index + 2 * abl2] = 1;          // I believe this is unused code?
 
         #elif ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
@@ -4794,6 +4795,11 @@ void home_all_axes() { gcode_G28(true); }
               eqnAMatrix[abl_probe_index + 1 * abl2] = yProbe;
               eqnAMatrix[abl_probe_index + 2 * abl2] = 1;
 
+              incremental_LSF(&lsf_results, xProbe, yProbe, measured_z);
+
+          #if ENABLED(AUTO_BED_LEVELING_LINEAR)
+            indexIntoAB[xCount][yCount] = abl_probe_index;
+          #endif
             #elif ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
               z_values[xCount][yCount] = measured_z + zoffset;
@@ -4894,7 +4900,11 @@ void home_all_axes() { gcode_G28(true); }
        * so Vx = -a Vy = -b Vz = 1 (we want the vector facing towards positive Z
        */
       float plane_equation_coefficients[3];
-      qr_solve(plane_equation_coefficients, abl2, 3, eqnAMatrix, eqnBVector);
+
+      finish_incremental_LSF(&lsf_results);
+      plane_equation_coefficients[0] = -lsf_results.A;  // We should be able to eliminate the '-' on these three lines and down below
+      plane_equation_coefficients[1] = -lsf_results.B;  // but that is not yet tested.
+      plane_equation_coefficients[2] = -lsf_results.D;
 
       mean /= abl2;
 
@@ -4916,7 +4926,7 @@ void home_all_axes() { gcode_G28(true); }
       // Create the matrix but don't correct the position yet
       if (!dryrun) {
         planner.bed_level_matrix = matrix_3x3::create_look_at(
-          vector_3(-plane_equation_coefficients[0], -plane_equation_coefficients[1], 1)
+          vector_3(-plane_equation_coefficients[0], -plane_equation_coefficients[1], 1)    // We can eleminate the '-' here and up above
         );
       }
 

Marlin/least_squares_fit.cpp

@@ -34,7 +34,7 @@
 
 #include "MarlinConfig.h"
 
-#if ENABLED(AUTO_BED_LEVELING_UBL)  // Currently only used by UBL, but is applicable to Grid Based (Linear) Bed Leveling
+#if ENABLED(AUTO_BED_LEVELING_UBL) || ENABLED(AUTO_BED_LEVELING_LINEAR)
 
 #include "macros.h"
 #include <math.h>
@@ -68,4 +68,4 @@ int finish_incremental_LSF(struct linear_fit_data *lsf) {
   return 0;
 }
 
-#endif // AUTO_BED_LEVELING_UBL
+#endif // AUTO_BED_LEVELING_UBL || ENABLED(AUTO_BED_LEVELING_LINEAR)  

Marlin/least_squares_fit.h

@@ -34,7 +34,7 @@
 
 #include "MarlinConfig.h"
 
-#if ENABLED(AUTO_BED_LEVELING_UBL)  // Currently only used by UBL, but is applicable to Grid Based (Linear) Bed Leveling
+#if ENABLED(AUTO_BED_LEVELING_UBL) || ENABLED(AUTO_BED_LEVELING_LINEAR)    
 
 #include "Marlin.h"
 #include "macros.h"