Replace division in planner with multiplication

Marlin/Marlin_main.cpp

   // Send "ok" after commands by default
   for (int8_t i = 0; i < BUFSIZE; i++) send_ok[i] = true;
 
-  // loads data from EEPROM if available else uses defaults (and resets step acceleration rate)
+  // Load data from EEPROM if available (or use defaults)
+  // This also updates variables in the planner, elsewhere
   Config_RetrieveSettings();
 
   // Initialize current position based on home_offset
   memcpy(current_position, home_offset, sizeof(home_offset));
 
-  #if ENABLED(DELTA) || ENABLED(SCARA)
-    // Vital to init kinematic equivalent for X0 Y0 Z0
-    SYNC_PLAN_POSITION_KINEMATIC();
-  #endif
+  // Vital to init stepper/planner equivalent for current_position
+  SYNC_PLAN_POSITION_KINEMATIC();
 
   thermalManager.init();    // Initialize temperature loop
 
       }
     }
   }
+  planner.refresh_positioning();
 }
 
 /**

Marlin/configuration_store.cpp

   // steps per s2 needs to be updated to agree with units per s2
   planner.reset_acceleration_rates();
 
+  // Make sure delta kinematics are updated before refreshing the
+  // planner position so the stepper counts will be set correctly.
   #if ENABLED(DELTA)
     recalc_delta_settings(delta_radius, delta_diagonal_rod);
   #endif
 
+  // Refresh steps_to_mm with the reciprocal of axis_steps_per_mm
+  // and init stepper.count[], planner.position[] with current_position
+  planner.refresh_positioning();
+
   #if ENABLED(PIDTEMP)
     thermalManager.updatePID();
   #endif

Marlin/planner.cpp

 
 float Planner::max_feedrate_mm_s[NUM_AXIS]; // Max speeds in mm per second
 float Planner::axis_steps_per_mm[NUM_AXIS];
+float Planner::steps_to_mm[NUM_AXIS];
 unsigned long Planner::max_acceleration_steps_per_s2[NUM_AXIS];
 unsigned long Planner::max_acceleration_mm_per_s2[NUM_AXIS]; // Use M201 to override by software
 
   #if ENABLED(COREXY) || ENABLED(COREXZ) || ENABLED(COREYZ)
     float delta_mm[6];
     #if ENABLED(COREXY)
-      delta_mm[X_HEAD] = dx / axis_steps_per_mm[A_AXIS];
-      delta_mm[Y_HEAD] = dy / axis_steps_per_mm[B_AXIS];
-      delta_mm[Z_AXIS] = dz / axis_steps_per_mm[Z_AXIS];
-      delta_mm[A_AXIS] = (dx + dy) / axis_steps_per_mm[A_AXIS];
-      delta_mm[B_AXIS] = (dx - dy) / axis_steps_per_mm[B_AXIS];
+      delta_mm[X_HEAD] = dx * steps_to_mm[A_AXIS];
+      delta_mm[Y_HEAD] = dy * steps_to_mm[B_AXIS];
+      delta_mm[Z_AXIS] = dz * steps_to_mm[Z_AXIS];
+      delta_mm[A_AXIS] = (dx + dy) * steps_to_mm[A_AXIS];
+      delta_mm[B_AXIS] = (dx - dy) * steps_to_mm[B_AXIS];
     #elif ENABLED(COREXZ)
-      delta_mm[X_HEAD] = dx / axis_steps_per_mm[A_AXIS];
-      delta_mm[Y_AXIS] = dy / axis_steps_per_mm[Y_AXIS];
-      delta_mm[Z_HEAD] = dz / axis_steps_per_mm[C_AXIS];
-      delta_mm[A_AXIS] = (dx + dz) / axis_steps_per_mm[A_AXIS];
-      delta_mm[C_AXIS] = (dx - dz) / axis_steps_per_mm[C_AXIS];
+      delta_mm[X_HEAD] = dx * steps_to_mm[A_AXIS];
+      delta_mm[Y_AXIS] = dy * steps_to_mm[Y_AXIS];
+      delta_mm[Z_HEAD] = dz * steps_to_mm[C_AXIS];
+      delta_mm[A_AXIS] = (dx + dz) * steps_to_mm[A_AXIS];
+      delta_mm[C_AXIS] = (dx - dz) * steps_to_mm[C_AXIS];
     #elif ENABLED(COREYZ)
-      delta_mm[X_AXIS] = dx / axis_steps_per_mm[X_AXIS];
-      delta_mm[Y_HEAD] = dy / axis_steps_per_mm[B_AXIS];
-      delta_mm[Z_HEAD] = dz / axis_steps_per_mm[C_AXIS];
-      delta_mm[B_AXIS] = (dy + dz) / axis_steps_per_mm[B_AXIS];
-      delta_mm[C_AXIS] = (dy - dz) / axis_steps_per_mm[C_AXIS];
+      delta_mm[X_AXIS] = dx * steps_to_mm[X_AXIS];
+      delta_mm[Y_HEAD] = dy * steps_to_mm[B_AXIS];
+      delta_mm[Z_HEAD] = dz * steps_to_mm[C_AXIS];
+      delta_mm[B_AXIS] = (dy + dz) * steps_to_mm[B_AXIS];
+      delta_mm[C_AXIS] = (dy - dz) * steps_to_mm[C_AXIS];
     #endif
   #else
     float delta_mm[4];
       // so calculate distance in steps first, then do one division
       // at the end to get millimeters
     #else
-      delta_mm[X_AXIS] = dx / axis_steps_per_mm[X_AXIS];
-      delta_mm[Y_AXIS] = dy / axis_steps_per_mm[Y_AXIS];
-      delta_mm[Z_AXIS] = dz / axis_steps_per_mm[Z_AXIS];
+      delta_mm[X_AXIS] = dx * steps_to_mm[X_AXIS];
+      delta_mm[Y_AXIS] = dy * steps_to_mm[Y_AXIS];
+      delta_mm[Z_AXIS] = dz * steps_to_mm[Z_AXIS];
     #endif
   #endif
-  delta_mm[E_AXIS] = (de / axis_steps_per_mm[E_AXIS]) * volumetric_multiplier[extruder] * extruder_multiplier[extruder] / 100.0;
+  delta_mm[E_AXIS] = (de * steps_to_mm[E_AXIS]) * volumetric_multiplier[extruder] * extruder_multiplier[extruder] / 100.0;
 
   if (block->steps[X_AXIS] <= dropsegments && block->steps[Y_AXIS] <= dropsegments && block->steps[Z_AXIS] <= dropsegments) {
     block->millimeters = fabs(delta_mm[E_AXIS]);
       #endif
     )
       #if ENABLED(DELTA)
-        / axis_steps_per_mm[X_AXIS]
+        * steps_to_mm[X_AXIS]
       #endif
     ;
   }
 void Planner::set_e_position_mm(const float& e) {
   position[E_AXIS] = lround(e * axis_steps_per_mm[E_AXIS]);
   stepper.set_e_position(position[E_AXIS]);
+  previous_speed[E_AXIS] = 0.0;
 }
 
 // Recalculate the steps/s^2 acceleration rates, based on the mm/s^2
     max_acceleration_steps_per_s2[i] = max_acceleration_mm_per_s2[i] * axis_steps_per_mm[i];
 }
 
+// Recalculate position, steps_to_mm if axis_steps_per_mm changes!
+void Planner::refresh_positioning() {
+  LOOP_XYZE(i) planner.steps_to_mm[i] = 1.0 / planner.axis_steps_per_mm[i];
+  set_position_mm(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
+  reset_acceleration_rates();
+}
+
 #if ENABLED(AUTOTEMP)
 
   void Planner::autotemp_M109() {

Marlin/planner.h

 
     static float max_feedrate_mm_s[NUM_AXIS]; // Max speeds in mm per second
     static float axis_steps_per_mm[NUM_AXIS];
+    static float steps_to_mm[NUM_AXIS];
     static unsigned long max_acceleration_steps_per_s2[NUM_AXIS];
     static unsigned long max_acceleration_mm_per_s2[NUM_AXIS]; // Use M201 to override by software
 
 
     /**
      * The current position of the tool in absolute steps
-     * Reclculated if any axis_steps_per_mm are changed by gcode
+     * Recalculated if any axis_steps_per_mm are changed by gcode
      */
     static long position[NUM_AXIS];
 
      */
 
     static void reset_acceleration_rates();
+    static void refresh_positioning();
 
     // Manage fans, paste pressure, etc.
     static void check_axes_activity();

Marlin/stepper.cpp

   #else
     axis_steps = position(axis);
   #endif
-  return axis_steps / planner.axis_steps_per_mm[axis];
+  return axis_steps * planner.steps_to_mm[axis];
 }
 
 void Stepper::finish_and_disable() {

Marlin/stepper.h

     // Triggered position of an axis in mm (not core-savvy)
     //
     static FORCE_INLINE float triggered_position_mm(AxisEnum axis) {
-      return endstops_trigsteps[axis] / planner.axis_steps_per_mm[axis];
+      return endstops_trigsteps[axis] * planner.steps_to_mm[axis];
     }
 
     #if ENABLED(LIN_ADVANCE)

Marlin/temperature.cpp

               lpq[lpq_ptr] = 0;
             }
             if (++lpq_ptr >= lpq_len) lpq_ptr = 0;
-            cTerm[HOTEND_INDEX] = (lpq[lpq_ptr] / planner.axis_steps_per_mm[E_AXIS]) * PID_PARAM(Kc, HOTEND_INDEX);
+            cTerm[HOTEND_INDEX] = (lpq[lpq_ptr] * planner.steps_to_mm[E_AXIS]) * PID_PARAM(Kc, HOTEND_INDEX);
             pid_output += cTerm[HOTEND_INDEX];
           }
         #endif //PID_ADD_EXTRUSION_RATE

Marlin/ultralcd.cpp

       }
       if (lcdDrawUpdate)
         lcd_implementation_drawedit(msg, ftostr43sign(
-          ((1000 * babysteps_done) / planner.axis_steps_per_mm[axis]) * 0.001f
+          ((1000 * babysteps_done) * planner.steps_to_mm[axis]) * 0.001f
         ));
     }
 
   }
 
   static void _reset_acceleration_rates() { planner.reset_acceleration_rates(); }
+  static void _planner_refresh_positioning() { planner.refresh_positioning(); }
 
   /**
    *
     MENU_ITEM_EDIT_CALLBACK(long5, MSG_AMAX MSG_E, &planner.max_acceleration_mm_per_s2[E_AXIS], 100, 99000, _reset_acceleration_rates);
     MENU_ITEM_EDIT(float5, MSG_A_RETRACT, &planner.retract_acceleration, 100, 99000);
     MENU_ITEM_EDIT(float5, MSG_A_TRAVEL, &planner.travel_acceleration, 100, 99000);
-    MENU_ITEM_EDIT(float52, MSG_XSTEPS, &planner.axis_steps_per_mm[X_AXIS], 5, 9999);
-    MENU_ITEM_EDIT(float52, MSG_YSTEPS, &planner.axis_steps_per_mm[Y_AXIS], 5, 9999);
+    MENU_ITEM_EDIT_CALLBACK(float52, MSG_XSTEPS, &planner.axis_steps_per_mm[X_AXIS], 5, 9999, _planner_refresh_positioning);
+    MENU_ITEM_EDIT_CALLBACK(float52, MSG_YSTEPS, &planner.axis_steps_per_mm[Y_AXIS], 5, 9999, _planner_refresh_positioning);
     #if ENABLED(DELTA)
-      MENU_ITEM_EDIT(float52, MSG_ZSTEPS, &planner.axis_steps_per_mm[Z_AXIS], 5, 9999);
+      MENU_ITEM_EDIT_CALLBACK(float52, MSG_ZSTEPS, &planner.axis_steps_per_mm[Z_AXIS], 5, 9999, _planner_refresh_positioning);
     #else
-      MENU_ITEM_EDIT(float51, MSG_ZSTEPS, &planner.axis_steps_per_mm[Z_AXIS], 5, 9999);
+      MENU_ITEM_EDIT_CALLBACK(float51, MSG_ZSTEPS, &planner.axis_steps_per_mm[Z_AXIS], 5, 9999, _planner_refresh_positioning);
     #endif
-    MENU_ITEM_EDIT(float51, MSG_ESTEPS, &planner.axis_steps_per_mm[E_AXIS], 5, 9999);
+    MENU_ITEM_EDIT_CALLBACK(float51, MSG_ESTEPS, &planner.axis_steps_per_mm[E_AXIS], 5, 9999, _planner_refresh_positioning);
     #if ENABLED(ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
       MENU_ITEM_EDIT(bool, MSG_ENDSTOP_ABORT, &stepper.abort_on_endstop_hit);
     #endif