Experimental S-curve

(cherry picked from commit 5348de1)

# Conflicts:
#	Marlin/src/inc/SanityCheck.h
#	Marlin/src/module/stepper.cpp

Author: dbuezas

Marlin/src/inc/SanityCheck.h

@@ -866,8 +866,6 @@ static_assert(COUNT(arm) == LOGICAL_AXES, "AXIS_RELATIVE_MODES must contain " _L
   #if ENABLED(SMOOTH_LIN_ADVANCE)
     #ifndef CPU_32_BIT
       #error "SMOOTH_LIN_ADVANCE requires a 32-bit CPU."
-    #elif ENABLED(S_CURVE_ACCELERATION)
-      #error "SMOOTH_LIN_ADVANCE is not compatible with S_CURVE_ACCELERATION."
     #elif ENABLED(NONLINEAR_EXTRUSION)
       #error "SMOOTH_LIN_ADVANCE doesn't currently support NONLINEAR_EXTRUSION."
     #elif ENABLED(INPUT_SHAPING_E_SYNC) && NONE(INPUT_SHAPING_X, INPUT_SHAPING_Y)

Marlin/src/module/stepper.cpp

@@ -2929,14 +2929,42 @@ hal_timer_t Stepper::block_phase_isr() {
       }
 
     #endif // INPUT_SHAPING_E_SYNC
+    #if ENABLED(S_CURVE_ACCELERATION)
+      static int32_t bezier_A_backup; 
+      static int32_t bezier_B_backup; 
+      static int32_t bezier_C_backup; 
+      static uint32_t bezier_F_backup; 
+      static uint32_t bezier_AV_backup; 
+      void Stepper::backup_bezier(){
+        bezier_A_backup = bezier_A;
+        bezier_B_backup = bezier_B;
+        bezier_C_backup = bezier_C;
+        bezier_F_backup = bezier_F;
+        bezier_AV_backup = bezier_AV;
+      }
+      void Stepper::recover_bezier(){
+        bezier_A = bezier_A_backup;
+        bezier_B = bezier_B_backup;
+        bezier_C = bezier_C_backup;
+        bezier_F = bezier_F_backup;
+        bezier_AV = bezier_AV_backup;
+      }
+    #endif
 
     int32_t smooth_lin_adv_lookahead(uint32_t stepper_ticks) {
       for (uint8_t i = 0; block_t *block = planner.get_future_block(i); i++) {
         if (block->is_sync()) continue;
         if (stepper_ticks <= block->acceleration_time) {
           if (!block->use_advance_lead) return 0;
-          uint32_t rate = STEP_MULTIPLY(stepper_ticks, block->acceleration_rate) + block->initial_rate;
-          NOMORE(rate, block->nominal_rate);
+          #if ENABLED(S_CURVE_ACCELERATION)
+            Stepper::backup_bezier();
+            Stepper::_calc_bezier_curve_coeffs(block->initial_rate, block->cruise_rate, block->acceleration_time_inverse);
+            uint32_t rate = Stepper::_eval_bezier_curve(stepper_ticks);
+            Stepper::recover_bezier();
+          #else
+            uint32_t rate = STEP_MULTIPLY(stepper_ticks, block->acceleration_rate) + block->initial_rate;
+            NOMORE(rate, block->nominal_rate);
+          #endif
           return MULT_Q(30, rate, block->e_step_ratio_q30);
         }
         stepper_ticks -= block->acceleration_time;
@@ -2949,13 +2977,20 @@ hal_timer_t Stepper::block_phase_isr() {
 
         if (stepper_ticks <= block->deceleration_time) {
           if (!block->use_advance_lead) return 0;
-          uint32_t rate = STEP_MULTIPLY(stepper_ticks, block->acceleration_rate);
-          if (rate < block->cruise_rate) {
-            rate = block->cruise_rate - rate;
-            NOLESS(rate, block->final_rate);
-          }
-          else
-            rate = block->final_rate;
+          #if ENABLED(S_CURVE_ACCELERATION)
+            Stepper::backup_bezier();
+            Stepper::_calc_bezier_curve_coeffs(block->cruise_rate, block->final_rate, block->deceleration_time_inverse);
+            uint32_t rate = Stepper::_eval_bezier_curve(stepper_ticks);
+            Stepper::recover_bezier();
+          #else
+            uint32_t rate = STEP_MULTIPLY(stepper_ticks, block->acceleration_rate);
+            if (rate < block->cruise_rate) {
+              rate = block->cruise_rate - rate;
+              NOLESS(rate, block->final_rate);
+            }
+            else
+              rate = block->final_rate;
+          #endif
           return MULT_Q(30, rate, block->e_step_ratio_q30);
         }
         stepper_ticks -= block->deceleration_time;

Marlin/src/module/stepper.h

@@ -533,6 +533,10 @@ class Stepper {
       #if ENABLED(SMOOTH_LIN_ADVANCE)
         static void set_la_interval(const int32_t rate);
         static hal_timer_t smooth_lin_adv_isr();
+        #if ENABLED(S_CURVE_ACCELERATION)
+          static void backup_bezier();
+          static void recover_bezier();
+        #endif
       #endif
     #endif
 
@@ -743,8 +747,10 @@ class Stepper {
     #endif
 
     #if ENABLED(S_CURVE_ACCELERATION)
+      public:
       static void _calc_bezier_curve_coeffs(const int32_t v0, const int32_t v1, const uint32_t av);
       static int32_t _eval_bezier_curve(const uint32_t curr_step);
+      private:
     #endif
 
     #if HAS_MOTOR_CURRENT_SPI || HAS_MOTOR_CURRENT_PWM