[pull] bugfix-2.1.x from MarlinFirmware:bugfix-2.1.x

Marlin/Configuration_adv.h

@@ -1237,16 +1237,29 @@
 
   #define FTM_POLYS                             // Disable POLY5/6 to save ~3k of Flash. Preserves TRAPEZOIDAL.
   #if ENABLED(FTM_POLYS)
-    #define FTM_TRAJECTORY_TYPE TRAPEZOIDAL     // Block acceleration profile (TRAPEZOIDAL, POLY5, POLY6)
-                                                // TRAPEZOIDAL: Continuous Velocity. Max acceleration is respected.
-                                                // POLY5:       Like POLY6 with 1.5x but uses less CPU.
-                                                // POLY6:       Continuous Acceleration (aka S_CURVE).
-                                                // POLY trajectories not only reduce resonances without rounding corners, but also
-                                                // reduce extruder strain due to linear advance.
-
     #define FTM_POLY6_ACCELERATION_OVERSHOOT 1.875f // Max acceleration overshoot factor for POLY6 (1.25 to 1.875)
   #endif
 
+  /**
+   * FTM Constant-Jolt Trajectory (7-phase S-curve).
+   * Jolt is the rate of change of acceleration, not related to Marlin's "classic jerk."
+   * Ramps acceleration gradually so max acceleration is limited by max speed and distance traveled.
+   */
+  //#define FTM_CONSTANT_JOLT
+  #if ENABLED(FTM_CONSTANT_JOLT)
+    #define FTM_DEFAULT_JOLT 250.0f         // (m/s³) Default jolt for constant-jolt trajectory.
+                                            // Higher values print faster at the cost of increased resonance and extruder stress
+  #endif
+
+  // Block acceleration profile
+  // :[ 'TRAPEZOIDAL', 'POLY5', 'POLY6', 'CONSTANT_JOLT' ]
+  #define FTM_TRAJECTORY_TYPE TRAPEZOIDAL   //   TRAPEZOIDAL: Continuous Velocity. Max acceleration is respected.
+                                            //         POLY5: Like POLY6 with 1.5x but uses less CPU. Requires FTM_POLYS.
+                                            //         POLY6: Continuous Acceleration (aka S_CURVE). Requires FTM_POLYS.
+                                            // CONSTANT_JOLT: 7-phase S-curve. Requires FTM_CONSTANT_JOLT.
+                                            // POLY trajectories not only reduce resonances without rounding corners, but
+                                            // also reduce extruder strain due to linear advance.
+
   /**
    * Advanced configuration
    */

Marlin/Version.h

@@ -41,7 +41,7 @@
  * here we define this default string as the date where the latest release
  * version was tagged.
  */
-//#define STRING_DISTRIBUTION_DATE "2026-06-28"
+//#define STRING_DISTRIBUTION_DATE "2026-06-29"
 
 /**
  * The protocol for communication to the host. Protocol indicates communication

Marlin/src/gcode/feature/ft_motion/M494.cpp

@@ -30,14 +30,20 @@
 #include "../../../lcd/marlinui.h"
 
 void say_ftm_settings() {
-  #if ANY(FTM_POLYS, FTM_SMOOTHING)
+  #if ANY(FTM_POLYS, FTM_SMOOTHING, FTM_CONSTANT_JOLT)
     const ft_config_t &c = ftMotion.cfg;
   #endif
 
-  #if ENABLED(FTM_POLYS)
+  #if HAS_FTM_TRAJECTORY_SELECTION
     SERIAL_ECHOLN(F("  Trajectory: "), ftMotion.getTrajectoryName(), C('('), (uint8_t)ftMotion.getTrajectoryType(), C(')'));
-    if (ftMotion.getTrajectoryType() == TrajectoryType::POLY6)
-      SERIAL_ECHOLNPGM("  Poly6 Overshoot: ", p_float_t(c.poly6_acceleration_overshoot, 3));
+    #if ENABLED(FTM_POLYS)
+      if (ftMotion.getTrajectoryType() == TrajectoryType::POLY6)
+        SERIAL_ECHOLNPGM("  Poly6 Overshoot: ", p_float_t(c.poly6_acceleration_overshoot, 3));
+    #endif
+    #if ENABLED(FTM_CONSTANT_JOLT)
+      if (ftMotion.getTrajectoryType() == TrajectoryType::CONSTANT_JOLT)
+        SERIAL_ECHOLNPGM("  Jolt: ", p_float_t(c.jolt / 1000.0f, 1), " m/s^3");
+    #endif
   #endif
 
   #if ENABLED(FTM_SMOOTHING)
@@ -52,7 +58,7 @@ void GcodeSuite::M494_report(const bool forReplay/*=true*/) {
   report_heading_etc(forReplay, F("FT Motion"));
   SERIAL_ECHOPGM("  M494 T", (uint8_t)ftMotion.getTrajectoryType());
 
-  #if ANY(FTM_POLYS, FTM_SMOOTHING)
+  #if ANY(FTM_POLYS, FTM_SMOOTHING, FTM_CONSTANT_JOLT)
     const ft_config_t &c = ftMotion.cfg;
   #endif
 
@@ -70,15 +76,21 @@ void GcodeSuite::M494_report(const bool forReplay/*=true*/) {
       SERIAL_ECHOPGM(" O", c.poly6_acceleration_overshoot);
   #endif
 
+  #if ENABLED(FTM_CONSTANT_JOLT)
+    if (ftMotion.getTrajectoryType() == TrajectoryType::CONSTANT_JOLT)
+      SERIAL_ECHOPGM(" J", c.jolt / 1000.0f);
+  #endif
+
   SERIAL_EOL();
 }
 
 /**
  * M494: Set Fixed-time Motion Control parameters
  *
  * Parameters:
- *    T<type> Set trajectory generator type (0=TRAPEZOIDAL, 1=POLY5, 2=POLY6)
+ *    T<type> Set trajectory generator type (0=TRAPEZOIDAL, 1=POLY5, 2=POLY6, 3=CONSTANT_JOLT)
  *    O<overshoot> Set acceleration overshoot for POLY6 (1.25-1.875)
+ *    J<jolt> Set maximum jolt for CONSTANT_JOLT (m/s³, positive)
  *    X<time> Set smoothing time for the X axis
  *    Y<time> Set smoothing time for the Y axis
  *    Z<time> Set smoothing time for the Z axis
@@ -87,16 +99,23 @@ void GcodeSuite::M494_report(const bool forReplay/*=true*/) {
 void GcodeSuite::M494() {
   bool report = !parser.seen_any();
 
-  #if ENABLED(FTM_POLYS)
+  #if HAS_FTM_TRAJECTORY_SELECTION
 
     // Parse trajectory type parameter.
     if (parser.seenval('T')) {
       if (ftMotion.updateTrajectoryType(TrajectoryType(parser.value_int())))
         report = true;
       else
-        SERIAL_ECHOLN(F("?Invalid "), F("(T)rajectory type value. Use 0=TRAPEZOIDAL, 1=POLY5, 2=POLY6"));
+        SERIAL_ECHOLN(F("?Invalid (T)rajectory type value. (0=TRAPEZOIDAL"
+          TERN_(FTM_POLYS, ", 1=POLY5, 2=POLY6")
+          TERN_(FTM_CONSTANT_JOLT, ", 3=CONSTANT_JOLT")
+          ")"));
     }
 
+  #endif // HAS_FTM_TRAJECTORY_SELECTION
+
+  #if ENABLED(FTM_POLYS)
+
     // Parse overshoot parameter.
     if (parser.seenval('O')) {
       const float val = parser.value_float();
@@ -110,6 +129,16 @@ void GcodeSuite::M494() {
 
   #endif // FTM_POLYS
 
+  #if ENABLED(FTM_CONSTANT_JOLT)
+
+    // Parse jolt parameter (user provides m/s³, stored internally as mm/s³).
+    if (parser.seenval('J')) {
+      ftMotion.cfg.set_jolt(parser.value_float() * 1000.0f);
+      report = true;
+    }
+
+  #endif // FTM_CONSTANT_JOLT
+
   #if ENABLED(FTM_SMOOTHING)
 
     auto smooth_set = [](AxisEnum axis, char axis_name) {

Marlin/src/inc/Conditionals-4-adv.h

@@ -370,6 +370,13 @@
   #if ANY(FTM_DIR_CHANGE_HOLD_X, FTM_DIR_CHANGE_HOLD_Y, FTM_DIR_CHANGE_HOLD_Z, FTM_DIR_CHANGE_HOLD_E)
     #define HAS_FTM_DIR_CHANGE_HOLD 1
   #endif
+  #if ANY(FTM_POLYS, FTM_CONSTANT_JOLT)
+    #define HAS_FTM_TRAJECTORY_SELECTION 1
+  #endif
+  // Default trajectory type when not explicitly set
+  #ifndef FTM_TRAJECTORY_TYPE
+    #define FTM_TRAJECTORY_TYPE TRAPEZOIDAL
+  #endif
 #endif
 
 // Standard Motion

Marlin/src/inc/Version.h

@@ -42,7 +42,7 @@
  * version was tagged.
  */
 #ifndef STRING_DISTRIBUTION_DATE
-  #define STRING_DISTRIBUTION_DATE "2026-06-28"
+  #define STRING_DISTRIBUTION_DATE "2026-06-29"
 #endif
 
 /**

Marlin/src/lcd/language/language_en.h

@@ -838,6 +838,8 @@ namespace LanguageNarrow_en {
   LSTR MSG_FTM_TRAPEZOIDAL                = _UxGT("Trapezoidal");
   LSTR MSG_FTM_POLY5                      = _UxGT("5th Order");
   LSTR MSG_FTM_POLY6                      = _UxGT("6th Order");
+  LSTR MSG_FTM_CONSTANT_JOLT              = _UxGT("Constant Jolt");
+  LSTR MSG_FTM_JOLT                       = _UxGT("Jolt (m/s3)");
   LSTR MSG_FTM_TRAJECTORY                 = _UxGT("Trajectory: $");
   LSTR MSG_FILAMENT_EN                    = _UxGT("Filament *");
   LSTR MSG_SEGMENTS_PER_SECOND            = _UxGT("Segments/Sec");

Marlin/src/lcd/menu/menu_motion.cpp

@@ -428,7 +428,7 @@ void menu_move() {
     END_MENU();
   }
 
-  #if ENABLED(FTM_POLYS)
+  #if HAS_FTM_TRAJECTORY_SELECTION
 
     void menu_ftm_trajectory_generator() {
       const TrajectoryType traj_type = ftMotion.getTrajectoryType();
@@ -438,17 +438,24 @@ void menu_move() {
       if (traj_type != TrajectoryType::TRAPEZOIDAL) ACTION_ITEM(MSG_FTM_TRAPEZOIDAL, []{
         queue.inject(TS(F("M494"), 'T', int(TrajectoryType::TRAPEZOIDAL))); ui.go_back();
       });
-      if (traj_type != TrajectoryType::POLY5) ACTION_ITEM(MSG_FTM_POLY5, []{
-        queue.inject(TS(F("M494"), 'T', int(TrajectoryType::POLY5))); ui.go_back();
-      });
-      if (traj_type != TrajectoryType::POLY6) ACTION_ITEM(MSG_FTM_POLY6, []{
-        queue.inject(TS(F("M494"), 'T', int(TrajectoryType::POLY6))); ui.go_back();
-      });
+      #if ENABLED(FTM_POLYS)
+        if (traj_type != TrajectoryType::POLY5) ACTION_ITEM(MSG_FTM_POLY5, []{
+          queue.inject(TS(F("M494"), 'T', int(TrajectoryType::POLY5))); ui.go_back();
+        });
+        if (traj_type != TrajectoryType::POLY6) ACTION_ITEM(MSG_FTM_POLY6, []{
+          queue.inject(TS(F("M494"), 'T', int(TrajectoryType::POLY6))); ui.go_back();
+        });
+      #endif
+      #if ENABLED(FTM_CONSTANT_JOLT)
+        if (traj_type != TrajectoryType::CONSTANT_JOLT) ACTION_ITEM(MSG_FTM_CONSTANT_JOLT, []{
+          queue.inject(TS(F("M494"), 'T', int(TrajectoryType::CONSTANT_JOLT))); ui.go_back();
+        });
+      #endif
 
       END_MENU();
     }
 
-  #endif // FTM_POLYS
+  #endif // HAS_FTM_TRAJECTORY_SELECTION
 
   #if HAS_DYNAMIC_FREQ
 
@@ -548,14 +555,24 @@ void menu_move() {
     // Show only when FT Motion is active (or optionally always show)
     if (TERN(FT_MOTION_NO_MENU_TOGGLE, true, c.active)) {
 
-      #if ENABLED(FTM_POLYS)
+      #if HAS_FTM_TRAJECTORY_SELECTION
         SUBMENU_S(ftMotion.getTrajectoryName(), MSG_FTM_TRAJECTORY, menu_ftm_trajectory_generator);
-        if (ftMotion.getTrajectoryType() == TrajectoryType::POLY6) {
-          editable.decimal = c.poly6_acceleration_overshoot;
-          EDIT_ITEM(float42_52, MSG_FTM_POLY6_OVERSHOOT, &editable.decimal, 1.25f, 1.875f, []{
-            queue.inject(TS(F("M494"), 'O', editable.decimal));
-          });
-        }
+        #if ENABLED(FTM_POLYS)
+          if (ftMotion.getTrajectoryType() == TrajectoryType::POLY6) {
+            editable.decimal = c.poly6_acceleration_overshoot;
+            EDIT_ITEM(float42_52, MSG_FTM_POLY6_OVERSHOOT, &editable.decimal, 1.25f, 1.875f, []{
+              queue.inject(TS(F("M494"), 'O', editable.decimal));
+            });
+          }
+        #endif
+        #if ENABLED(FTM_CONSTANT_JOLT)
+          if (ftMotion.getTrajectoryType() == TrajectoryType::CONSTANT_JOLT) {
+            editable.decimal = c.jolt / 1000.0f;
+            EDIT_ITEM(float4, MSG_FTM_JOLT, &editable.decimal, 1.0f, 10000.0f, []{
+              queue.inject(TS(F("M494"), 'J', editable.decimal));
+            });
+          }
+        #endif
       #endif
 
       CARTES_MAP(_FTM_AXIS_SUBMENU);
@@ -576,7 +593,7 @@ void menu_move() {
       // Copy Flash strings to RAM for C-string substitution
       // For U8G paged rendering check and skip extra string copy
 
-      #if ENABLED(FTM_POLYS)
+      #if HAS_FTM_TRAJECTORY_SELECTION
         #if CACHE_FOR_SPEED
           bool got_t = false;
         #endif
@@ -592,7 +609,7 @@ void menu_move() {
 
     #else // !__AVR__
 
-      #if ENABLED(FTM_POLYS)
+      #if HAS_FTM_TRAJECTORY_SELECTION
         auto _traj_name = []{ return ftMotion.getTrajectoryName(); };
       #endif
 
@@ -601,14 +618,24 @@ void menu_move() {
     START_MENU();
     BACK_ITEM(MSG_TUNE);
 
-    #if ENABLED(FTM_POLYS)
+    #if HAS_FTM_TRAJECTORY_SELECTION
       SUBMENU_S(_traj_name(), MSG_FTM_TRAJECTORY, menu_ftm_trajectory_generator);
-      if (ftMotion.getTrajectoryType() == TrajectoryType::POLY6) {
-        editable.decimal = ftMotion.cfg.poly6_acceleration_overshoot;
-        EDIT_ITEM(float42_52, MSG_FTM_POLY6_OVERSHOOT, &editable.decimal, 1.25f, 1.875f, []{
-          queue.inject(TS(F("M494"), 'O', editable.decimal));
-        });
-      }
+      #if ENABLED(FTM_POLYS)
+        if (ftMotion.getTrajectoryType() == TrajectoryType::POLY6) {
+          editable.decimal = ftMotion.cfg.poly6_acceleration_overshoot;
+          EDIT_ITEM(float42_52, MSG_FTM_POLY6_OVERSHOOT, &editable.decimal, 1.25f, 1.875f, []{
+            queue.inject(TS(F("M494"), 'O', editable.decimal));
+          });
+        }
+      #endif
+      #if ENABLED(FTM_CONSTANT_JOLT)
+        if (ftMotion.getTrajectoryType() == TrajectoryType::CONSTANT_JOLT) {
+          editable.decimal = ftMotion.cfg.jolt / 1000.0f;
+          EDIT_ITEM(float4, MSG_FTM_JOLT, &editable.decimal, 1.0f, 10000.0f, []{
+            queue.inject(TS(F("M494"), 'J', editable.decimal));
+          });
+        }
+      #endif
     #endif
 
     SHAPED_MAP(_FTM_AXIS_SUBMENU);