Fixed "Change Filament E1/E2" to work during print (T1557)

- Found a better way to implement "Change Filament E1/E2" such that it
  will not crash Marlin when called in the middle of an ongoing print
  from either USB or SD card.
- Former "Change Filament E1/E2" implementation would only work before a
  print was begun.
- This fix applies to all dual toolheads.

Marlin/Conditionals_LulzBot.h

@@ -13,7 +13,7 @@
  * got disabled.
  */
 
-#define LULZBOT_FW_VERSION ".63" // Change this with each update
+#define LULZBOT_FW_VERSION ".64" // Change this with each update
 
 #if ( \
     !defined(LULZBOT_Gladiola_Mini) && \

Marlin/Marlin_main.cpp

@@ -6354,10 +6354,6 @@ inline void gcode_M17() {
     KEEPALIVE_STATE(IN_HANDLER);
   }
 
-  #if defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
-    void LULZBOT_RESTORE_ACTIVE_TOOLHEAD();
-  #endif
-
   static void resume_print(const float &load_length = 0, const float &initial_extrude_length = 0, const int8_t max_beep_count = 0) {
     bool nozzle_timed_out = false;
 
@@ -6458,10 +6454,6 @@ inline void gcode_M17() {
       lcd_advanced_pause_show_message(ADVANCED_PAUSE_MESSAGE_STATUS);
     #endif
 
-    #if defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
-    LULZBOT_RESTORE_ACTIVE_TOOLHEAD();
-    #endif
-
     #if ENABLED(SDSUPPORT)
       if (sd_print_paused) {
         card.startFileprint();
@@ -9725,6 +9717,7 @@ inline void gcode_M502() {
    *  U[distance] - Retract distance for removal (negative value) (manual reload)
    *  L[distance] - Extrude distance for insertion (positive value) (manual reload)
    *  B[count]    - Number of times to beep, -1 for indefinite (if equipped with a buzzer)
+   *  T[toolhead] - Select extruder for filament change
    *
    *  Default values are used for omitted arguments.
    *
@@ -9736,6 +9729,18 @@ inline void gcode_M502() {
       if (axis_unhomed_error()) home_all_axes();
     #endif
 
+    #if defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
+    // Change toolhead if specified
+    uint8_t active_extruder_before_filament_change = -1;
+    if(parser.seen('T')) {
+      const uint8_t extruder = parser.value_byte();
+      if(active_extruder != extruder) {
+        active_extruder_before_filament_change = active_extruder;
+        tool_change(extruder, 0, true);
+      }
+    }
+    #endif
+
     // Initial retract before move to filament change position
     const float retract = parser.seen('E') ? parser.value_axis_units(E_AXIS) : 0
       #ifdef PAUSE_PARK_RETRACT_LENGTH
@@ -9791,6 +9796,13 @@ inline void gcode_M502() {
       resume_print(load_length, ADVANCED_PAUSE_EXTRUDE_LENGTH, beep_count);
     }
 
+    #if defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
+    // Change toolhead if specified
+    if(active_extruder_before_filament_change != -1) {
+      tool_change(active_extruder_before_filament_change, 0, true);
+    }
+    #endif
+
     // Resume the print job timer if it was running
     if (job_running) print_job_timer.start();
   }

Marlin/ultralcd.cpp

@@ -894,37 +894,16 @@ void kill_screen(const char* lcd_msg) {
 #if defined(LULZBOT_REORDERED_MENUS) && defined(LULZBOT_USE_LCD_DISPLAY)
   void lcd_configuration_menu();
   void lcd_movement_menu();
-  void lcd_enqueue_filament_change();
   void lcd_show_custom_bootscreen();
   static void lcd_store_settings();
   static void lcd_load_settings();
 
   #if defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
-
-  void tool_change(const uint8_t tmp_extruder, const float fr_mm_s/*=0.0*/, bool no_move/*=false*/);
-
-  static uint8_t active_extruder_before_filament_change = -1;
-
-  void lcd_enqueue_filament_change_e0() {
-    if (axis_unhomed_error()) {lcd_return_to_status(); return;};
-    active_extruder_before_filament_change = active_extruder;
-    tool_change(0, 0, true);
-    lcd_enqueue_filament_change();
-  }
-
-  void lcd_enqueue_filament_change_e1() {
-    if (axis_unhomed_error()) {lcd_return_to_status(); return;};
-    active_extruder_before_filament_change = active_extruder;
-    tool_change(1, 0, true);
-    lcd_enqueue_filament_change();
-  }
-
-  void LULZBOT_RESTORE_ACTIVE_TOOLHEAD() {
-    if(active_extruder_before_filament_change > -1) {
-      tool_change(active_extruder_before_filament_change, 0, true);
-      active_extruder_before_filament_change = -1;
-    }
-  }
+  void lcd_enqueue_filament_change(uint8_t);
+  void lcd_enqueue_filament_change_e0() {lcd_enqueue_filament_change(0);}
+  void lcd_enqueue_filament_change_e1() {lcd_enqueue_filament_change(1);}
+  #else
+  void lcd_enqueue_filament_change();
   #endif
 
   void lcd_main_menu() {
@@ -1270,10 +1249,12 @@ void kill_screen(const char* lcd_msg) {
 
   #if ENABLED(ADVANCED_PAUSE_FEATURE)
 
-    void lcd_enqueue_filament_change() {
-      #if !defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
-        if (axis_unhomed_error()) {lcd_return_to_status(); return;}
+    void lcd_enqueue_filament_change(
+      #if defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
+        uint8_t extruder
       #endif
+    ) {
+
 
       #if ENABLED(PREVENT_COLD_EXTRUSION)
         if (!DEBUGGING(DRYRUN) && !thermalManager.allow_cold_extrude &&
@@ -1285,7 +1266,11 @@ void kill_screen(const char* lcd_msg) {
       #endif
 
       lcd_advanced_pause_show_message(ADVANCED_PAUSE_MESSAGE_INIT);
+      #if defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
+      enqueue_and_echo_commands_P(extruder == 0 ? PSTR("M600 B0 T0") : PSTR("M600 B0 T1"));
+      #else
       enqueue_and_echo_commands_P(PSTR("M600 B0"));
+      #endif
     }
 
   #endif // ADVANCED_PAUSE_FEATURE
@@ -2642,7 +2627,7 @@ void kill_screen(const char* lcd_msg) {
     //
     // Change filament
     //
-    #if ENABLED(ADVANCED_PAUSE_FEATURE)
+    #if ENABLED(ADVANCED_PAUSE_FEATURE) && !defined(LULZBOT_CHANGE_FILAMENT_DUAL_EXTRUDER_SUPPORT)
       if (!thermalManager.tooColdToExtrude(active_extruder) && !IS_SD_FILE_OPEN)
         MENU_ITEM(function, MSG_FILAMENTCHANGE, lcd_enqueue_filament_change);
     #endif