✨ Redundant Part Cooling Fan (#21888)

Co-authored-by: Scott Lahteine <github@thinkyhead.com>

Marlin/Configuration_adv.h

   //#define USE_OCR2A_AS_TOP
 #endif
 
+/**
+ * Use one of the PWM fans as a redundant part-cooling fan
+ */
+//#define REDUNDANT_PART_COOLING_FAN 2  // Index of the fan to sync with FAN 0.
+
 // @section extruder
 
 /**

Marlin/src/gcode/temp/M106_M107.cpp

  */
 void GcodeSuite::M106() {
   const uint8_t pfan = parser.byteval('P', _ALT_P);
+  if (pfan >= _CNT_P) return;
+  #if REDUNDANT_PART_COOLING_FAN
+    if (pfan == REDUNDANT_PART_COOLING_FAN) return;
+  #endif
 
-  if (pfan < _CNT_P) {
-
-    #if ENABLED(EXTRA_FAN_SPEED)
-      const uint16_t t = parser.intval('T');
-      if (t > 0) return thermalManager.set_temp_fan_speed(pfan, t);
-    #endif
+  #if ENABLED(EXTRA_FAN_SPEED)
+    const uint16_t t = parser.intval('T');
+    if (t > 0) return thermalManager.set_temp_fan_speed(pfan, t);
+  #endif
 
-    const uint16_t dspeed = parser.seen_test('A') ? thermalManager.fan_speed[active_extruder] : 255;
+  const uint16_t dspeed = parser.seen_test('A') ? thermalManager.fan_speed[active_extruder] : 255;
 
-    uint16_t speed = dspeed;
+  uint16_t speed = dspeed;
 
-    // Accept 'I' if temperature presets are defined
-    #if PREHEAT_COUNT
-      const bool got_preset = parser.seenval('I');
-      if (got_preset) speed = ui.material_preset[_MIN(parser.value_byte(), PREHEAT_COUNT - 1)].fan_speed;
-    #else
-      constexpr bool got_preset = false;
-    #endif
+  // Accept 'I' if temperature presets are defined
+  #if PREHEAT_COUNT
+    const bool got_preset = parser.seenval('I');
+    if (got_preset) speed = ui.material_preset[_MIN(parser.value_byte(), PREHEAT_COUNT - 1)].fan_speed;
+  #else
+    constexpr bool got_preset = false;
+  #endif
 
-    if (!got_preset && parser.seenval('S'))
-      speed = parser.value_ushort();
+  if (!got_preset && parser.seenval('S'))
+    speed = parser.value_ushort();
 
-    TERN_(FOAMCUTTER_XYUV, speed *= 2.55); // Get command in % of max heat
+  TERN_(FOAMCUTTER_XYUV, speed *= 2.55); // Get command in % of max heat
 
-    // Set speed, with constraint
-    thermalManager.set_fan_speed(pfan, speed);
+  // Set speed, with constraint
+  thermalManager.set_fan_speed(pfan, speed);
 
-    TERN_(LASER_SYNCHRONOUS_M106_M107, planner.buffer_sync_block(BLOCK_FLAG_SYNC_FANS));
+  TERN_(LASER_SYNCHRONOUS_M106_M107, planner.buffer_sync_block(BLOCK_FLAG_SYNC_FANS));
 
-    if (TERN0(DUAL_X_CARRIAGE, idex_is_duplicating()))  // pfan == 0 when duplicating
-      thermalManager.set_fan_speed(1 - pfan, speed);
-  }
+  if (TERN0(DUAL_X_CARRIAGE, idex_is_duplicating()))  // pfan == 0 when duplicating
+    thermalManager.set_fan_speed(1 - pfan, speed);
 }
 
 /**
 void GcodeSuite::M107() {
   const uint8_t pfan = parser.byteval('P', _ALT_P);
   if (pfan >= _CNT_P) return;
+  #if REDUNDANT_PART_COOLING_FAN
+    if (pfan == REDUNDANT_PART_COOLING_FAN) return;
+  #endif
 
   thermalManager.set_fan_speed(pfan, 0);
 

Marlin/src/inc/SanityCheck.h

   #endif
 #endif
 
+#ifdef REDUNDANT_PART_COOLING_FAN
+  #if FAN_COUNT < 2
+    #error "REDUNDANT_PART_COOLING_FAN requires a board with at least two PWM fans."
+  #else
+    static_assert(WITHIN(REDUNDANT_PART_COOLING_FAN, 1, FAN_COUNT - 1), "REDUNDANT_PART_COOLING_FAN must be between 1 and " STRINGIFY(DECREMENT(FAN_COUNT)) ".");
+  #endif
+#endif
+
 /**
  * Case Light requirements
  */

Marlin/src/lcd/menu/menu_temperature.cpp

     if (indb >= 0 && ui.material_preset[indb].bed_temp > 0) setTargetBed(ui.material_preset[indb].bed_temp);
   #endif
   #if HAS_FAN
-    if (indh >= 0)
-      set_fan_speed(active_extruder < (FAN_COUNT) ? active_extruder : 0, ui.material_preset[indh].fan_speed);
+    if (indh >= 0) {
+      const uint8_t fan_index = active_extruder < (FAN_COUNT) ? active_extruder : 0;
+      if (true
+        #if REDUNDANT_PART_COOLING_FAN
+          && fan_index != REDUNDANT_PART_COOLING_FAN
+        #endif
+      ) set_fan_speed(fan_index, ui.material_preset[indh].fan_speed);
+    }
   #endif
   ui.return_to_status();
 }
     #if HAS_FAN0
       _FAN_EDIT_ITEMS(0,FIRST_FAN_SPEED);
     #endif
-    #if HAS_FAN1
+    #if HAS_FAN1 && REDUNDANT_PART_COOLING_FAN != 1
       FAN_EDIT_ITEMS(1);
     #elif SNFAN(1)
       singlenozzle_item(1);
     #endif
-    #if HAS_FAN2
+    #if HAS_FAN2 && REDUNDANT_PART_COOLING_FAN != 2
       FAN_EDIT_ITEMS(2);
     #elif SNFAN(2)
       singlenozzle_item(2);
     #endif
-    #if HAS_FAN3
+    #if HAS_FAN3 && REDUNDANT_PART_COOLING_FAN != 3
       FAN_EDIT_ITEMS(3);
     #elif SNFAN(3)
       singlenozzle_item(3);
     #endif
-    #if HAS_FAN4
+    #if HAS_FAN4 && REDUNDANT_PART_COOLING_FAN != 4
       FAN_EDIT_ITEMS(4);
     #elif SNFAN(4)
       singlenozzle_item(4);
     #endif
-    #if HAS_FAN5
+    #if HAS_FAN5 && REDUNDANT_PART_COOLING_FAN != 5
       FAN_EDIT_ITEMS(5);
     #elif SNFAN(5)
       singlenozzle_item(5);
     #endif
-    #if HAS_FAN6
+    #if HAS_FAN6 && REDUNDANT_PART_COOLING_FAN != 6
       FAN_EDIT_ITEMS(6);
     #elif SNFAN(6)
       singlenozzle_item(6);
     #endif
-    #if HAS_FAN7
+    #if HAS_FAN7 && REDUNDANT_PART_COOLING_FAN != 7
       FAN_EDIT_ITEMS(7);
     #elif SNFAN(7)
       singlenozzle_item(7);

Marlin/src/module/temperature.cpp

     if (fan >= FAN_COUNT) return;
 
     fan_speed[fan] = speed;
+    #if REDUNDANT_PART_COOLING_FAN
+      if (fan == 0) fan_speed[REDUNDANT_PART_COOLING_FAN] = speed;
+    #endif
 
     TERN_(REPORT_FAN_CHANGE, report_fan_speed(fan));
   }

buildroot/tests/mega2560

 #
 restore_configs
 opt_set MOTHERBOARD BOARD_AZTEEG_X3_PRO MIXING_STEPPERS 5 LCD_LANGUAGE ru \
-        NUM_RUNOUT_SENSORS E_STEPPERS FIL_RUNOUT2_PIN 16 FIL_RUNOUT3_PIN 17 FIL_RUNOUT4_PIN 4 FIL_RUNOUT5_PIN 5
+        NUM_RUNOUT_SENSORS E_STEPPERS REDUNDANT_PART_COOLING_FAN 1 \
+        FIL_RUNOUT2_PIN 16 FIL_RUNOUT3_PIN 17 FIL_RUNOUT4_PIN 4 FIL_RUNOUT5_PIN 5
 opt_enable MIXING_EXTRUDER GRADIENT_MIX GRADIENT_VTOOL CR10_STOCKDISPLAY \
            USE_CONTROLLER_FAN CONTROLLER_FAN_EDITABLE CONTROLLER_FAN_IGNORE_Z \
            FILAMENT_RUNOUT_SENSOR ADVANCED_PAUSE_FEATURE NOZZLE_PARK_FEATURE