Support for multiple filament runout sensors

Marlin/Configuration.h

 #endif
 
 /**
- * Filament Runout Sensor
- * A mechanical or opto endstop is used to check for the presence of filament.
+ * Filament Runout Sensors
+ * Mechanical or opto endstops are used to check for the presence of filament.
  *
- * RAMPS-based boards use SERVO3_PIN.
- * For other boards you may need to define FIL_RUNOUT_PIN.
- * By default the firmware assumes HIGH = has filament, LOW = ran out
+ * RAMPS-based boards use SERVO3_PIN for the first runout sensor.
+ * For other boards you may need to define FIL_RUNOUT_PIN, FIL_RUNOUT2_PIN, etc.
+ * By default the firmware assumes HIGH=FILAMENT PRESENT.
  */
 //#define FILAMENT_RUNOUT_SENSOR
 #if ENABLED(FILAMENT_RUNOUT_SENSOR)
+  #define NUM_RUNOUT_SENSORS   1     // Number of sensors, up to one per extruder. Define a FIL_RUNOUT#_PIN for each.
   #define FIL_RUNOUT_INVERTING false // set to true to invert the logic of the sensor.
   #define FIL_RUNOUT_PULLUP          // Use internal pullup for filament runout pins.
   //#define FIL_RUNOUT_PULLDOWN      // Use internal pulldown for filament runout pins.

Marlin/src/Marlin.cpp

   #endif
 }
 
-#if ENABLED(FILAMENT_RUNOUT_SENSOR)
-
-  void setup_filrunoutpin() {
-    #if ENABLED(FIL_RUNOUT_PULLUP)
-      SET_INPUT_PULLUP(FIL_RUNOUT_PIN);
-    #elif ENABLED(FIL_RUNOUT_PULLDOWN)
-      SET_INPUT_PULLDOWN(FIL_RUNOUT_PIN);
-    #else
-      SET_INPUT(FIL_RUNOUT_PIN);
-    #endif
-  }
-
-#endif
-
 void setup_powerhold() {
   #if HAS_SUICIDE
     OUT_WRITE(SUICIDE_PIN, HIGH);
 void manage_inactivity(bool ignore_stepper_queue/*=false*/) {
 
   #if ENABLED(FILAMENT_RUNOUT_SENSOR)
-    if ((IS_SD_PRINTING || print_job_timer.isRunning())
-      && READ(FIL_RUNOUT_PIN) == FIL_RUNOUT_INVERTING
-      && thermalManager.targetHotEnoughToExtrude(active_extruder)
-    )
-      handle_filament_runout();
+    runout.run();
   #endif
 
   if (commands_in_queue < BUFSIZE) get_available_commands();
   #endif
 
   #if ENABLED(FILAMENT_RUNOUT_SENSOR)
-    setup_filrunoutpin();
+    runout.setup();
   #endif
 
   setup_killpin();

Marlin/src/feature/pause.cpp

   planner.set_e_position_mm(destination[E_AXIS] = current_position[E_AXIS] = resume_position[E_AXIS]);
 
   #if ENABLED(FILAMENT_RUNOUT_SENSOR)
-    filament_ran_out = false;
+    runout.reset();
   #endif
 
   #if ENABLED(ULTIPANEL)

Marlin/src/feature/runout.cpp

  * feature/runout.cpp - Runout sensor support
  */
 
-#include "../inc/MarlinConfig.h"
+#include "../inc/MarlinConfigPre.h"
 
 #if ENABLED(FILAMENT_RUNOUT_SENSOR)
 
-#include "../module/stepper.h"
-#include "../gcode/queue.h"
+#include "runout.h"
 
-bool filament_ran_out = false;
+FilamentRunoutSensor runout;
 
-void handle_filament_runout() {
-  if (!filament_ran_out) {
-    filament_ran_out = true;
-    enqueue_and_echo_commands_P(PSTR(FILAMENT_RUNOUT_SCRIPT));
-    stepper.synchronize();
-  }
+bool FilamentRunoutSensor::filament_ran_out; // = false;
+
+void FilamentRunoutSensor::setup() {
+
+  #if ENABLED(FIL_RUNOUT_PULLUP)
+    #define INIT_RUNOUT_PIN(P) SET_INPUT_PULLUP(P)
+  #elif ENABLED(FIL_RUNOUT_PULLDOWN)
+    #define INIT_RUNOUT_PIN(P) SET_INPUT_PULLDOWN(P)
+  #else
+    #define INIT_RUNOUT_PIN(P) SET_INPUT(P)
+  #endif
+
+  INIT_RUNOUT_PIN(FIL_RUNOUT_PIN);
+  #if NUM_RUNOUT_SENSORS > 1
+    INIT_RUNOUT_PIN(FIL_RUNOUT2_PIN);
+    #if NUM_RUNOUT_SENSORS > 2
+      INIT_RUNOUT_PIN(FIL_RUNOUT3_PIN);
+      #if NUM_RUNOUT_SENSORS > 3
+        INIT_RUNOUT_PIN(FIL_RUNOUT4_PIN);
+        #if NUM_RUNOUT_SENSORS > 4
+          INIT_RUNOUT_PIN(FIL_RUNOUT5_PIN);
+        #endif
+      #endif
+    #endif
+  #endif
 }
 
 #endif // FILAMENT_RUNOUT_SENSOR

Marlin/src/feature/runout.h

 #ifndef _RUNOUT_H_
 #define _RUNOUT_H_
 
-extern bool filament_ran_out;
+#include "../sd/cardreader.h"
+#include "../module/printcounter.h"
+#include "../module/stepper.h"
+#include "../gcode/queue.h"
 
-void handle_filament_runout();
+#include "../inc/MarlinConfig.h"
+
+class FilamentRunoutSensor {
+
+  FilamentRunoutSensor() {}
+
+  static bool filament_ran_out;
+  static void setup();
+
+  FORCE_INLINE static reset() { filament_ran_out = false; }
+
+  FORCE_INLINE static bool check() {
+    #if NUM_RUNOUT_SENSORS < 2
+      // A single sensor applying to all extruders
+      return READ(FIL_RUNOUT_PIN) == FIL_RUNOUT_INVERTING;
+    #else
+      // Read the sensor for the active extruder
+      switch (active_extruder) {
+        case 0: return READ(FIL_RUNOUT_PIN) == FIL_RUNOUT_INVERTING;
+        case 1: return READ(FIL_RUNOUT2_PIN) == FIL_RUNOUT_INVERTING;
+        #if NUM_RUNOUT_SENSORS > 2
+          case 2: return READ(FIL_RUNOUT3_PIN) == FIL_RUNOUT_INVERTING;
+          #if NUM_RUNOUT_SENSORS > 3
+            case 3: return READ(FIL_RUNOUT4_PIN) == FIL_RUNOUT_INVERTING;
+            #if NUM_RUNOUT_SENSORS > 4
+              case 4: return READ(FIL_RUNOUT5_PIN) == FIL_RUNOUT_INVERTING;
+            #endif
+          #endif
+        #endif
+      }
+    #endif
+    return false;
+  }
+
+  FORCE_INLINE static void run() {
+    if ((IS_SD_PRINTING || print_job_timer.isRunning()) && check() && !filament_ran_out) {
+      filament_ran_out = true;
+      enqueue_and_echo_commands_P(PSTR(FILAMENT_RUNOUT_SCRIPT));
+      stepper.synchronize();
+    }
+  }
+
+};
+
+extern FilamentRunoutSensor runout;
 
 #endif // _RUNOUT_H_

Marlin/src/inc/Conditionals_post.h

 
 // Sensors
 #define HAS_FILAMENT_WIDTH_SENSOR (PIN_EXISTS(FILWIDTH))
-#define HAS_FIL_RUNOUT (PIN_EXISTS(FIL_RUNOUT))
 
 // User Interface
 #define HAS_HOME (PIN_EXISTS(HOME))

Marlin/src/inc/SanityCheck.h

 #endif
 
 /**
- * Filament Runout needs a pin and either SD Support or Auto print start detection
+ * Filament Runout needs one or more pins and either SD Support or Auto print start detection
  */
 #if ENABLED(FILAMENT_RUNOUT_SENSOR)
-  #if !HAS_FIL_RUNOUT
+  #if !PIN_EXISTS(FIL_RUNOUT)
     #error "FILAMENT_RUNOUT_SENSOR requires FIL_RUNOUT_PIN."
+  #elif NUM_RUNOUT_SENSORS > E_STEPPERS
+    #error "NUM_RUNOUT_SENSORS cannot exceed the number of E steppers."
+  #elif NUM_RUNOUT_SENSORS > 1 && !PIN_EXISTS(FIL_RUNOUT2)
+    #error "FILAMENT_RUNOUT_SENSOR with NUM_RUNOUT_SENSORS > 1 requires FIL_RUNOUT2_PIN."
+  #elif NUM_RUNOUT_SENSORS > 2 && !PIN_EXISTS(FIL_RUNOUT3)
+    #error "FILAMENT_RUNOUT_SENSOR with NUM_RUNOUT_SENSORS > 2 requires FIL_RUNOUT3_PIN."
+  #elif NUM_RUNOUT_SENSORS > 3 && !PIN_EXISTS(FIL_RUNOUT4)
+    #error "FILAMENT_RUNOUT_SENSOR with NUM_RUNOUT_SENSORS > 3 requires FIL_RUNOUT4_PIN."
+  #elif NUM_RUNOUT_SENSORS > 4 && !PIN_EXISTS(FIL_RUNOUT5)
+    #error "FILAMENT_RUNOUT_SENSOR with NUM_RUNOUT_SENSORS > 4 requires FIL_RUNOUT5_PIN."
   #elif DISABLED(SDSUPPORT) && DISABLED(PRINTJOB_TIMER_AUTOSTART)
     #error "FILAMENT_RUNOUT_SENSOR requires SDSUPPORT or PRINTJOB_TIMER_AUTOSTART."
   #elif DISABLED(ADVANCED_PAUSE_FEATURE)