Introduce temp watch protection for the bed

When setting the bed temp via M140/M190 if the thermistor does not read an increase of WATCH_BED_TEMP_INCREASE degrees by WATCH_BED_TEMP_PERIOD seconds then it will throw "Error:Heating failed, system stopped! Heater_ID: bed" and call the kill() function.

Conflicts:
	Marlin/Configuration_adv.h

Marlin/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/Felix/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/Hephestos/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/Hephestos_2/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/K8200/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/RigidBot/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/SCARA/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/TAZ4/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/WITBOX/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/delta/biv2.5/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 120   // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 4 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/delta/generic/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/delta/kossel_mini/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/delta/kossel_pro/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/delta/kossel_xl/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/makibox/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/example_configurations/tvrrug/Round2/Configuration_adv.h

 #if ENABLED(THERMAL_PROTECTION_BED)
   #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
   #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
+
+  /**
+   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
+   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
+   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
+   * but only if the current temperature is far enough below the target for a reliable test.
+   *
+   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
+   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
+   */
+  #define WATCH_BED_TEMP_PERIOD 60                // Seconds
+  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
 #endif
 
 #if ENABLED(PIDTEMP)

Marlin/temperature.cpp

 static float analog2tempBed(int raw);
 static void updateTemperaturesFromRawValues();
 
-#if ENABLED(THERMAL_PROTECTION_HOTENDS)
+#if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
   int watch_target_temp[EXTRUDERS] = { 0 };
   millis_t watch_heater_next_ms[EXTRUDERS] = { 0 };
 #endif
 
+#if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+  int watch_target_bed_temp = 0;
+  millis_t watch_bed_next_ms = 0;
+#endif
+
 #ifndef SOFT_PWM_SCALE
   #define SOFT_PWM_SCALE 0
 #endif
     if (ct < max(HEATER_0_MINTEMP, 0.01)) min_temp_error(0);
   #endif
 
-  #if ENABLED(THERMAL_PROTECTION_HOTENDS) || DISABLED(PIDTEMPBED) || HAS_AUTO_FAN
+  #if (ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0) || (ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0) || DISABLED(PIDTEMPBED) || HAS_AUTO_FAN
     millis_t ms = millis();
   #endif
 
     soft_pwm[e] = current_temperature[e] > minttemp[e] && current_temperature[e] < maxttemp[e] ? (int)pid_output >> 1 : 0;
 
     // Check if the temperature is failing to increase
-    #if ENABLED(THERMAL_PROTECTION_HOTENDS)
+    #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
 
       // Is it time to check this extruder's heater?
       if (watch_heater_next_ms[e] && ELAPSED(ms, watch_heater_next_ms[e])) {
 
     #endif // THERMAL_PROTECTION_HOTENDS
 
+    // Check if the temperature is failing to increase
+    #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+
+      // Is it time to check the bed?
+      if (watch_bed_next_ms && ELAPSED(ms, watch_bed_next_ms)) {
+        // Has it failed to increase enough?
+        if (degBed() < watch_target_bed_temp) {
+          // Stop!
+          _temp_error(-1, PSTR(MSG_T_HEATING_FAILED), PSTR(MSG_HEATING_FAILED_LCD));
+        }
+        else {
+          // Start again if the target is still far off
+          start_watching_bed();
+        }
+      }
+
+    #endif // THERMAL_PROTECTION_HOTENDS
+
     #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
       if (fabs(current_temperature[0] - redundant_temperature) > MAX_REDUNDANT_TEMP_SENSOR_DIFF) {
         _temp_error(0, PSTR(MSG_REDUNDANCY), PSTR(MSG_ERR_REDUNDANT_TEMP));
   #endif //BED_MAXTEMP
 }
 
-#if ENABLED(THERMAL_PROTECTION_HOTENDS)
+#if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
   /**
    * Start Heating Sanity Check for hotends that are below
    * their target temperature by a configurable margin.
   }
 #endif
 
+#if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+  /**
+   * Start Heating Sanity Check for hotends that are below
+   * their target temperature by a configurable margin.
+   * This is called when the temperature is set. (M140, M190)
+   */
+  void start_watching_bed() {
+    if (degBed() < degTargetBed() - (WATCH_BED_TEMP_INCREASE + TEMP_BED_HYSTERESIS + 1)) {
+      watch_target_bed_temp = degBed() + WATCH_BED_TEMP_INCREASE;
+      watch_bed_next_ms = millis() + (WATCH_BED_TEMP_PERIOD) * 1000UL;
+    }
+    else
+      watch_bed_next_ms = 0;
+  }
+#endif
+
 #if ENABLED(THERMAL_PROTECTION_HOTENDS) || ENABLED(THERMAL_PROTECTION_BED)
 
   void thermal_runaway_protection(TRState* state, millis_t* timer, float temperature, float target_temperature, int heater_id, int period_seconds, int hysteresis_degc) {

Marlin/temperature.h

 FORCE_INLINE float degTargetHotend(uint8_t extruder) { return target_temperature[extruder]; }
 FORCE_INLINE float degTargetBed() { return target_temperature_bed; }
 
-#if ENABLED(THERMAL_PROTECTION_HOTENDS)
+#if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
   void start_watching_heater(int e = 0);
 #endif
 
+#if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+  void start_watching_bed();
+#endif
+
 FORCE_INLINE void setTargetHotend(const float& celsius, uint8_t extruder) {
   target_temperature[extruder] = celsius;
-  #if ENABLED(THERMAL_PROTECTION_HOTENDS)
+  #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
     start_watching_heater(extruder);
   #endif
 }
-FORCE_INLINE void setTargetBed(const float& celsius) { target_temperature_bed = celsius; }
+FORCE_INLINE void setTargetBed(const float& celsius) {
+  target_temperature_bed = celsius;
+  #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+    start_watching_bed();
+  #endif
+}
 
 FORCE_INLINE bool isHeatingHotend(uint8_t extruder) { return target_temperature[extruder] > current_temperature[extruder]; }
 FORCE_INLINE bool isHeatingBed() { return target_temperature_bed > current_temperature_bed; }

Marlin/ultralcd.cpp

 /**
  * Watch temperature callbacks
  */
-#if ENABLED(THERMAL_PROTECTION_HOTENDS)
+#if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
   #if TEMP_SENSOR_0 != 0
     void watch_temp_callback_E0() { start_watching_heater(0); }
   #endif
   #endif // EXTRUDERS > 3
 #endif
 
+#if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
+  #if TEMP_SENSOR_BED != 0
+    void watch_temp_callback_bed() { start_watching_bed(); }
+  #endif
+#else
+  #if TEMP_SENSOR_BED != 0
+    void watch_temp_callback_bed() {}
+  #endif
+#endif
+
 /**
  *
  * "Tune" submenu
   // Bed:
   //
   #if TEMP_SENSOR_BED != 0
-    MENU_MULTIPLIER_ITEM_EDIT(int3, MSG_BED, &target_temperature_bed, 0, BED_MAXTEMP - 15);
+    MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(int3, MSG_BED, &target_temperature_bed, 0, BED_MAXTEMP - 15, watch_temp_callback_bed);
   #endif
 
   //