Followup to new endstop interrupts feature

- Fix typos, verbiage
- Fix naming of `setup_endstop_interrupts`
- Some formatting, indentation, spacing

Marlin/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/Marlin_main.cpp

 #if ENABLED(ENDSTOP_INTERRUPTS_FEATURE)
   #include "endstop_interrupts.h"
 #endif
+
 /**
  * Look here for descriptions of G-codes:
  *  - http://linuxcnc.org/handbook/gcode/g-code.html
   #endif
 
   #if ENABLED(ENDSTOP_INTERRUPTS_FEATURE)
-    setup_enstop_interrupts();
+    setup_endstop_interrupts();
   #endif
 }
 

Marlin/endstop_interrupts.h

  */
 
 /**
- *  Endstop interrupts
- *  Without endstop interrups the stepper-ISR must always test all endstops when interested in their states (endstops.update()).
- *  Most time the test will result in finding out nothing has changed.
- *  With endstop interrupts endstops.update() is called only when we know that at least one endstop has changed its state.
+ * Endstop Interrupts
  *
- *  This can work only if all __used__ endstop pins can provide ether an 'external interrupt' or a 'pin change interrupt'.
- *  You can find out about pins issuing interrupts by running 'pin_interrupt_test.ino' (Marlin\buildroot\share\pin_interrupt_test\pin_interrupt_test.ino)
+ * Without endstop interrupts the endstop pins must be polled continually in
+ * the stepper-ISR via endstops.update(), most of the time finding no change.
+ * With this feature endstops.update() is called only when we know that at
+ * least one endstop has changed state, saving valuable CPU cycles.
+ *
+ * This feature only works when all used endstop pins can generate either an
+ * 'external interrupt' or a 'pin change interrupt'.
+ *
+ * Test whether pins issue interrupts on your board by flashing 'pin_interrupt_test.ino'.
+ * (Located in Marlin/buildroot/share/pin_interrupt_test/pin_interrupt_test.ino)
  */
 
  #ifndef _ENDSTOP_INTERRUPTS_H_
-   #define _ENDSTOP_INTERRUPTS_H_
-
-  /**
-   * Patch for pins_arduino.h (...\Arduino\hardware\arduino\avr\variants\mega\pins_arduino.h)  
-   *
-   * These macros for the Arduino MEGA do not include the two connected pins on Port J (D13, D14).
-   * So we extend them here because this are the normal pins for Y_MIN and Y_MAX on RAMPS.
-   * There are more PCI enabled processor pins on Port J, but they are not connected to Arduino MEGA.
-   */
-  #if defined(ARDUINO_AVR_MEGA2560) || defined(ARDUINO_AVR_MEGA)
-    #undef  digitalPinToPCICR
-    #define digitalPinToPCICR(p)    ( (((p) >= 10) && ((p) <= 15)) || \
-                                    (((p) >= 50) && ((p) <= 53)) || \
-                                    (((p) >= 62) && ((p) <= 69)) ? (&PCICR) : ((uint8_t *)0) )
-    #undef  digitalPinToPCICRbit
-    #define digitalPinToPCICRbit(p) ( (((p) >= 10) && ((p) <= 13)) || (((p) >= 50) && ((p) <= 53)) ? 0 : \
-                                    ( (((p) >= 14) && ((p) <= 15)) ? 1 : \
-                                    ( (((p) >= 62) && ((p) <= 69)) ? 2 : \
-                                    0 ) ) )
-    #undef  digitalPinToPCMSK
-    #define digitalPinToPCMSK(p)    ( (((p) >= 10) && ((p) <= 13)) || (((p) >= 50) && ((p) <= 53)) ? (&PCMSK0) : \
-                                    ( (((p) >= 14) && ((p) <= 15)) ? (&PCMSK1) : \
-                                    ( (((p) >= 62) && ((p) <= 69)) ? (&PCMSK2) : \
-                                    ((uint8_t *)0) ) ) )
-    #undef  digitalPinToPCMSKbit
-    #define digitalPinToPCMSKbit(p) ( (((p) >= 10) && ((p) <= 13)) ? ((p) - 6) : \
-                                    ( ((p) == 14) ? 2 : \
-                                    ( ((p) == 15) ? 1 : \
-                                    ( ((p) == 50) ? 3 : \
-                                    ( ((p) == 51) ? 2 : \
-                                    ( ((p) == 52) ? 1 : \
-                                    ( ((p) == 53) ? 0 : \
-                                    ( (((p) >= 62) && ((p) <= 69)) ? ((p) - 62) : \
-                                    0 ) ) ) ) ) ) ) )
-  #endif
-
-  volatile uint8_t e_hit = 0; // Different from 0 when the endstops shall be tested in detail. 
-                              // Must be reset to 0 by the test function when the tests are finished.
-
-  // Install Pin change interrupt for a pin, can be called multiple times
-  void pciSetup(byte pin) {
-    *digitalPinToPCMSK(pin) |= bit (digitalPinToPCMSKbit(pin));  // enable pin
-    PCIFR  |= bit (digitalPinToPCICRbit(pin)); // clear any outstanding interrupt
-    PCICR  |= bit (digitalPinToPCICRbit(pin)); // enable interrupt for the group
-  }
-
-  // This is what is really done inside the interrupts.
-  FORCE_INLINE void endstop_ISR_worker( void ) {
-    e_hit = 2; // Because the detection of a e-stop hit has a 1 step debouncer it has to be called at least twice.
-  }
-
-  // Use one Routine to handle each group
-  // One ISR for all EXT-Interrupts
-  void endstop_ISR(void) {
-    endstop_ISR_worker();
-  }
-
-  #ifdef PCINT0_vect
-    ISR(PCINT0_vect) { // handle pin change interrupt
-      endstop_ISR_worker();
-    }
-  #endif
-
-  #ifdef PCINT1_vect
-    ISR(PCINT1_vect) { // handle pin change interrupt
-      endstop_ISR_worker();
-    }
-  #endif
+ #define _ENDSTOP_INTERRUPTS_H_
 
-  #ifdef PCINT2_vect
-    ISR(PCINT2_vect) { // handle pin change interrupt
-      endstop_ISR_worker();
-    }
-  #endif
-
-  #ifdef PCINT3_vect
-    ISR(PCINT3_vect) { // handle pin change interrupt
-      endstop_ISR_worker();
-    }
-  #endif
-
-  void setup_enstop_interrupts( void ) {
-
-    #if HAS_X_MAX
-      #if (digitalPinToInterrupt(X_MAX_PIN) != NOT_AN_INTERRUPT) // if pin has an external interrupt
-        attachInterrupt(digitalPinToInterrupt(X_MAX_PIN), endstop_ISR, CHANGE); // assign it
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(X_MAX_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR"); // if pin has no pin change interrupt - error
-        pciSetup(X_MAX_PIN);                                                            // assign it
-      #endif
+/**
+ * Patch for pins_arduino.h (...\Arduino\hardware\arduino\avr\variants\mega\pins_arduino.h)
+ *
+ * These macros for the Arduino MEGA do not include the two connected pins on Port J (D13, D14).
+ * So we extend them here because these are the normal pins for Y_MIN and Y_MAX on RAMPS.
+ * There are more PCI-enabled processor pins on Port J, but they are not connected to Arduino MEGA.
+ */
+#if defined(ARDUINO_AVR_MEGA2560) || defined(ARDUINO_AVR_MEGA)
+  #undef  digitalPinToPCICR
+  #define digitalPinToPCICR(p)    ( (((p) >= 10) && ((p) <= 15)) || \
+                                  (((p) >= 50) && ((p) <= 53)) || \
+                                  (((p) >= 62) && ((p) <= 69)) ? (&PCICR) : ((uint8_t *)0) )
+  #undef  digitalPinToPCICRbit
+  #define digitalPinToPCICRbit(p) ( (((p) >= 10) && ((p) <= 13)) || (((p) >= 50) && ((p) <= 53)) ? 0 : \
+                                  ( (((p) >= 14) && ((p) <= 15)) ? 1 : \
+                                  ( (((p) >= 62) && ((p) <= 69)) ? 2 : \
+                                  0 ) ) )
+  #undef  digitalPinToPCMSK
+  #define digitalPinToPCMSK(p)    ( (((p) >= 10) && ((p) <= 13)) || (((p) >= 50) && ((p) <= 53)) ? (&PCMSK0) : \
+                                  ( (((p) >= 14) && ((p) <= 15)) ? (&PCMSK1) : \
+                                  ( (((p) >= 62) && ((p) <= 69)) ? (&PCMSK2) : \
+                                  ((uint8_t *)0) ) ) )
+  #undef  digitalPinToPCMSKbit
+  #define digitalPinToPCMSKbit(p) ( (((p) >= 10) && ((p) <= 13)) ? ((p) - 6) : \
+                                  ( ((p) == 14) ? 2 : \
+                                  ( ((p) == 15) ? 1 : \
+                                  ( ((p) == 50) ? 3 : \
+                                  ( ((p) == 51) ? 2 : \
+                                  ( ((p) == 52) ? 1 : \
+                                  ( ((p) == 53) ? 0 : \
+                                  ( (((p) >= 62) && ((p) <= 69)) ? ((p) - 62) : \
+                                  0 ) ) ) ) ) ) ) )
+#endif
+
+volatile uint8_t e_hit = 0; // Different from 0 when the endstops shall be tested in detail.
+                            // Must be reset to 0 by the test function when the tests are finished.
+
+// Install Pin change interrupt for a pin. Can be called multiple times.
+void pciSetup(byte pin) {
+  *digitalPinToPCMSK(pin) |= bit (digitalPinToPCMSKbit(pin));  // enable pin
+  PCIFR  |= bit (digitalPinToPCICRbit(pin)); // clear any outstanding interrupt
+  PCICR  |= bit (digitalPinToPCICRbit(pin)); // enable interrupt for the group
+}
+
+// This is what is really done inside the interrupts.
+FORCE_INLINE void endstop_ISR_worker( void ) {
+  e_hit = 2; // Because the detection of a e-stop hit has a 1 step debouncer it has to be called at least twice.
+}
+
+// Use one Routine to handle each group
+// One ISR for all EXT-Interrupts
+void endstop_ISR(void) { endstop_ISR_worker(); }
+
+// Handlers for pin change interrupts
+#ifdef PCINT0_vect
+  ISR(PCINT0_vect) { endstop_ISR_worker(); }
+#endif
+
+#ifdef PCINT1_vect
+  ISR(PCINT1_vect) { endstop_ISR_worker(); }
+#endif
+
+#ifdef PCINT2_vect
+  ISR(PCINT2_vect) { endstop_ISR_worker(); }
+#endif
+
+#ifdef PCINT3_vect
+  ISR(PCINT3_vect) { endstop_ISR_worker(); }
+#endif
+
+void setup_endstop_interrupts( void ) {
+
+  #if HAS_X_MAX
+    #if (digitalPinToInterrupt(X_MAX_PIN) != NOT_AN_INTERRUPT) // if pin has an external interrupt
+      attachInterrupt(digitalPinToInterrupt(X_MAX_PIN), endstop_ISR, CHANGE); // assign it
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(X_MAX_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR"); // if pin has no pin change interrupt - error
+      pciSetup(X_MAX_PIN);                                                            // assign it
     #endif
+  #endif
 
-    #if HAS_X_MIN
-      #if (digitalPinToInterrupt(X_MIN_PIN) != NOT_AN_INTERRUPT)
-        attachInterrupt(digitalPinToInterrupt(X_MIN_PIN), endstop_ISR, CHANGE);
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(X_MIN_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
-        pciSetup(X_MIN_PIN);
-      #endif
+  #if HAS_X_MIN
+    #if (digitalPinToInterrupt(X_MIN_PIN) != NOT_AN_INTERRUPT)
+      attachInterrupt(digitalPinToInterrupt(X_MIN_PIN), endstop_ISR, CHANGE);
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(X_MIN_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
+      pciSetup(X_MIN_PIN);
     #endif
+  #endif
 
-    #if HAS_Y_MAX
-      #if (digitalPinToInterrupt(Y_MAX_PIN) != NOT_AN_INTERRUPT)
-        attachInterrupt(digitalPinToInterrupt(Y_MAX_PIN), endstop_ISR, CHANGE);
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(Y_MAX_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
-        pciSetup(Y_MAX_PIN);
-      #endif
+  #if HAS_Y_MAX
+    #if (digitalPinToInterrupt(Y_MAX_PIN) != NOT_AN_INTERRUPT)
+      attachInterrupt(digitalPinToInterrupt(Y_MAX_PIN), endstop_ISR, CHANGE);
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(Y_MAX_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
+      pciSetup(Y_MAX_PIN);
     #endif
+  #endif
 
-    #if HAS_Y_MIN
-      #if (digitalPinToInterrupt(Y_MIN_PIN) != NOT_AN_INTERRUPT)
-        attachInterrupt(digitalPinToInterrupt(Y_MIN_PIN), endstop_ISR, CHANGE);
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(Y_MIN_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
-        pciSetup(Y_MIN_PIN);
-      #endif
+  #if HAS_Y_MIN
+    #if (digitalPinToInterrupt(Y_MIN_PIN) != NOT_AN_INTERRUPT)
+      attachInterrupt(digitalPinToInterrupt(Y_MIN_PIN), endstop_ISR, CHANGE);
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(Y_MIN_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
+      pciSetup(Y_MIN_PIN);
     #endif
+  #endif
 
-    #if HAS_Z_MAX
-      #if (digitalPinToInterrupt(Z_MAX_PIN) != NOT_AN_INTERRUPT)
-        attachInterrupt(digitalPinToInterrupt(Z_MAX_PIN), endstop_ISR, CHANGE);
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(Z_MAX_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
-        pciSetup(Z_MAX_PIN);
-      #endif
+  #if HAS_Z_MAX
+    #if (digitalPinToInterrupt(Z_MAX_PIN) != NOT_AN_INTERRUPT)
+      attachInterrupt(digitalPinToInterrupt(Z_MAX_PIN), endstop_ISR, CHANGE);
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(Z_MAX_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
+      pciSetup(Z_MAX_PIN);
     #endif
+  #endif
 
-    #if HAS_Z_MIN
-      #if (digitalPinToInterrupt(Z_MIN_PIN) != NOT_AN_INTERRUPT)
-        attachInterrupt(digitalPinToInterrupt(Z_MIN_PIN), endstop_ISR, CHANGE);
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(Z_MIN_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
-        pciSetup(Z_MIN_PIN);
-      #endif
+  #if HAS_Z_MIN
+    #if (digitalPinToInterrupt(Z_MIN_PIN) != NOT_AN_INTERRUPT)
+      attachInterrupt(digitalPinToInterrupt(Z_MIN_PIN), endstop_ISR, CHANGE);
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(Z_MIN_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
+      pciSetup(Z_MIN_PIN);
     #endif
+  #endif
 
-    #if HAS_Z2_MAX
-      #if (digitalPinToInterrupt(Z2_MAX_PIN) != NOT_AN_INTERRUPT)
-        attachInterrupt(digitalPinToInterrupt(Z2_MAX_PIN), endstop_ISR, CHANGE);
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(Z2_MAX_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
-        pciSetup(Z2_MAX_PIN);
-      #endif
+  #if HAS_Z2_MAX
+    #if (digitalPinToInterrupt(Z2_MAX_PIN) != NOT_AN_INTERRUPT)
+      attachInterrupt(digitalPinToInterrupt(Z2_MAX_PIN), endstop_ISR, CHANGE);
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(Z2_MAX_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
+      pciSetup(Z2_MAX_PIN);
     #endif
+  #endif
 
-    #if HAS_Z2_MIN
-      #if (digitalPinToInterrupt(Z2_MIN_PIN) != NOT_AN_INTERRUPT)
-        attachInterrupt(digitalPinToInterrupt(Z2_MIN_PIN), endstop_ISR, CHANGE);
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(Z2_MIN_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
-        pciSetup(Z2_MIN_PIN);
-      #endif
+  #if HAS_Z2_MIN
+    #if (digitalPinToInterrupt(Z2_MIN_PIN) != NOT_AN_INTERRUPT)
+      attachInterrupt(digitalPinToInterrupt(Z2_MIN_PIN), endstop_ISR, CHANGE);
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(Z2_MIN_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
+      pciSetup(Z2_MIN_PIN);
     #endif
+  #endif
 
-    #if HAS_Z_MIN_PROBE_PIN
-      #if (digitalPinToInterrupt(Z_MIN_PROBE_PIN) != NOT_AN_INTERRUPT)
-        attachInterrupt(digitalPinToInterrupt(Z_MIN_PROBE_PIN), endstop_ISR, CHANGE);
-      #else
-        // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
-        static_assert(digitalPinToPCICR(Z_MIN_PROBE_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
-        pciSetup(Z_MIN_PROBE_PIN);
-      #endif
+  #if HAS_Z_MIN_PROBE_PIN
+    #if (digitalPinToInterrupt(Z_MIN_PROBE_PIN) != NOT_AN_INTERRUPT)
+      attachInterrupt(digitalPinToInterrupt(Z_MIN_PROBE_PIN), endstop_ISR, CHANGE);
+    #else
+      // Not all used endstop/probe -pins can raise interrupts. Please deactivate ENDSTOP_INTERRUPTS or change the pin configuration!
+      static_assert(digitalPinToPCICR(Z_MIN_PROBE_PIN) != NULL, "ENDSTOP_INTERRUPT_ERROR");
+      pciSetup(Z_MIN_PROBE_PIN);
     #endif
+  #endif
 
-    // When we arive here without error each pin has ether a EXT-interrupt or a PCI.
-  }
-
+  // If we arrive here without raising an assertion, each pin has either an EXT-interrupt or a PCI.
+}
 
 #endif //_ENDSTOP_INTERRUPTS_H_

Marlin/example_configurations/Cartesio/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/Felix/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/Felix/DUAL/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/Hephestos/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/Hephestos_2/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/K8200/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/K8400/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/K8400/Dual-head/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/RepRapWorld/Megatronics/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/RigidBot/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/SCARA/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/TAZ4/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/WITBOX/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/adafruit/ST7565/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

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

 #define Z_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/delta/generic/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/delta/kossel_mini/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/delta/kossel_pro/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/delta/kossel_xl/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/makibox/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/example_configurations/tvrrug/Round2/Configuration.h

 #define Z_MAX_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 #define Z_MIN_PROBE_ENDSTOP_INVERTING true  // set to true to invert the logic of the endstop.
 
-// If all used endstop pins are able to cause interrupts, you can enable ENDSTOP_INTERRUPTS_FEATURE.
-// Then the function testing the endstops will only be called, if the state of one of the endstops changed.
+// Enable this feature if all enabled endstop pins are interrupt-capable.
+// This will remove the need to poll the interrupt pins, saving many CPU cycles.
 //#define ENDSTOP_INTERRUPTS_FEATURE
 
 //=============================================================================

Marlin/stepper.cpp

   }
 
   // Update endstops state, if enabled
-  if (endstops.enabled
+  if ((endstops.enabled
     #if HAS_BED_PROBE
       || endstops.z_probe_enabled
     #endif
-  )
-  #if ENABLED(ENDSTOP_INTERRUPTS_FEATURE)
-    if(e_hit) {
-  #endif
-      endstops.update();
-  #if ENABLED(ENDSTOP_INTERRUPTS_FEATURE)
+    )
+    #if ENABLED(ENDSTOP_INTERRUPTS_FEATURE)
+      && e_hit
+    #endif
+  ) {
+    endstops.update();
+
+    #if ENABLED(ENDSTOP_INTERRUPTS_FEATURE)
       e_hit--;
-    }
-  #endif
+    #endif
+  }
 
   // Take multiple steps per interrupt (For high speed moves)
   bool all_steps_done = false;