6 files changed, 7 insertions, 5 deletions
diff --git a/cores/arduino/Arduino.h b/cores/arduino/Arduino.h
index 5596c14..de1886d 100644
--- a/cores/arduino/Arduino.h
+++ b/cores/arduino/Arduino.h
@@ -151,6 +151,8 @@ extern const uint8_t PROGMEM digital_pin_to_timer_PGM[];
 #define NOT_A_PIN 0
 #define NOT_A_PORT 0
 
+#define NOT_AN_INTERRUPT -1
+
 #ifdef ARDUINO_MAIN
 #define PA 1
 #define PB 2
diff --git a/variants/leonardo/pins_arduino.h b/variants/leonardo/pins_arduino.h
index a0e1594..85fb06e 100644
--- a/variants/leonardo/pins_arduino.h
+++ b/variants/leonardo/pins_arduino.h
@@ -132,7 +132,7 @@ static const uint8_t A11 = 29;	// D12
 extern const uint8_t PROGMEM analog_pin_to_channel_PGM[];
 #define analogPinToChannel(P)  ( pgm_read_byte( analog_pin_to_channel_PGM + (P) ) )
 
-#define digitalPinToInterrupt(p) ((p) == 0 ? 2 : ((p) == 1 ? 3 : ((p) == 2 ? 1 : ((p) == 3 ? 0 : ((p) == 7 ? 4 : -1)))))
+#define digitalPinToInterrupt(p) ((p) == 0 ? 2 : ((p) == 1 ? 3 : ((p) == 2 ? 1 : ((p) == 3 ? 0 : ((p) == 7 ? 4 : NOT_AN_INTERRUPT)))))
 
 #ifdef ARDUINO_MAIN
 
diff --git a/variants/mega/pins_arduino.h b/variants/mega/pins_arduino.h
index 47151d4..f121889 100644
--- a/variants/mega/pins_arduino.h
+++ b/variants/mega/pins_arduino.h
@@ -83,7 +83,7 @@ static const uint8_t A15 = 69;
                                 ( (((p) >= 62) && ((p) <= 69)) ? ((p) - 62) : \
                                 0 ) ) ) ) ) )
 
-#define digitalPinToInterrupt(p) ((p) == 2 ? 0 : ((p) == 3 ? 1 : ((p) >= 18 && (p) <= 21 ? 23 - (p) : -1)))
+#define digitalPinToInterrupt(p) ((p) == 2 ? 0 : ((p) == 3 ? 1 : ((p) >= 18 && (p) <= 21 ? 23 - (p) : NOT_AN_INTERRUPT)))
 
 #ifdef ARDUINO_MAIN
 
diff --git a/variants/robot_control/pins_arduino.h b/variants/robot_control/pins_arduino.h
index f167896..979f3eb 100644
--- a/variants/robot_control/pins_arduino.h
+++ b/variants/robot_control/pins_arduino.h
@@ -94,7 +94,7 @@ static const uint8_t LED1	 = 17;  // D17 - RX_Led
 extern const uint8_t PROGMEM analog_pin_to_channel_PGM[];
 #define analogPinToChannel(P)  ( pgm_read_byte( analog_pin_to_channel_PGM + (P) ) )
 
-#define digitalPinToInterrupt(p) ((p) == 0 ? 2 : ((p) == 1 ? 3 : ((p) == 2 ? 1 : ((p) == 3 ? 0 : ((p) == 7 ? 4 : -1)))))
+#define digitalPinToInterrupt(p) ((p) == 0 ? 2 : ((p) == 1 ? 3 : ((p) == 2 ? 1 : ((p) == 3 ? 0 : ((p) == 7 ? 4 : NOT_AN_INTERRUPT)))))
 
 #ifdef ARDUINO_MAIN
 
diff --git a/variants/robot_motor/pins_arduino.h b/variants/robot_motor/pins_arduino.h
index cde2f3f..8179ac3 100644
--- a/variants/robot_motor/pins_arduino.h
+++ b/variants/robot_motor/pins_arduino.h
@@ -89,7 +89,7 @@ static const uint8_t TK4 = 12;   	// A11
 extern const uint8_t PROGMEM analog_pin_to_channel_PGM[];
 #define analogPinToChannel(P)  ( pgm_read_byte( analog_pin_to_channel_PGM + (P) ) )
 
-#define digitalPinToInterrupt(p) ((p) == 0 ? 2 : ((p) == 1 ? 3 : ((p) == 2 ? 1 : ((p) == 3 ? 0 : ((p) == 7 ? 4 : -1)))))
+#define digitalPinToInterrupt(p) ((p) == 0 ? 2 : ((p) == 1 ? 3 : ((p) == 2 ? 1 : ((p) == 3 ? 0 : ((p) == 7 ? 4 : NOT_AN_INTERRUPT)))))
 
 #ifdef ARDUINO_MAIN
 
diff --git a/variants/standard/pins_arduino.h b/variants/standard/pins_arduino.h
index 7923b03..e7cfb08 100644
--- a/variants/standard/pins_arduino.h
+++ b/variants/standard/pins_arduino.h
@@ -60,7 +60,7 @@ static const uint8_t A7 = 21;
 #define digitalPinToPCMSK(p)    (((p) <= 7) ? (&PCMSK2) : (((p) <= 13) ? (&PCMSK0) : (((p) <= 21) ? (&PCMSK1) : ((uint8_t *)0))))
 #define digitalPinToPCMSKbit(p) (((p) <= 7) ? (p) : (((p) <= 13) ? ((p) - 8) : ((p) - 14)))
 
-#define digitalPinToInterrupt(p)  ((p) == 2 ? 0 : ((p) == 3 ? 1 : -1))
+#define digitalPinToInterrupt(p)  ((p) == 2 ? 0 : ((p) == 3 ? 1 : NOT_AN_INTERRUPT))
 
 #ifdef ARDUINO_MAIN