diff --git a/VARIANT_COMPLIANCE_CHANGELOG b/VARIANT_COMPLIANCE_CHANGELOG
new file mode 100644
index 000000000..bf1c2fe21
--- /dev/null
+++ b/VARIANT_COMPLIANCE_CHANGELOG
@@ -0,0 +1,8 @@
+SAMD CORE 1.6.6
+
+* digitalPinToInterrupt #define moved to Arduino.h, variant.h must no longer define it
+
+SAMD CORE 1.6.3
+
+* Timer for pin PWM selected based on value of PIN_ATTR_TIMER_ALT or PIN_ATTR_TIMER, 
+  prior to this pin type was used
diff --git a/cores/arduino/Arduino.h b/cores/arduino/Arduino.h
index 1be6d7171..3bafdb5fc 100644
--- a/cores/arduino/Arduino.h
+++ b/cores/arduino/Arduino.h
@@ -114,6 +114,11 @@ void loop( void ) ;
 
 #define bit(b) (1UL << (b))
 
+#if (ARDUINO_SAMD_VARIANT_COMPLIANCE >= 10606)
+// Interrupts
+#define digitalPinToInterrupt(P)   ( P )
+#endif
+
 // USB Device
 #include "USB/USBDesc.h"
 #include "USB/USBCore.h"
diff --git a/cores/arduino/WInterrupts.c b/cores/arduino/WInterrupts.c
index a1f1de9e2..70d9acd01 100644
--- a/cores/arduino/WInterrupts.c
+++ b/cores/arduino/WInterrupts.c
@@ -57,7 +57,11 @@ void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
   uint32_t config;
   uint32_t pos;
 
+#if ARDUINO_SAMD_VARIANT_COMPLIANCE >= 10606
+  EExt_Interrupts in = g_APinDescription[pin].ulExtInt;
+#else
   EExt_Interrupts in = digitalPinToInterrupt(pin);
+#endif
   if (in == NOT_AN_INTERRUPT || in == EXTERNAL_INT_NMI)
     return;
 
@@ -116,7 +120,11 @@ void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
  */
 void detachInterrupt(uint32_t pin)
 {
+#if (ARDUINO_SAMD_VARIANT_COMPLIANCE >= 10606)
+  EExt_Interrupts in = g_APinDescription[pin].ulExtInt;
+#else
   EExt_Interrupts in = digitalPinToInterrupt(pin);
+#endif 
   if (in == NOT_AN_INTERRUPT || in == EXTERNAL_INT_NMI)
     return;
 
diff --git a/variants/arduino_zero/variant.h b/variants/arduino_zero/variant.h
index 1a1d47565..cb88edb28 100644
--- a/variants/arduino_zero/variant.h
+++ b/variants/arduino_zero/variant.h
@@ -19,8 +19,8 @@
 #ifndef _VARIANT_ARDUINO_ZERO_
 #define _VARIANT_ARDUINO_ZERO_
 
-// The definitions here needs a SAMD core >=1.6.3
-#define ARDUINO_SAMD_VARIANT_COMPLIANCE 10603
+// The definitions here needs a SAMD core >=1.6.6
+#define ARDUINO_SAMD_VARIANT_COMPLIANCE 10606
 
 /*----------------------------------------------------------------------------
  *        Definitions
@@ -76,9 +76,6 @@ extern "C"
  */
 // #define digitalPinToTimer(P)
 
-// Interrupts
-#define digitalPinToInterrupt(P)   ( g_APinDescription[P].ulExtInt )
-
 // LEDs
 #define PIN_LED_13           (13u)
 #define PIN_LED_RXL          (25u)
diff --git a/variants/mkr1000/variant.h b/variants/mkr1000/variant.h
index 8a576f266..a6415d599 100644
--- a/variants/mkr1000/variant.h
+++ b/variants/mkr1000/variant.h
@@ -18,8 +18,8 @@
 
 #pragma once
 
-// The definitions here needs a SAMD core >=1.6.3
-#define ARDUINO_SAMD_VARIANT_COMPLIANCE 10603
+// The definitions here needs a SAMD core >=1.6.6
+#define ARDUINO_SAMD_VARIANT_COMPLIANCE 10606
 
 #include <WVariant.h>
 
@@ -51,7 +51,6 @@
 #define portInputRegister(port)  (&(port->IN.reg))
 #define portModeRegister(port)   (&(port->DIR.reg))
 #define digitalPinHasPWM(P)      (g_APinDescription[P].ulPWMChannel != NOT_ON_PWM || g_APinDescription[P].ulTCChannel != NOT_ON_TIMER)
-#define digitalPinToInterrupt(P) (g_APinDescription[P].ulExtInt)
 
 /*
  * digitalPinToTimer(..) is AVR-specific and is not defined for SAMD