diff --git a/ChangeLog.md b/ChangeLog.md
index 42293d94..d70b6c83 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -35,10 +35,11 @@ Changes listed here are checked in to GitHub ("master" branch unless specificall
 * Maintenance: Rebuild all bootloader files.
 * Bugfix: The recently introduced entry condition functionality of Optiboot was busted.
 * Maintenance: Rebuild all bootloader files again.
-* Enhancement (contributed): Merge in support for using XDIR and RS485 (custom optiboot build only).
-* Enhancement: Add a test to the start of twi_pins.h that will allows it to be carried to another modern AVR core that doesn't provide badArg and badCall. Add CORE_HAS_ERRORFUNS #define.
 * Bugfix: Correct issue with missing getAnalogReadResolution function body.
 * Maintenance: Work around CLI regression by specifying cli 0.33.0 for the CI.
+* Enhancement (contributed): Merge in support for using XDIR and RS485 (custom optiboot build only).
+* Enhancement: Add a test to the start of twi_pins.h that will allows it to be carried to another modern AVR core that doesn't provide badArg and badCall. Add CORE_HAS_ERRORFUNS #define.
+* Enhancement: Add `_digitalPinToCanon()` to convert pin numbers to `(port * 8) + bit_position`, will be needed to address recently reported shortcomings of the SPI library surrounding interrupts.
 
 ### 2.6.8
 * CRITICAL bugfix: Fix issues introduced by pwm option menu. This prevented compilation on 1-series or Microchip boards. There were at least *4 separate issues* feeding into this.
diff --git a/megaavr/cores/megatinycore/Arduino.h b/megaavr/cores/megatinycore/Arduino.h
index 82008e28..54f0d679 100644
--- a/megaavr/cores/megatinycore/Arduino.h
+++ b/megaavr/cores/megatinycore/Arduino.h
@@ -723,6 +723,31 @@ See Ref_Analog.md for more information of the representations of "analog pins".
   uint8_t _setRTCEventChan(uint8_t vail, uint8_t chan); // number is 0, 1 or 255 like above, div is log(2) of the divisor (ie, for 2^5, his would be 5).
   uint8_t _getRTCEventConfig(); //simply returns the RTC channel configuration. Will likely return 255 if called on non Ex
   uint8_t _RTCPrescaleToVal(uint16_t prescale)
+#endif
+  /* The Variant file must do one of the following */
+/* 1. Use the same pin order as this core's default pin mapping (recommended)
+ * 2. Number each pin (port * 8) + bit_position, and define HYPERRATIONAL_PIN_NUMBERS (also recommended)
+ * 3. Number each pin (port * 8) + bit_position + 1, with PA0 wrapping around to the highest number and define RATIONALPLUS_PIN_NUMBERS
+ * 4. Define SPECIAL_PIN_NUMBERS, and use any pin numbering. (recommended if you must use a layout that departs significantly from the above)
+ */
+
+#if defined(HYPERRATIONAL_PIN_NUMBERS) /* Pins numbered starting from PA0, and PB6 and PB7 (14, 15) skipped on 20-pin */
+  #define _digitalPinToCanon(pin) (((pin) < NUM_TOTAL_PINS) ? (pin) : NOT_A_PIN)
+#elif defined(RATIONALPLUS_PIN_NUMBERS) /* Pins numbered starting from PA1 = 0, so pin + 1 = cannonical pin number */
+  #define _digitalPinToCanon(pin) (((pin) < NUM_TOTAL_PINS) ? (((pin) == NUM_TOTAL_PINS - 1) ? 0 :((pin) + 1 ))  : NOT_A_PIN)
+#elif defined(SPECIAL_PIN_NUMBERS)
+  #define _digitalPinToCanon(pin) (((pin) < NUM_TOTAL_PINS) ? ((digital_pin_to_port[pin] << 3) + digital_pin_to_bit_position[pin] ) : NOT_A_PIN)
+#else
+  #if _AVR_PINCOUNT == 8
+    const uint8_t _dptc[] = {6,7,1,2,3,0};
+    #define _digitalPinToCanon(pin) (((pin) < NUM_TOTAL_PINS) ? (_dptc[(pin)]) : NOT_A_PIN)
+  #elif _AVR_PINCOUNT == 14
+    #define _digitalPinToCanon(pin) (((pin) < NUM_TOTAL_PINS) ? (((pin) < PIN_PA1) ? ((((pin) > PIN_PA7 && (pin) < PIN_PC0) ? 15 - (pin) : (pin) + 4)) : (((pin) == 11) ? 0 : (pin) - 7)) : NOT_A_PIN)
+  #elif _AVR_PINCOUNT == 20
+    #define _digitalPinToCanon(pin) (((pin) < NUM_TOTAL_PINS) ? (((pin) < PIN_PA1) ? ((((pin) > PIN_PA7 && (pin) < PIN_PC0) ? 17 - (pin) : (pin) + 4)) : (((pin) == 17) ? 0 : (pin) - 13)) : NOT_A_PIN)
+  #else /* 24 pins */
+    #define _digitalPinToCanon(pin) (((pin) < NUM_TOTAL_PINS) ? (((pin) < PIN_PA1) ? ((((pin) > PIN_PA7 && (pin) < PIN_PC0) ? 19 - (pin) : (pin) + 4)) : (((pin) == 21) ? 0 : (pin) - 17)) : NOT_A_PIN)
+  #endif
 #endif
 #ifdef __cplusplus
 } // extern "C"
diff --git a/megaavr/cores/megatinycore/core_parameters.h b/megaavr/cores/megatinycore/core_parameters.h
index 31abc750..8e888308 100644
--- a/megaavr/cores/megatinycore/core_parameters.h
+++ b/megaavr/cores/megatinycore/core_parameters.h
@@ -82,6 +82,5 @@
 #if defined(UARTBAUD5V) || defined(UARTBAUD3V)
   #warning "The UARTBAUDxV baud rate correction was removed in 2.3.0 because it had excessive overhead and negligible benefit. The define you specified does nothing."
 #endif
-#endif
 
 #endif