Added attachable ISR.

This is not strictly required for a wake alarm
as the IRQ routine will wake the board.

Author: GabrielNotman

src/RTCZero.cpp

@@ -21,6 +21,8 @@
 
 static bool __time24 = false;
 
+voidFuncPtr RTC_callBack = NULL;
+
 void RTCZero::begin(bool timeRep) 
 {
   uint16_t tmp_reg = 0;
@@ -76,6 +78,10 @@ void RTCZero::begin(bool timeRep)
 
 void RTC_Handler(void)
 {
+  if (RTC_callBack != NULL) {
+    RTC_callBack();
+  }
+
   RTC->MODE2.INTFLAG.reg = RTC_MODE2_INTFLAG_ALARM0; // must clear flag at end
 }
 
@@ -93,6 +99,16 @@ void RTCZero::disableAlarm()
     ;
 }
 
+void RTCZero::attachInterrupt(voidFuncPtr callback)
+{
+  RTC_callBack = callback;
+}
+
+void RTCZero::detachInterrupt()
+{
+  RTC_callBack = NULL;
+}
+
 /*
  * Get Functions
  */

src/RTCZero.h

@@ -24,6 +24,8 @@
 
 #include "Arduino.h"
 
+typedef void(*voidFuncPtr)(void);
+
 class RTCZero {
 public:
 
@@ -43,6 +45,9 @@ class RTCZero {
 
   void enableAlarm(Alarm_Match match);
   void disableAlarm();
+
+  void attachInterrupt(voidFuncPtr callback);
+  void detachInterrupt();
 
   /* Get Functions */