A modest proposal - expose the interrupt so a user can write a callback function.

[TheDougMiester]

First let me say I love your work - this library saved the day for me. That said, I'd like to propose a very minor improvement. I'm not the sort of guy who just complains about something without offering a solution, so I've attached one. Here's the deal:

I recently had program which had a ton of "delay" calls in it. Sad, but necessary for reasons I don't think are worth going into. The result was "loop()" wasn't very timely in catching and processing calls to "if (mySwitch.available())". So, I needed to get access to RCSwitch's handleInterrupt call. It works pretty well, so I'd like to propose it as a new feature to an already excellent library. I'll attach the files, but here's the gist of it:

1. In RCSwitch, just below the other enableReceive() declarations, add one more (line 86):
   void enableReceive(int interrupt, void (*ptrToFunction)(void));

2. In RCSwitch.h at around line 158, make the following changes (lines 162 and 163 are new, the rest is already there):
   #if not defined( RCSwitchDisableReceiving )
   static void handleInterrupt();
   static bool receiveProtocol(const int p, unsigned int changeCount);
   int nReceiverInterrupt;
   static bool functionPtrExists; //NEW LINE
   static void (*externalFunctionPtr)(void); //NEW LINE
   #endif

3. In RCSwitch.cpp, change the declaration of RCSwitch:RCSwitch() to read as follows:
   RCSwitch::RCSwitch() {
   this->nTransmitterPin = -1;
   this->setRepeatTransmit(10);
   this->setProtocol(1);
   #if not defined( RCSwitchDisableReceiving )
   this->nReceiverInterrupt = -1;
   this->setReceiveTolerance(60);
   RCSwitch::nReceivedValue = 0;
   this->externalFunctionPtr = NULL; //NEW
   this->functionPtrExists = false; //NEW
   #endif
   }

4. Then in RCSwitch.cpp, add the code for the new enableReceive defined in the header file:
   void RCSwitch::enableReceive(int interrupt, void (*ptrToFunction)(void)){
   externalFunctionPtr = ptrToFunction;
   functionPtrExists = true;
   this->enableReceive(interrupt); //call to existing enableReceive
   }

5. Finally, add the following 3 lines to the bottom of RECEIVE_ATTR RCSwitch::handleInterrupt() :
   if(functionPtrExists == true) {
   externalFunctionPtr();
   }

Once you have done all this, in your main file for your arduino code, you would declare your function:
void foo() {
//do stuff
}

this would get called in your code by: myRcSwitch.enable(0, &foo);

I've attached the proposed changes. Feel free to use them or not. Again, thanks for the great library
RCSwitch-with-proposed-interrupt-mods-(and-test-code).zip