Add ==, != operators

Author: ecdr

DueTimer.h

@@ -71,6 +71,11 @@ class DueTimer
 
 	double getFrequency();
 	long getPeriod();
+
+  inline __attribute__((always_inline)) bool operator== (const DueTimer& rhs) const
+    {return timer == rhs.timer; };
+  inline __attribute__((always_inline)) bool operator!= (const DueTimer& rhs) const
+    {return timer != rhs.timer; };
 };
 
 // Just to call Timer.getAvailable instead of Timer::getAvailable() :
@@ -93,4 +98,4 @@ extern DueTimer Timer8;
 
 #else
 	#error Oops! Trying to include DueTimer on another device?
-#endif
+#endif

README.md

@@ -68,6 +68,12 @@ Timer.getAvailable().attachInterrupt(callback1).start(10);
 DueTimer::getAvailable().attachInterrupt(callback2).start(10);
 // Start timer on second available timer
 // And so on...
+
+DueTimer myTimer = Timer.getAvailable();
+if (myTimer != DueTimer(0))
+// Now we know that the timer returned is actually available
+// Can compare timers using == or !=
+
 ```
 
 ### Compatibility with Servo.h
@@ -104,7 +110,7 @@ You will need uncommend the line in `DueTimer.h` in `DueTimer` folder inside the
 
 ### You don't need to know:
 
-- `int timer` - Stores the object timer id (to acces Timers struct array).
+- `int timer` - Stores the object timer id (to access Timers struct array).
 
 - `DueTimer(int _timer)` - Instantiate a new DueTimer object for Timer _timer (NOTE: All objects are already instantiated!).