Powerup radio if asleep when start transmitting.

RF24.cpp

@@ -677,6 +677,9 @@ void RF24::startFastWrite( const void* buf, uint8_t len, const bool multicast){
 //Allows the library to pass all tests
 void RF24::startWrite( const void* buf, uint8_t len, const bool multicast ){
 
+	// Powerup radio if not already alive.
+	powerUp();
+
   // Send the payload
 
   //write_payload( buf, len );