Fix build on mega2560

speeduino/board_avr2560.cpp

@@ -1,5 +1,6 @@
 #include "globals.h"
 #if defined(CORE_AVR)
+#include "board_avr2560.h"
 #include "auxiliaries.h"
 #include "comms_secondary.h"
 
@@ -23,7 +24,9 @@ void initBoard(void)
     * General
     */
     configPage9.intcan_available = 0;   // AVR devices do NOT have internal canbus
-    pSecondarySerial = &Serial3;
+    #ifdef secondarySerial_AVAILABLE
+      pSecondarySerial = &Serial3;
+    #endif
 
     /*
     ***********************************************************************************************************

speeduino/board_avr2560.h

@@ -158,10 +158,10 @@ static inline void IGN8_TIMER_DISABLE(void) { TIMSK3 &= ~(1 << OCIE3B); } //Repl
 ***********************************************************************************************************
 * CAN / Second serial
 */
-
+#if ( defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__) )
   #define secondarySerial_AVAILABLE
-  #define SECONDARY_SERIAL_T HardwareSerial
-
+#endif
+#define SECONDARY_SERIAL_T HardwareSerial
 
 #endif //CORE_AVR
 #endif //AVR2560_H