Compared to V2.3 the default timer used in combination with AtMega 2560 (as well as 640, 1280, 1281 and 2561) processors is changed from Timer 5 into Timer 3. In addition, it is possible to change the default Timer 3 into Timer 4 or 5. To make such change, modify the file RSbusVariants.h and uncomment the line with #define RSBUS_USES_SW_T4 or #define RSBUS_USES_SW_T5.