Daniel McKinnell
Forking https://os.mbed.com/users/cam/code/Modbus/ to work for NUCLEO 64 boards
Fork of Cam's original FreeModbus port (https://os.mbed.com/users/cam/code/Modbus/)
Change: - Serial implementation to work for NUCLEO 64 boards and receive interrupts instead of timer. (see `portserial.cpp`)
Added: - Custom RTU mode. Allows for external implementation of packet receiving and sending. Sends and receives packets as whole frames (address + PDU) (i.e. this was added for a custom LoRa implementation). implement `xMBRTUCustGetPDU` and `xMBRTUCustSendResponse` (see `mbport.h`) and call `eMBRTUCustomInit( address )`. implementations need to be fully initialised as `eMBRTUCustomInit` only sets the address and nothing else.