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.

Revision:
3:4cda95d7b6c5
Parent:
0:0453a0a7e500
--- a/mbport.h	Tue Dec 03 09:13:22 2019 +0000
+++ b/mbport.h	Mon Jan 06 01:17:26 2020 +0000
@@ -110,6 +110,12 @@
 
 extern          BOOL( *pxMBPortCBTimerExpired ) ( void );
 
+/* ----------------------- RTU custom port functions -------------------------------*/
+
+BOOL            xMBRTUCustGetPDU( UCHAR **ppucMBRTUFrame, USHORT * usRTULength );
+
+BOOL            xMBRTUCustSendResponse( const UCHAR *pucMBRTUFrame, USHORT usRTULength );
+
 /* ----------------------- TCP port functions -------------------------------*/
 BOOL            xMBTCPPortInit( USHORT usTCPPort );
 
@@ -124,4 +130,4 @@
 #ifdef __cplusplus
 PR_END_EXTERN_C
 #endif
-#endif
+#endif
\ No newline at end of file