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:
0:0453a0a7e500
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbproto.h	Thu Apr 15 12:10:34 2010 +0000
@@ -0,0 +1,83 @@
+/* 
+ * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
+ * Copyright (c) 2006 Christian Walter <wolti@sil.at>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * File: $Id: mbproto.h,v 1.14 2006/12/07 22:10:34 wolti Exp $
+ */
+
+#ifndef _MB_PROTO_H
+#define _MB_PROTO_H
+
+#ifdef __cplusplus
+PR_BEGIN_EXTERN_C
+#endif
+/* ----------------------- Defines ------------------------------------------*/
+#define MB_ADDRESS_BROADCAST    ( 0 )   /*! Modbus broadcast address. */
+#define MB_ADDRESS_MIN          ( 1 )   /*! Smallest possible slave address. */
+#define MB_ADDRESS_MAX          ( 247 ) /*! Biggest possible slave address. */
+#define MB_FUNC_NONE                          (  0 )
+#define MB_FUNC_READ_COILS                    (  1 )
+#define MB_FUNC_READ_DISCRETE_INPUTS          (  2 )
+#define MB_FUNC_WRITE_SINGLE_COIL             (  5 )
+#define MB_FUNC_WRITE_MULTIPLE_COILS          ( 15 )
+#define MB_FUNC_READ_HOLDING_REGISTER         (  3 )
+#define MB_FUNC_READ_INPUT_REGISTER           (  4 )
+#define MB_FUNC_WRITE_REGISTER                (  6 )
+#define MB_FUNC_WRITE_MULTIPLE_REGISTERS      ( 16 )
+#define MB_FUNC_READWRITE_MULTIPLE_REGISTERS  ( 23 )
+#define MB_FUNC_DIAG_READ_EXCEPTION           (  7 )
+#define MB_FUNC_DIAG_DIAGNOSTIC               (  8 )
+#define MB_FUNC_DIAG_GET_COM_EVENT_CNT        ( 11 )
+#define MB_FUNC_DIAG_GET_COM_EVENT_LOG        ( 12 )
+#define MB_FUNC_OTHER_REPORT_SLAVEID          ( 17 )
+#define MB_FUNC_ERROR                         ( 128 )
+/* ----------------------- Type definitions ---------------------------------*/
+    typedef enum
+{
+    MB_EX_NONE = 0x00,
+    MB_EX_ILLEGAL_FUNCTION = 0x01,
+    MB_EX_ILLEGAL_DATA_ADDRESS = 0x02,
+    MB_EX_ILLEGAL_DATA_VALUE = 0x03,
+    MB_EX_SLAVE_DEVICE_FAILURE = 0x04,
+    MB_EX_ACKNOWLEDGE = 0x05,
+    MB_EX_SLAVE_BUSY = 0x06,
+    MB_EX_MEMORY_PARITY_ERROR = 0x08,
+    MB_EX_GATEWAY_PATH_FAILED = 0x0A,
+    MB_EX_GATEWAY_TGT_FAILED = 0x0B
+} eMBException;
+
+typedef         eMBException( *pxMBFunctionHandler ) ( UCHAR * pucFrame, USHORT * pusLength );
+
+typedef struct
+{
+    UCHAR           ucFunctionCode;
+    pxMBFunctionHandler pxHandler;
+} xMBFunctionHandler;
+
+#ifdef __cplusplus
+PR_END_EXTERN_C
+#endif
+#endif