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support conditional ignore of Modbus broadcast frames #27

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support conditional ignore of Modbus broadcast frames #27

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14 changes: 14 additions & 0 deletions modbus/include/mb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -410,6 +410,20 @@ eMBErrorCode eMBRegCoilsCB( UCHAR * pucRegBuffer, USHORT usAddress,
eMBErrorCode eMBRegDiscreteCB( UCHAR * pucRegBuffer, USHORT usAddress,
USHORT usNDiscrete );

/*! \defgroup protocol_mgmt Protocol management
* \code #include "mb.h" \endcode
*/

/*! \brief Callback determining if a broadcast frame should be responded to.
*
* The callback is evaluated once for each incoming Modbus broadcast frame.
* See the <em>MB_SUPPORT_IGNORE_BROADCAST</em>
* configuration macro on how to enable the callback.
*
* \return non-zero to ignore the broadcast frame, zero otherwise.
*/
UCHAR xMBIgnoreBroadcast( void );

#ifdef __cplusplus
PR_END_EXTERN_C
#endif
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13 changes: 13 additions & 0 deletions modbus/include/mbconfig.h
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,19 @@ PR_BEGIN_EXTERN_C
#define MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS ( 0 )
#endif

/*! \brief If <em>xMBIgnoreBroadcast</em> should be supported.
*
* Defaults to zero, meaning freemodbus
* behaves classically (always responds to broadcast).
*
* If you enable this, you must implement the mentioned callback function.
* Since this is just a default, you can define the macro externally,
* and avoid modifications to this file.
*/
#ifndef MB_SUPPORT_IGNORE_BROADCAST
#define MB_SUPPORT_IGNORE_BROADCAST ( 0 )
#endif

/*! \brief Maximum number of Modbus functions codes the protocol stack
* should support.
*
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6 changes: 5 additions & 1 deletion modbus/mb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -360,7 +360,11 @@ eMBPoll( void )
if( eStatus == MB_ENOERR )
{
/* Check if the frame is for us. If not ignore the frame. */
#if MB_SUPPORT_IGNORE_BROADCAST > 0
if( ( ucRcvAddress == ucMBAddress ) || ( ( ucRcvAddress == MB_ADDRESS_BROADCAST ) && !xMBIgnoreBroadcast() ) )
#else
if( ( ucRcvAddress == ucMBAddress ) || ( ucRcvAddress == MB_ADDRESS_BROADCAST ) )
#endif
{
( void )xMBPortEventPost( EV_EXECUTE );
}
Expand Down Expand Up @@ -398,7 +402,7 @@ eMBPoll( void )
if( ( eMBCurrentMode == MB_ASCII ) && MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS )
{
vMBPortTimersDelay( MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS );
}
}
eStatus = peMBFrameSendCur( ucMBAddress, ucMBFrame, usLength );
}
break;
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