基于STM32实现Modbus tcp Slave通信

【核心代码】

#define MB_TCP_TID          0
#define MB_TCP_PID          2
#define MB_TCP_LEN          4
#define MB_TCP_UID          6
#define MB_TCP_FUNC         7

#define MB_TCP_PROTOCOL_ID  0   /* 0 = Modbus Protocol */


/* ----------------------- Start implementation -----------------------------*/
eMBErrorCode
eMBTCPDoInit( USHORT ucTCPPort )
{
    eMBErrorCode    eStatus = MB_ENOERR;

    if( xMBTCPPortInit( ucTCPPort ) == FALSE )
    {
        eStatus = MB_EPORTERR;
    }
    return eStatus;
}

void
eMBTCPStart( void )
{
}

void
eMBTCPStop( void )
{
    /* Make sure that no more clients are connected. */
    vMBTCPPortDisable( );
}

eMBErrorCode
eMBTCPReceive( UCHAR * pucRcvAddress, UCHAR ** ppucFrame, USHORT * pusLength )
{
    eMBErrorCode    eStatus = MB_EIO;
    UCHAR          *pucMBTCPFrame;
    USHORT          usLength;
    USHORT          usPID;

    if( xMBTCPPortGetRequest( &pucMBTCPFrame, &usLength ) != FALSE )
    {
        usPID = pucMBTCPFrame[MB_TCP_PID] << 8U;
        usPID |= pucMBTCPFrame[MB_TCP_PID 1];

        if( usPID == MB_TCP_PROTOCOL_ID )
        {
            *ppucFrame = &pucMBTCPFrame[MB_TCP_FUNC];
            *pusLength = usLength - MB_TCP_FUNC;
            eStatus = MB_ENOERR;

            /* Modbus TCP does not use any addresses. Fake the source address such
             * that the processing part deals with this frame.
             */
            *pucRcvAddress = MB_TCP_PSEUDO_ADDRESS;
        }
    }
    else
    {
        eStatus = MB_EIO;
    }
    return eStatus;
}

eMBErrorCode
eMBTCPSend( UCHAR _unused, const UCHAR * pucFrame, USHORT usLength )
{
    eMBErrorCode    eStatus = MB_ENOERR;
    UCHAR          *pucMBTCPFrame = ( UCHAR * ) pucFrame - MB_TCP_FUNC;
    USHORT          usTCPLength = usLength MB_TCP_FUNC;

    /* The MBAP header is already initialized because the caller calls this
     * function with the buffer returned by the previous call. Therefore we 
     * only have to update the length in the header. Note that the length 
     * header includes the size of the Modbus PDU and the UID Byte. Therefore 
     * the length is usLength plus one.
     */
    pucMBTCPFrame[MB_TCP_LEN] = ( usLength 1 ) >> 8U;
    pucMBTCPFrame[MB_TCP_LEN 1] = ( usLength 1 ) & 0xFF;
    if( xMBTCPPortSendResponse( pucMBTCPFrame, usTCPLength ) == FALSE )
    {
        eStatus = MB_EIO;
    }
    return eStatus;
}

#endif