mbascii.c

modbus开发程序包

            eBytePos = BYTE_HIGH_NIBBLE;
            usRcvBufferPos = 0;
        }
        else if( ucByte == MB_ASCII_DEFAULT_CR )
        {
            eRcvState = STATE_RX_WAIT_EOF;
        }
        else
        {
            ucResult = prvucMBCHAR2BIN( ucByte );
            switch ( eBytePos )
            {
                /* High nibble of the byte comes first. We check for
                 * a buffer overflow here. */
            case BYTE_HIGH_NIBBLE:
                if( usRcvBufferPos < MB_SER_PDU_SIZE_MAX )
                {
                    ucASCIIBuf[usRcvBufferPos] = ( UCHAR )( ucResult << 4 );
                    eBytePos = BYTE_LOW_NIBBLE;
                    break;
                }
                else
                {
                    /* not handled in Modbus specification but seems
                     * a resonable implementation. */
                    eRcvState = STATE_RX_IDLE;
                    /* Disable previously activated timer because of error state. */
                    vMBPortTimersDisable(  );
                }
                break;

            case BYTE_LOW_NIBBLE:
                ucASCIIBuf[usRcvBufferPos++] |= ucResult;
                eBytePos = BYTE_HIGH_NIBBLE;
                break;
            }
        }
        break;

    case STATE_RX_WAIT_EOF:
        if( ucByte == ucMBLFCharacter )
        {
            /* Disable character timeout timer because all characters are
             * received. */
            vMBPortTimersDisable(  );
            /* Receiver is again in idle state. */
            eRcvState = STATE_RX_IDLE;

            /* Notify the caller of eMBASCIIReceive that a new frame
             * was received. */
            xNeedPoll = xMBPortEventPost( EV_FRAME_RECEIVED );
        }
        else if( ucByte == ':' )
        {
            /* Empty receive buffer and back to receive state. */
            eBytePos = BYTE_HIGH_NIBBLE;
            usRcvBufferPos = 0;
            eRcvState = STATE_RX_RCV;

            /* Enable timer for character timeout. */
            vMBPortTimersEnable(  );
        }
        else
        {
            /* Frame is not okay. Delete entire frame. */
            eRcvState = STATE_RX_IDLE;
        }
        break;

    case STATE_RX_IDLE:
        if( ucByte == ':' )
        {
            /* Enable timer for character timeout. */
            vMBPortTimersEnable(  );
            /* Reset the input buffers to store the frame. */
            usRcvBufferPos = 0;;
            eBytePos = BYTE_HIGH_NIBBLE;
            eRcvState = STATE_RX_RCV;
        }
        break;
    }

    return xNeedPoll;
}

BOOL
xMBASCIITransmitFSM( void )
{
    BOOL            xNeedPoll = FALSE;
    UCHAR           ucByte;

    assert( eRcvState == STATE_RX_IDLE );
    switch ( eSndState )
    {
        /* Start of transmission. The start of a frame is defined by sending
         * the character ':'. */
    case STATE_TX_START:
        ucByte = ':';
        xMBPortSerialPutByte( ( CHAR )ucByte );
        eSndState = STATE_TX_DATA;
        eBytePos = BYTE_HIGH_NIBBLE;
        break;

        /* Send the data block. Each data byte is encoded as a character hex
         * stream with the high nibble sent first and the low nibble sent
         * last. If all data bytes are exhausted we send a '\r' character
         * to end the transmission. */
    case STATE_TX_DATA:
        if( usSndBufferCount > 0 )
        {
            switch ( eBytePos )
            {
            case BYTE_HIGH_NIBBLE:
                ucByte = prvucMBBIN2CHAR( ( UCHAR )( *pucSndBufferCur >> 4 ) );
                xMBPortSerialPutByte( ( CHAR ) ucByte );
                eBytePos = BYTE_LOW_NIBBLE;
                break;

            case BYTE_LOW_NIBBLE:
                ucByte = prvucMBBIN2CHAR( ( UCHAR )( *pucSndBufferCur & 0x0F ) );
                xMBPortSerialPutByte( ( CHAR )ucByte );
                pucSndBufferCur++;
                eBytePos = BYTE_HIGH_NIBBLE;
                usSndBufferCount--;
                break;
            }
        }
        else
        {
            xMBPortSerialPutByte( MB_ASCII_DEFAULT_CR );
            eSndState = STATE_TX_END;
        }
        break;

        /* Finish the frame by sending a LF character. */
    case STATE_TX_END:
        xMBPortSerialPutByte( ( CHAR )ucMBLFCharacter );
        /* We need another state to make sure that the CR character has
         * been sent. */
        eSndState = STATE_TX_NOTIFY;
        break;

        /* Notify the task which called eMBASCIISend that the frame has
         * been sent. */
    case STATE_TX_NOTIFY:
        eSndState = STATE_TX_IDLE;
        xNeedPoll = xMBPortEventPost( EV_FRAME_SENT );

        /* Disable transmitter. This prevents another transmit buffer
         * empty interrupt. */
        vMBPortSerialEnable( TRUE, FALSE );
        eSndState = STATE_TX_IDLE;
        break;

        /* We should not get a transmitter event if the transmitter is in
         * idle state.  */
    case STATE_TX_IDLE:
        /* enable receiver/disable transmitter. */
        vMBPortSerialEnable( TRUE, FALSE );
        break;
    }

    return xNeedPoll;
}

BOOL
xMBASCIITimerT1SExpired( void )
{
    switch ( eRcvState )
    {
        /* If we have a timeout we go back to the idle state and wait for
         * the next frame.
         */
    case STATE_RX_RCV:
    case STATE_RX_WAIT_EOF:
        eRcvState = STATE_RX_IDLE;
        break;

    default:
        assert( ( eRcvState == STATE_RX_RCV ) || ( eRcvState == STATE_RX_WAIT_EOF ) );
        break;
    }
    vMBPortTimersDisable(  );

    /* no context switch required. */
    return FALSE;
}


static          UCHAR
prvucMBCHAR2BIN( UCHAR ucCharacter )
{
    if( ( ucCharacter >= '0' ) && ( ucCharacter <= '9' ) )
    {
        return ( UCHAR )( ucCharacter - '0' );
    }
    else if( ( ucCharacter >= 'A' ) && ( ucCharacter <= 'F' ) )
    {
        return ( UCHAR )( ucCharacter - 'A' + 0x0A );
    }
    else
    {
        return 0xFF;
    }
}

static          UCHAR
prvucMBBIN2CHAR( UCHAR ucByte )
{
    if( ucByte <= 0x09 )
    {
        return ( UCHAR )( '0' + ucByte );
    }
    else if( ( ucByte >= 0x0A ) && ( ucByte <= 0x0F ) )
    {
        return ( UCHAR )( ucByte - 0x0A + 'A' );
    }
    else
    {
        /* Programming error. */
        assert( 0 );
    }
    return '0';
}


static          UCHAR
prvucMBLRC( UCHAR * pucFrame, USHORT usLen )
{
    UCHAR           ucLRC = 0;  /* LRC char initialized */

    while( usLen-- )
    {
        ucLRC += *pucFrame++;   /* Add buffer byte without carry */
    }

    /* Return twos complement */
    ucLRC = ( UCHAR ) ( -( ( CHAR ) ucLRC ) );
    return ucLRC;
}

#endif