Tooltron

 /*

  * FreeRTOS Modbus Libary: A Modbus serial implementation for FreeRTOS

  * Copyright (C) 2006 Christian Walter <wolti@sil.at>

  *

  * This library is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public

  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *

  * This library is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

  * Lesser General Public License for more details.

  *

  * You should have received a copy of the GNU Lesser General Public

  * License along with this library; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

  */

/* ----------------------- System includes ----------------------------------*/

#include "stdlib.h"

#include "string.h"

/* ----------------------- Platform includes --------------------------------*/

#include "port.h"

/* ----------------------- Modbus includes ----------------------------------*/

#include "mb.h"

#include "mbframe.h"

#include "mbproto.h"

#include "mbconfig.h"

/* ----------------------- Defines ------------------------------------------*/

#define MB_PDU_FUNC_READ_ADDR_OFF           ( MB_PDU_DATA_OFF )

#define MB_PDU_FUNC_READ_DISCCNT_OFF        ( MB_PDU_DATA_OFF + 2 )

#define MB_PDU_FUNC_READ_SIZE               ( 4 )

#define MB_PDU_FUNC_READ_DISCCNT_MAX        ( 0x07D0 )

/* ----------------------- Static functions ---------------------------------*/

eMBException    prveMBError2Exception( eMBErrorCode eErrorCode );

/* ----------------------- Start implementation -----------------------------*/

#if MB_FUNC_READ_COILS_ENABLED > 0

eMBException

eMBFuncReadDiscreteInputs( UCHAR * pucFrame, USHORT * usLen )

{

    USHORT          usRegAddress;

    USHORT          usDiscreteCnt;

    UCHAR           ucNBytes;

    UCHAR          *pucFrameCur;

    eMBException    eStatus = MB_EX_NONE;

    eMBErrorCode    eRegStatus;

    if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )

    {

        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );

        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );

        usRegAddress++;

        usDiscreteCnt = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF] << 8 );

        usDiscreteCnt |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF + 1] );

        /* Check if the number of registers to read is valid. If not

         * return Modbus illegal data value exception. 

         */

        if( ( usDiscreteCnt >= 1 ) &&

            ( usDiscreteCnt < MB_PDU_FUNC_READ_DISCCNT_MAX ) )

        {

            /* Set the current PDU data pointer to the beginning. */

            pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];

            *usLen = MB_PDU_FUNC_OFF;

            /* First byte contains the function code. */

            *pucFrameCur++ = MB_FUNC_READ_DISCRETE_INPUTS;

            *usLen += 1;

            /* Test if the quantity of coils is a multiple of 8. If not last

             * byte is only partially field with unused coils set to zero. */

            if( ( usDiscreteCnt & 0x0007 ) != 0 )

            {

                ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 + 1 );

            }

            else

            {

                ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 );

            }

            *pucFrameCur++ = ucNBytes;

            *usLen += 1;

            eRegStatus =

                eMBRegDiscreteCB( pucFrameCur, usRegAddress, usDiscreteCnt );

            /* If an error occured convert it into a Modbus exception. */

            if( eRegStatus != MB_ENOERR )

            {

                eStatus = prveMBError2Exception( eRegStatus );

            }

            else

            {

                /* The response contains the function code, the starting address

                 * and the quantity of registers. We reuse the old values in the 

                 * buffer because they are still valid. */

                *usLen += ucNBytes;;

            }

        }

        else

        {

            eStatus = MB_EX_ILLEGAL_DATA_VALUE;

        }

    }

    else

    {

        /* Can't be a valid read coil register request because the length

         * is incorrect. */

        eStatus = MB_EX_ILLEGAL_DATA_VALUE;

    }

    return eStatus;

}

#endif