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 /*
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  * FreeRTOS Modbus Libary: A Modbus serial implementation for FreeRTOS
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  * Copyright (C) 2006 Christian Walter <wolti@sil.at>
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  *
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  * This library is free software; you can redistribute it and/or
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  * modify it under the terms of the GNU Lesser General Public
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  * License as published by the Free Software Foundation; either
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  * version 2.1 of the License, or (at your option) any later version.
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  *
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  * This library is distributed in the hope that it will be useful,
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  * but WITHOUT ANY WARRANTY; without even the implied warranty of
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  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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  * Lesser General Public License for more details.
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  *
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  * You should have received a copy of the GNU Lesser General Public
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  * License along with this library; if not, write to the Free Software
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  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
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  */
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/* ----------------------- System includes ----------------------------------*/
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#include "stdlib.h"
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#include "string.h"
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/* ----------------------- Platform includes --------------------------------*/
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#include "port.h"
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/* ----------------------- Modbus includes ----------------------------------*/
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#include "mb.h"
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#include "mbframe.h"
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#include "mbproto.h"
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#include "mbconfig.h"
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/* ----------------------- Defines ------------------------------------------*/
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#define MB_PDU_FUNC_READ_ADDR_OFF           ( MB_PDU_DATA_OFF )
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#define MB_PDU_FUNC_READ_DISCCNT_OFF        ( MB_PDU_DATA_OFF + 2 )
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#define MB_PDU_FUNC_READ_SIZE               ( 4 )
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#define MB_PDU_FUNC_READ_DISCCNT_MAX        ( 0x07D0 )
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/* ----------------------- Static functions ---------------------------------*/
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eMBException    prveMBError2Exception( eMBErrorCode eErrorCode );
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/* ----------------------- Start implementation -----------------------------*/
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#if MB_FUNC_READ_COILS_ENABLED > 0
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eMBException
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eMBFuncReadDiscreteInputs( UCHAR * pucFrame, USHORT * usLen )
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{
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    USHORT          usRegAddress;
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    USHORT          usDiscreteCnt;
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    UCHAR           ucNBytes;
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    UCHAR          *pucFrameCur;
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    eMBException    eStatus = MB_EX_NONE;
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    eMBErrorCode    eRegStatus;
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    if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )
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    {
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        usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );
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        usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );
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        usRegAddress++;
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        usDiscreteCnt = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF] << 8 );
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        usDiscreteCnt |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF + 1] );
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        /* Check if the number of registers to read is valid. If not
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         * return Modbus illegal data value exception. 
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         */
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        if( ( usDiscreteCnt >= 1 ) &&
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            ( usDiscreteCnt < MB_PDU_FUNC_READ_DISCCNT_MAX ) )
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        {
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            /* Set the current PDU data pointer to the beginning. */
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            pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
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            *usLen = MB_PDU_FUNC_OFF;
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            /* First byte contains the function code. */
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            *pucFrameCur++ = MB_FUNC_READ_DISCRETE_INPUTS;
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            *usLen += 1;
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            /* Test if the quantity of coils is a multiple of 8. If not last
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             * byte is only partially field with unused coils set to zero. */
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            if( ( usDiscreteCnt & 0x0007 ) != 0 )
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            {
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                ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 + 1 );
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            }
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            else
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            {
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                ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 );
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            }
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            *pucFrameCur++ = ucNBytes;
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            *usLen += 1;
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            eRegStatus =
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                eMBRegDiscreteCB( pucFrameCur, usRegAddress, usDiscreteCnt );
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            /* If an error occured convert it into a Modbus exception. */
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            if( eRegStatus != MB_ENOERR )
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            {
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                eStatus = prveMBError2Exception( eRegStatus );
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            }
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            else
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            {
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                /* The response contains the function code, the starting address
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                 * and the quantity of registers. We reuse the old values in the 
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                 * buffer because they are still valid. */
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                *usLen += ucNBytes;;
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            }
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        }
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        else
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        {
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            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
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        }
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    }
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    else
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    {
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        /* Can't be a valid read coil register request because the length
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         * is incorrect. */
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        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
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    }
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    return eStatus;
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}
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#endif