mbfuncdisc.cpp

00001  /*
00002   * FreeRTOS Modbus Libary: A Modbus serial implementation for FreeRTOS
00003   * Copyright (C) 2006 Christian Walter <wolti@sil.at>
00004   *
00005   * This library is free software; you can redistribute it and/or
00006   * modify it under the terms of the GNU Lesser General Public
00007   * License as published by the Free Software Foundation; either
00008   * version 2.1 of the License, or (at your option) any later version.
00009   *
00010   * This library is distributed in the hope that it will be useful,
00011   * but WITHOUT ANY WARRANTY; without even the implied warranty of
00012   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013   * Lesser General Public License for more details.
00014   *
00015   * You should have received a copy of the GNU Lesser General Public
00016   * License along with this library; if not, write to the Free Software
00017   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
00018   */
00019 
00020 
00021 
00022 /* ----------------------- System includes ----------------------------------*/
00023 #include "stdlib.h"
00024 #include "string.h"
00025 
00026 /* ----------------------- Platform includes --------------------------------*/
00027 #include "port.h"
00028 
00029 /* ----------------------- Modbus includes ----------------------------------*/
00030 #include "mb.h"
00031 #include "mbframe.h"
00032 #include "mbproto.h"
00033 #include "mbconfig.h"
00034 
00035 /* ----------------------- Defines ------------------------------------------*/
00036 #define MB_PDU_FUNC_READ_ADDR_OFF           ( MB_PDU_DATA_OFF )
00037 #define MB_PDU_FUNC_READ_DISCCNT_OFF        ( MB_PDU_DATA_OFF + 2 )
00038 #define MB_PDU_FUNC_READ_SIZE               ( 4 )
00039 #define MB_PDU_FUNC_READ_DISCCNT_MAX        ( 0x07D0 )
00040 
00041 /* ----------------------- Static functions ---------------------------------*/
00042 eMBException    prveMBError2Exception( eMBErrorCode eErrorCode );
00043 
00044 /* ----------------------- Start implementation -----------------------------*/
00045 
00046 #if MB_FUNC_READ_COILS_ENABLED > 0
00047 
00048 eMBException
00049 eMBFuncReadDiscreteInputs( UCHAR * pucFrame, USHORT * usLen )
00050 {
00051     USHORT          usRegAddress;
00052     USHORT          usDiscreteCnt;
00053     UCHAR           ucNBytes;
00054     UCHAR          *pucFrameCur;
00055 
00056     eMBException    eStatus = MB_EX_NONE;
00057     eMBErrorCode    eRegStatus;
00058 
00059     if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )
00060     {
00061         usRegAddress = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );
00062         usRegAddress |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );
00063         usRegAddress++;
00064 
00065         usDiscreteCnt = ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF] << 8 );
00066         usDiscreteCnt |= ( USHORT )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF + 1] );
00067 
00068         /* Check if the number of registers to read is valid. If not
00069          * return Modbus illegal data value exception. 
00070          */
00071         if( ( usDiscreteCnt >= 1 ) &&
00072             ( usDiscreteCnt < MB_PDU_FUNC_READ_DISCCNT_MAX ) )
00073         {
00074             /* Set the current PDU data pointer to the beginning. */
00075             pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
00076             *usLen = MB_PDU_FUNC_OFF;
00077 
00078             /* First byte contains the function code. */
00079             *pucFrameCur++ = MB_FUNC_READ_DISCRETE_INPUTS;
00080             *usLen += 1;
00081 
00082             /* Test if the quantity of coils is a multiple of 8. If not last
00083              * byte is only partially field with unused coils set to zero. */
00084             if( ( usDiscreteCnt & 0x0007 ) != 0 )
00085             {
00086                 ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 + 1 );
00087             }
00088             else
00089             {
00090                 ucNBytes = ( UCHAR ) ( usDiscreteCnt / 8 );
00091             }
00092             *pucFrameCur++ = ucNBytes;
00093             *usLen += 1;
00094 
00095             eRegStatus =
00096                 eMBRegDiscreteCB( pucFrameCur, usRegAddress, usDiscreteCnt );
00097 
00098             /* If an error occured convert it into a Modbus exception. */
00099             if( eRegStatus != MB_ENOERR  )
00100             {
00101                 eStatus = prveMBError2Exception( eRegStatus );
00102             }
00103             else
00104             {
00105                 /* The response contains the function code, the starting address
00106                  * and the quantity of registers. We reuse the old values in the 
00107                  * buffer because they are still valid. */
00108                 *usLen += ucNBytes;;
00109             }
00110         }
00111         else
00112         {
00113             eStatus = MB_EX_ILLEGAL_DATA_VALUE;
00114         }
00115     }
00116     else
00117     {
00118         /* Can't be a valid read coil register request because the length
00119          * is incorrect. */
00120         eStatus = MB_EX_ILLEGAL_DATA_VALUE;
00121     }
00122     return eStatus;
00123 }
00124 
00125 #endif