mbascii.c

freemodbus-v019.zip 是v0.19版本的代码

 /*
  * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
  * Copyright (C) 2006 Christian Walter <[e-mail]>
  *
  * 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
  *
  * File: $Id: mbascii.c,v 1.11 2006/06/18 09:57:03 wolti Exp $
  */

/* ----------------------- System includes ----------------------------------*/
#include "stdlib.h"
#include "string.h"

/* ----------------------- Platform includes --------------------------------*/
#include "port.h"

/* ----------------------- Modbus includes ----------------------------------*/
#include "mb.h"
#include "mbconfig.h"
#include "mbascii.h"
#include "mbframe.h"

#include "mbcrc.h"
#include "mbport.h"

#if MB_ASCII_ENABLED > 0

/* ----------------------- Defines ------------------------------------------*/
#define MB_ASCII_DEFAULT_CR     '\r'    /*!< Default CR character for Modbus ASCII. */
#define MB_ASCII_DEFAULT_LF     '\n'    /*!< Default LF character for Modbus ASCII. */
#define MB_SER_PDU_SIZE_MIN     3       /*!< Minimum size of a Modbus ASCII frame. */
#define MB_SER_PDU_SIZE_MAX     256     /*!< Maximum size of a Modbus ASCII frame. */
#define MB_SER_PDU_SIZE_LRC     1       /*!< Size of LRC field in PDU. */
#define MB_SER_PDU_ADDR_OFF     0       /*!< Offset of slave address in Ser-PDU. */
#define MB_SER_PDU_PDU_OFF      1       /*!< Offset of Modbus-PDU in Ser-PDU. */

/* ----------------------- Type definitions ---------------------------------*/
typedef enum
{
    STATE_RX_IDLE,              /*!< Receiver is in idle state. */
    STATE_RX_RCV,               /*!< Frame is beeing received. */
    STATE_RX_WAIT_EOF           /*!< Wait for End of Frame. */
} eMBRcvState;

typedef enum
{
    STATE_TX_IDLE,              /*!< Transmitter is in idle state. */
    STATE_TX_START,             /*!< Starting transmission (':' sent). */
    STATE_TX_DATA,              /*!< Sending of data (Address, Data, LRC). */
    STATE_TX_END,               /*!< End of transmission. */
    STATE_TX_NOTIFY,            /*!< Notify sender that the frame has been sent. */
} eMBSndState;

typedef enum
{
    BYTE_HIGH_NIBBLE,           /*!< Character for high nibble of byte. */
    BYTE_LOW_NIBBLE             /*!< Character for low nibble of byte. */
} eMBBytePos;

/* ----------------------- Static functions ---------------------------------*/
static UCHAR    prvucMBCHAR2BIN( UCHAR ucCharacter );

static UCHAR    prvucMBBIN2CHAR( UCHAR ucByte );

static UCHAR    prvucMBLRC( UCHAR * pucFrame, USHORT usLen );

/* ----------------------- Static variables ---------------------------------*/
static volatile eMBSndState eSndState;
static volatile eMBRcvState eRcvState;

/* We reuse the Modbus RTU buffer because only one buffer is needed and the
 * RTU buffer is bigger. */
extern volatile UCHAR ucRTUBuf[];
static volatile UCHAR *ucASCIIBuf = ucRTUBuf;

static volatile USHORT usRcvBufferPos;
static volatile eMBBytePos eBytePos;

static volatile UCHAR *pucSndBufferCur;
static volatile USHORT usSndBufferCount;

static volatile UCHAR ucLRC;
static volatile UCHAR ucMBLFCharacter;

/* ----------------------- Start implementation -----------------------------*/
eMBErrorCode
eMBASCIIInit( UCHAR ucSlaveAddress, UCHAR ucPort, ULONG ulBaudRate,
              eMBParity eParity )
{
    eMBErrorCode    eStatus = MB_ENOERR;

    ENTER_CRITICAL_SECTION(  );
    ucMBLFCharacter = MB_ASCII_DEFAULT_LF;

    if( xMBPortSerialInit( ucPort, ulBaudRate, 7, eParity ) != TRUE )
    {
        eStatus = MB_EPORTERR;
    }

    if( xMBPortTimersInit( MB_ASCII_TIMEOUT_SEC * 20000UL ) != TRUE )
    {
        eStatus = MB_EPORTERR;
    }

    EXIT_CRITICAL_SECTION(  );

    return eStatus;
}

void
eMBASCIIStart( void )
{
    ENTER_CRITICAL_SECTION(  );
    vMBPortSerialEnable( TRUE, FALSE );
    eRcvState = STATE_RX_IDLE;
    EXIT_CRITICAL_SECTION(  );

    /* No special startup required for ASCII. */
    ( void )xMBPortEventPost( EV_READY );
}

void
eMBASCIIStop( void )
{
    ENTER_CRITICAL_SECTION(  );
    vMBPortSerialEnable( FALSE, FALSE );
    vMBPortTimersDisable(  );
    EXIT_CRITICAL_SECTION(  );
}

eMBErrorCode
eMBASCIIReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength )
{
    eMBErrorCode    eStatus = MB_ENOERR;

    ENTER_CRITICAL_SECTION(  );
    assert( usRcvBufferPos < MB_SER_PDU_SIZE_MAX );

    /* Length and CRC check */
    if( ( usRcvBufferPos >= MB_SER_PDU_SIZE_MIN )
        && ( prvucMBLRC( ( UCHAR * ) ucASCIIBuf, usRcvBufferPos ) == 0 ) )
    {
        /* Save the address field. All frames are passed to the upper layed
         * and the decision if a frame is used is done there.
         */
        *pucRcvAddress = ucASCIIBuf[MB_SER_PDU_ADDR_OFF];

        /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus
         * size of address field and CRC checksum.
         */
        *pusLength = usRcvBufferPos - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_LRC;

        /* Return the start of the Modbus PDU to the caller. */
        *pucFrame = ( UCHAR * ) & ucASCIIBuf[MB_SER_PDU_PDU_OFF];
    }
    else
    {
        eStatus = MB_EIO;
    }
    EXIT_CRITICAL_SECTION(  );
    return eStatus;
}

eMBErrorCode
eMBASCIISend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength )
{
    eMBErrorCode    eStatus = MB_ENOERR;
    UCHAR           usLRC;

    ENTER_CRITICAL_SECTION(  );
    /* Check if the receiver is still in idle state. If not we where to
     * slow with processing the received frame and the master sent another
     * frame on the network. We have to abort sending the frame.
     */
    if( eRcvState == STATE_RX_IDLE )
    {
        /* First byte before the Modbus-PDU is the slave address. */
        pucSndBufferCur = ( UCHAR * ) pucFrame - 1;
        usSndBufferCount = 1;

        /* Now copy the Modbus-PDU into the Modbus-Serial-Line-PDU. */
        pucSndBufferCur[MB_SER_PDU_ADDR_OFF] = ucSlaveAddress;
        usSndBufferCount += usLength;

        /* Calculate LRC checksum for Modbus-Serial-Line-PDU. */
        usLRC = prvucMBLRC( ( UCHAR * ) pucSndBufferCur, usSndBufferCount );
        ucASCIIBuf[usSndBufferCount++] = usLRC;

        /* Activate the transmitter. */
        eSndState = STATE_TX_START;
        vMBPortSerialEnable( FALSE, TRUE );
    }
    else
    {
        eStatus = MB_EIO;
    }
    EXIT_CRITICAL_SECTION(  );
    return eStatus;
}

BOOL
xMBASCIIReceiveFSM( void )
{
    BOOL            xNeedPoll = FALSE;
    UCHAR           ucByte;
    UCHAR           ucResult;

    assert( eSndState == STATE_TX_IDLE );

    ( void )xMBPortSerialGetByte( &ucByte );
    switch ( eRcvState )
    {
            /* A new character is received. If the character is a ':' the input
             * buffer is cleared. A CR-character signals the end of the data
             * block. Other characters are part of the data block and their
             * ASCII value is converted back to a binary representation.
             */
        case STATE_RX_RCV:
            /* Enable timer for character timeout. */
            vMBPortTimersEnable(  );
            if( ucByte == ':' )
            {
                /* Empty receive buffer. */
                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] = 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( 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( *pucSndBufferCur >> 4 );
                        xMBPortSerialPutByte( ucByte );
                        eBytePos = BYTE_LOW_NIBBLE;
                        break;

                    case BYTE_LOW_NIBBLE:
                        ucByte = prvucMBBIN2CHAR( *pucSndBufferCur & 0x0F );
                        xMBPortSerialPutByte( 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( 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;
}


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

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


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