Tooltron

/* 

 * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.

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

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. The name of the author may not be used to endorse or promote products

 *    derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 *

 * File: $Id: mbrtu.c,v 1.18 2007/09/12 10:15:56 wolti Exp $

 */

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

#include "stdlib.h"

#include "string.h"

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

#include "port.h"

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

#include "mb.h"

#include "mbrtu.h"

#include "mbframe.h"

#include "mbcrc.h"

#include "mbport.h"

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

#define MB_SER_PDU_SIZE_MIN     4       /*!< Minimum size of a Modbus RTU frame. */

#define MB_SER_PDU_SIZE_MAX     256     /*!< Maximum size of a Modbus RTU frame. */

#define MB_SER_PDU_SIZE_CRC     2       /*!< Size of CRC 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_INIT,              /*!< Receiver is in initial state. */

    STATE_RX_IDLE,              /*!< Receiver is in idle state. */

    STATE_RX_RCV,               /*!< Frame is beeing received. */

    STATE_RX_ERROR              /*!< If the frame is invalid. */

} eMBRcvState;

typedef enum

{

    STATE_TX_IDLE,              /*!< Transmitter is in idle state. */

    STATE_TX_XMIT               /*!< Transmitter is in transfer state. */

} eMBSndState;

/* ----------------------- Static variables ---------------------------------*/

static volatile eMBSndState eSndState;

static volatile eMBRcvState eRcvState;

volatile UCHAR  ucRTUBuf[MB_SER_PDU_SIZE_MAX];

static volatile UCHAR *pucSndBufferCur;

static volatile USHORT usSndBufferCount;

static volatile USHORT usRcvBufferPos;

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

eMBErrorCode

eMBRTUInit( UCHAR ucSlaveAddress, UCHAR ucPort, ULONG ulBaudRate, eMBParity eParity )

{

    eMBErrorCode    eStatus = MB_ENOERR;

    ULONG           usTimerT35_50us;

    ( void )ucSlaveAddress;

    ENTER_CRITICAL_SECTION(  );

    /* Modbus RTU uses 8 Databits. */

    if( xMBPortSerialInit( ucPort, ulBaudRate, 8, eParity ) != TRUE )

    {

        eStatus = MB_EPORTERR;

    }

    else

    {

        /* If baudrate > 19200 then we should use the fixed timer values

         * t35 = 1750us. Otherwise t35 must be 3.5 times the character time.

         */

        if( ulBaudRate > 19200 )

        {

            usTimerT35_50us = 35;       /* 1800us. */

        }

        else

        {

            /* The timer reload value for a character is given by:

             *

             * ChTimeValue = Ticks_per_1s / ( Baudrate / 11 )

             *             = 11 * Ticks_per_1s / Baudrate

             *             = 220000 / Baudrate

             * The reload for t3.5 is 1.5 times this value and similary

             * for t3.5.

             */

            usTimerT35_50us = ( 7UL * 220000UL ) / ( 2UL * ulBaudRate );

        }

        if( xMBPortTimersInit( ( USHORT ) usTimerT35_50us ) != TRUE )

        {

            eStatus = MB_EPORTERR;

        }

    }

    EXIT_CRITICAL_SECTION(  );

    return eStatus;

}

void

eMBRTUStart( void )

{

    ENTER_CRITICAL_SECTION(  );

    /* Initially the receiver is in the state STATE_RX_INIT. we start

     * the timer and if no character is received within t3.5 we change

     * to STATE_RX_IDLE. This makes sure that we delay startup of the

     * modbus protocol stack until the bus is free.

     */

    eRcvState = STATE_RX_INIT;

    vMBPortSerialEnable( TRUE, FALSE );

    vMBPortTimersEnable(  );

    EXIT_CRITICAL_SECTION(  );

}

void

eMBRTUStop( void )

{

    ENTER_CRITICAL_SECTION(  );

    vMBPortSerialEnable( FALSE, FALSE );

    vMBPortTimersDisable(  );

    EXIT_CRITICAL_SECTION(  );

}

eMBErrorCode

eMBRTUReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength )

{

    BOOL            xFrameReceived = FALSE;

    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 )

        && ( usMBCRC16( ( UCHAR * ) ucRTUBuf, 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 = ucRTUBuf[MB_SER_PDU_ADDR_OFF];

        /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus

         * size of address field and CRC checksum.

         */

        *pusLength = ( USHORT )( usRcvBufferPos - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_CRC );

        /* Return the start of the Modbus PDU to the caller. */

        *pucFrame = ( UCHAR * ) & ucRTUBuf[MB_SER_PDU_PDU_OFF];

        xFrameReceived = TRUE;

    }

    else

    {

        eStatus = MB_EIO;

    }

    EXIT_CRITICAL_SECTION(  );

    return eStatus;

}

eMBErrorCode

eMBRTUSend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength )

{

    eMBErrorCode    eStatus = MB_ENOERR;

    USHORT          usCRC16;

    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 CRC16 checksum for Modbus-Serial-Line-PDU. */

        usCRC16 = usMBCRC16( ( UCHAR * ) pucSndBufferCur, usSndBufferCount );

        ucRTUBuf[usSndBufferCount++] = ( UCHAR )( usCRC16 & 0xFF );

        ucRTUBuf[usSndBufferCount++] = ( UCHAR )( usCRC16 >> 8 );

        /* Activate the transmitter. */

        eSndState = STATE_TX_XMIT;

        vMBPortSerialEnable( FALSE, TRUE );

    }

    else

    {

        eStatus = MB_EIO;

    }

    EXIT_CRITICAL_SECTION(  );

    return eStatus;

}

BOOL

xMBRTUReceiveFSM( void )

{

    BOOL            xTaskNeedSwitch = FALSE;

    UCHAR           ucByte;

    assert( eSndState == STATE_TX_IDLE );

    /* Always read the character. */

    ( void )xMBPortSerialGetByte( ( CHAR * ) & ucByte );

    switch ( eRcvState )

    {

        /* If we have received a character in the init state we have to

         * wait until the frame is finished.

         */

    case STATE_RX_INIT:

        vMBPortTimersEnable(  );

        break;

        /* In the error state we wait until all characters in the

         * damaged frame are transmitted.

         */

    case STATE_RX_ERROR:

        vMBPortTimersEnable(  );

        break;

        /* In the idle state we wait for a new character. If a character

         * is received the t1.5 and t3.5 timers are started and the

         * receiver is in the state STATE_RX_RECEIVCE.

         */

    case STATE_RX_IDLE:

        usRcvBufferPos = 0;

        ucRTUBuf[usRcvBufferPos++] = ucByte;

        eRcvState = STATE_RX_RCV;

        /* Enable t3.5 timers. */

        vMBPortTimersEnable(  );

        break;

        /* We are currently receiving a frame. Reset the timer after

         * every character received. If more than the maximum possible

         * number of bytes in a modbus frame is received the frame is

         * ignored.

         */

    case STATE_RX_RCV:

        if( usRcvBufferPos < MB_SER_PDU_SIZE_MAX )

        {

            ucRTUBuf[usRcvBufferPos++] = ucByte;

        }

        else

        {

            eRcvState = STATE_RX_ERROR;

        }

        vMBPortTimersEnable(  );

        break;

    }

    return xTaskNeedSwitch;

}

BOOL

xMBRTUTransmitFSM( void )

{

    BOOL            xNeedPoll = FALSE;

    assert( eRcvState == STATE_RX_IDLE );

    switch ( eSndState )

    {

        /* 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;

    case STATE_TX_XMIT:

        /* check if we are finished. */

        if( usSndBufferCount != 0 )

        {

            xMBPortSerialPutByte( ( CHAR )*pucSndBufferCur );

            pucSndBufferCur++;  /* next byte in sendbuffer. */

            usSndBufferCount--;

        }

        else

        {

            xNeedPoll = xMBPortEventPost( EV_FRAME_SENT );

            /* Disable transmitter. This prevents another transmit buffer

             * empty interrupt. */

            vMBPortSerialEnable( TRUE, FALSE );

            eSndState = STATE_TX_IDLE;

        }

        break;

    }

    return xNeedPoll;

}

BOOL

xMBRTUTimerT35Expired( void )

{

    BOOL            xNeedPoll = FALSE;

    switch ( eRcvState )

    {

        /* Timer t35 expired. Startup phase is finished. */

    case STATE_RX_INIT:

        xNeedPoll = xMBPortEventPost( EV_READY );

        break;

        /* A frame was received and t35 expired. Notify the listener that

         * a new frame was received. */

    case STATE_RX_RCV:

        xNeedPoll = xMBPortEventPost( EV_FRAME_RECEIVED );

        break;

        /* An error occured while receiving the frame. */

    case STATE_RX_ERROR:

        break;

        /* Function called in an illegal state. */

    default:

        assert( ( eRcvState == STATE_RX_INIT ) ||

                ( eRcvState == STATE_RX_RCV ) || ( eRcvState == STATE_RX_ERROR ) );

    }

    vMBPortTimersDisable(  );

    eRcvState = STATE_RX_IDLE;

    return xNeedPoll;

}