Modbus Implimentation code

**AJITnayak** · 04-09-2014

Dear all.

I have attached my code below . I have few question here.
Arduino - WordCast
question are:
1) I have value latitude 13.08. Here 13 should put in lower byte of word and 08 into higher order of byte address. How to assign it
2)i have analog sensor which read analog voltage 0-5v . that being converted from +75 deg to -75 degree.
from 0-75 degree i can read value properly on QMODBUS, But 0 to -75 master varying with 65561 value.How to covert it to -ve value.
3) IS it possible to assign our own slave address in below code

Code:

#define  MAX_BUFFER  64    
typedef struct {
  uint8_t u8id;          /*!< slave address between 1 and 247. 0 means broadcast */
  uint8_t u8fct;         /*!< function code: 1, 2, 3, 4, 5, 6, 15 or 16 */
  uint16_t u16RegAdd;    /*!< address of the first register to access at slave/s */
  uint16_t u16CoilsNo;   /*!< number of coils or registers to access */
  uint16_t *au16reg;     /*!< pointer to memory image in master */
}
modbus_t;

enum {
  RESPONSE_SIZE = 6,
  EXCEPTION_SIZE = 3,
  CHECKSUM_SIZE = 2
};

enum MESSAGE {
  ID                             = 0,
  FUNC,
  ADD_HI,
  ADD_LO,
  NB_HI,
  NB_LO,
  BYTE_CNT
};

enum MB_FC {
  MB_FC_NONE                     = 0,   /*!< null operator */
  MB_FC_READ_COILS               = 1,    /*!< FCT=1 -> read coils or digital outputs */
  MB_FC_READ_DISCRETE_INPUT      = 2,    /*!< FCT=2 -> read digital inputs */
  MB_FC_READ_REGISTERS           = 3,    /*!< FCT=3 -> read registers or analog outputs */
  MB_FC_READ_INPUT_REGISTER      = 4,    /*!< FCT=4 -> read analog inputs */
  MB_FC_WRITE_COIL               = 5,    /*!< FCT=5 -> write single coil or output */
  MB_FC_WRITE_REGISTER           = 6,    /*!< FCT=6 -> write single register */
  MB_FC_WRITE_MULTIPLE_COILS     = 15,    /*!< FCT=15 -> write multiple coils or outputs */
  MB_FC_WRITE_MULTIPLE_REGISTERS = 16    /*!< FCT=16 -> write multiple registers */
};

enum COM_STATES {
  COM_IDLE                     = 0,
  COM_WAITING                  = 1

};

enum ERR_LIST {
  ERR_NOT_MASTER                = -1,
  ERR_POLLING                   = -2,
  ERR_BUFF_OVERFLOW             = -3,
  ERR_BAD_CRC                   = -4,
  ERR_EXCEPTION                 = -5
};


enum {
  NO_REPLY = 255,             /*!< */
  EXC_FUNC_CODE = 1,        /*!< Function code not available */
  EXC_ADDR_RANGE = 2,         /*!< Address beyond available space for Modbus registers */
  EXC_REGS_QUANT = 3,          /*!< Coils or registers number beyond the available space */
  EXC_EXECUTE = 4             /*!< */
};


const unsigned char fctsupported[] = {
  MB_FC_READ_COILS,
  MB_FC_READ_DISCRETE_INPUT,
  MB_FC_READ_REGISTERS,
  MB_FC_READ_INPUT_REGISTER,
  MB_FC_WRITE_COIL,
  MB_FC_WRITE_REGISTER,
  MB_FC_WRITE_MULTIPLE_COILS,
  MB_FC_WRITE_MULTIPLE_REGISTERS
};

#define T35  5

class Modbus {
private:
  HardwareSerial *port; //!< Pointer to Serial class object
  uint8_t u8id; //!<0=master, 1..247=slave number
  uint8_t u8serno; //!<serial port: 0-Serial, 1..3-Serial1..Serial3
  uint8_t u8txenpin; //!<flow control pin: 0=USB or RS-232 mode, >0=RS-485 mode
  uint8_t u8state;
  uint8_t au8Buffer[MAX_BUFFER];
  uint8_t u8BufferSize;
  uint8_t u8lastRec;
  uint16_t *au16regs;
  uint16_t u16InCnt, u16OutCnt, u16errCnt;
  uint16_t u16timeOut;
  uint32_t u32time, u32timeOut;
  uint8_t u8regsize;

  void init(uint8_t u8id, uint8_t u8serno, uint8_t u8txenpin);
  void sendTxBuffer(); // transmit buffer to serial port
  int8_t getRxBuffer(); // get serial buffer contents
  uint16_t calcCRC(uint8_t u8length); // get CRC from au8Buffer until u8length
  uint8_t validateAnswer();
  uint8_t validateRequest(); // validate master request
  void get_FC1(); // *** only master ***
  void get_FC3(); // *** only master ***
  int8_t process_FC1( uint16_t *regs, uint8_t u8size ); //!< *** only slave ***
  int8_t process_FC3( uint16_t *regs, uint8_t u8size ); //!< *** only slave ***
  int8_t process_FC5( uint16_t *regs, uint8_t u8size ); //!< *** only slave ***
  int8_t process_FC6( uint16_t *regs, uint8_t u8size ); //!< *** only slave ***
  int8_t process_FC15( uint16_t *regs, uint8_t u8size ); //!< *** only slave ***
  int8_t process_FC16( uint16_t *regs, uint8_t u8size ); //!< *** only slave ***
  void buildException( uint8_t u8exception ); // build exception message

public:
  Modbus(); // !< Default Constructor
  Modbus(uint8_t u8id, uint8_t u8serno); // !< Constructor
  Modbus(uint8_t u8id, uint8_t u8serno, uint8_t u8txenpin); // !< Full Constructor
  void begin(long u32speed);
  void begin();
  void setTimeOut( uint16_t u16timeout); //!< write communication watch-dog timer
  uint16_t getTimeOut(); //!< get communication watch-dog timer value
  boolean getTimeOutState(); //!< get communication watch-dog timer state
  int8_t query( modbus_t telegram ); //!< only for master
  int8_t poll(); //!< cyclic poll for master
  int8_t poll( uint16_t *regs, uint8_t u8size ); //!< cyclic poll for slave
  uint16_t getInCnt(); //!< number of incoming messages
  uint16_t getOutCnt(); //!< number of outcoming messages
  uint16_t getErrCnt(); //!< error counter
  uint8_t getID(); //!< get slave ID between 1 and 247
  uint8_t getState();
  uint8_t getLastError(); //!< get last error message
  void setID( uint8_t u8id ); //!< write new ID for the slave
  void end(); //!< finish any communication and release serial communication port
};


Modbus::Modbus() {
  init(0, 0, 0);
}


Modbus::Modbus(uint8_t u8id, uint8_t u8serno) {
  init(u8id, u8serno, 0);
}

Modbus::Modbus(uint8_t u8id, uint8_t u8serno, uint8_t u8txenpin) {
  init(u8id, u8serno, u8txenpin);
}


void Modbus::begin(long u32speed) {

  switch ( u8serno ) {
#if defined(UBRR1H)
  case 1:
    port = &Serial1;
    break;
#endif

#if defined(UBRR2H)
  case 2:
    port = &Serial2;
    break;
#endif

#if defined(UBRR3H)
  case 3:
    port = &Serial3;
    break;
#endif
  case 0:
  default:
    port = &Serial;
    break;
  }

  // port->begin(u32speed, u8config);
  port->begin(u32speed);
  if (u8txenpin > 1) { // pin 0 & pin 1 are reserved for RX/TX
    // return RS485 transceiver to transmit mode
    pinMode(u8txenpin, OUTPUT);
    digitalWrite(u8txenpin, LOW);
  }

  port->flush();
  u8lastRec = u8BufferSize = 0;
  u16InCnt = u16OutCnt = u16errCnt = 0;
}


void Modbus::begin() {
  begin(19200);
}

void Modbus::setID( uint8_t u8id) {
  if (( u8id != 0) && (u8id <= 247)) {
    this->u8id = u8id;
  }
}


uint8_t Modbus::getID() {
  return this->u8id;
}


void Modbus::setTimeOut( uint16_t u16timeOut) {
  this->u16timeOut = u16timeOut;
}


boolean Modbus::getTimeOutState() {
  return (millis() > u32timeOut);
}


uint16_t Modbus::getInCnt() {
  return u16InCnt;
}


uint16_t Modbus::getOutCnt() {
  return u16OutCnt;
}

uint16_t Modbus::getErrCnt() {
  return u16errCnt;
}


uint8_t Modbus::getState() {
  return u8state;
}


int8_t Modbus::query( modbus_t telegram ) {
  uint8_t u8regsno, u8bytesno;
  if (u8id != 0) return -2;
  if (u8state != COM_IDLE) return -1;

  if ((telegram.u8id == 0) || (telegram.u8id > 247)) return -3;

  au16regs = telegram.au16reg;

  // telegram header
  au8Buffer[ ID ]         = telegram.u8id;
  au8Buffer[ FUNC ]       = telegram.u8fct;
  au8Buffer[ ADD_HI ]     = highByte(telegram.u16RegAdd );
  au8Buffer[ ADD_LO ]     = lowByte( telegram.u16RegAdd );

  switch ( telegram.u8fct ) {
  case MB_FC_READ_COILS:
  case MB_FC_READ_DISCRETE_INPUT:
  case MB_FC_READ_REGISTERS:
  case MB_FC_READ_INPUT_REGISTER:
    au8Buffer[ NB_HI ]      = highByte(telegram.u16CoilsNo );
    au8Buffer[ NB_LO ]      = lowByte( telegram.u16CoilsNo );
    u8BufferSize = 6;
    break;
  case MB_FC_WRITE_COIL:
    au8Buffer[ NB_HI ]      = ((au16regs[0] > 0) ? 0xff : 0);
    au8Buffer[ NB_LO ]      = 0;
    u8BufferSize = 6;
    break;
  case MB_FC_WRITE_REGISTER:
    au8Buffer[ NB_HI ]      = highByte(au16regs[0]);
    au8Buffer[ NB_LO ]      = lowByte(au16regs[0]);
    u8BufferSize = 6;
    break;
  case MB_FC_WRITE_MULTIPLE_COILS:
    u8regsno = telegram.u16CoilsNo / 16;
    u8bytesno = u8regsno * 2;
    if ((telegram.u16CoilsNo % 16) != 0) {
      u8bytesno++;
      u8regsno++;
    }

    au8Buffer[ NB_HI ]      = highByte(telegram.u16CoilsNo );
    au8Buffer[ NB_LO ]      = lowByte( telegram.u16CoilsNo );
    au8Buffer[ NB_LO + 1 ]    = u8bytesno;
    u8BufferSize = 7;

    u8regsno = u8bytesno = 0; // now auxiliary registers
    for (uint16_t i = 0; i < telegram.u16CoilsNo; i++) {


    }
    break;

  case MB_FC_WRITE_MULTIPLE_REGISTERS:
    au8Buffer[ NB_HI ]      = highByte(telegram.u16CoilsNo );
    au8Buffer[ NB_LO ]      = lowByte( telegram.u16CoilsNo );
    au8Buffer[ NB_LO + 1 ]    = (uint8_t) ( telegram.u16CoilsNo * 2 );
    u8BufferSize = 7;

    for (uint16_t i = 0; i < telegram.u16CoilsNo; i++) {
      au8Buffer[ u8BufferSize ] = highByte( au16regs[ i ] );
      u8BufferSize++;
      au8Buffer[ u8BufferSize ] = lowByte( au16regs[ i ] );
      u8BufferSize++;
    }
    break;
  }

  sendTxBuffer();
  u8state = COM_WAITING;
  return 0;
}

int8_t Modbus::poll() {
  // check if there is any incoming frame
  uint8_t u8current = port->available();

  if (millis() > u32timeOut) {
    u8state = COM_IDLE;
    u16errCnt++;
    return 0;
  }

  if (u8current == 0) return 0;

  // check T35 after frame end or still no frame end
  if (u8current != u8lastRec) {
    u8lastRec = u8current;
    u32time = millis() + T35;
    return 0;
  }
  if (millis() < u32time) return 0;

  // transfer Serial buffer frame to auBuffer
  u8lastRec = 0;
  int8_t i8state = getRxBuffer();
  if (i8state < 7) {
    u8state = COM_IDLE;
    u16errCnt++;
    return i8state;
  }

  // validate message: id, CRC, FCT, exception
  uint8_t u8exception = validateAnswer();
  if (u8exception != 0) {
    u8state = COM_IDLE;
    return u8exception;
  }

  // process answer
  switch ( au8Buffer[ FUNC ] ) {
  case MB_FC_READ_COILS:
  case MB_FC_READ_DISCRETE_INPUT:
    // call get_FC1 to transfer the incoming message to au16regs buffer
    get_FC1( );
    break;
  case MB_FC_READ_INPUT_REGISTER:
  case MB_FC_READ_REGISTERS :
    // call get_FC3 to transfer the incoming message to au16regs buffer
    get_FC3( );
    break;
  case MB_FC_WRITE_COIL:
  case MB_FC_WRITE_REGISTER :
  case MB_FC_WRITE_MULTIPLE_COILS:
  case MB_FC_WRITE_MULTIPLE_REGISTERS :
    // nothing to do
    break;
  default:
    break;
  }
  u8state = COM_IDLE;
  return u8BufferSize;
}


int8_t Modbus::poll( uint16_t *regs, uint8_t u8size ) {

  au16regs = regs;
  u8regsize = u8size;

  // check if there is any incoming frame
  uint8_t u8current = port->available();
  if (u8current == 0) return 0;

  // check T35 after frame end or still no frame end
  if (u8current != u8lastRec) {
    u8lastRec = u8current;
    u32time = millis() + T35;
    return 0;
  }
  if (millis() < u32time) return 0;

  u8lastRec = 0;
  int8_t i8state = getRxBuffer();
  if (i8state < 7) return i8state;

  // check slave id
  if (au8Buffer[ ID ] != u8id) return 0;

  // validate message: CRC, FCT, address and size
  uint8_t u8exception = validateRequest();
  if (u8exception > 0) {
    if (u8exception != NO_REPLY) {
      buildException( u8exception );
      sendTxBuffer();
    }
    return u8exception;
  }

  u32timeOut = millis() + long(u16timeOut);

  // process message
  switch ( au8Buffer[ FUNC ] ) {
  case MB_FC_READ_COILS:
  case MB_FC_READ_DISCRETE_INPUT:
    return process_FC1( regs, u8size );
    break;
  case MB_FC_READ_INPUT_REGISTER:
  case MB_FC_READ_REGISTERS :
    return process_FC3( regs, u8size );
    break;
  case MB_FC_WRITE_COIL:
    return process_FC5( regs, u8size );
    break;
  case MB_FC_WRITE_REGISTER :
    return process_FC6( regs, u8size );
    break;
  case MB_FC_WRITE_MULTIPLE_COILS:
    return process_FC15( regs, u8size );
    break;
  case MB_FC_WRITE_MULTIPLE_REGISTERS :
    return process_FC16( regs, u8size );
    break;
  default:
    break;
  }
}

/* _____PRIVATE FUNCTIONS_____________________________________________________ */

void Modbus::init(uint8_t u8id, uint8_t u8serno, uint8_t u8txenpin) {
  this->u8id = u8id;
  this->u8serno = (u8serno > 3) ? 0 : u8serno;
  this->u8txenpin = u8txenpin;
  this->u16timeOut = 1000;
}


int8_t Modbus::getRxBuffer() {
  boolean bBuffOverflow = false;

  if (u8txenpin > 1) digitalWrite( u8txenpin, LOW );

  u8BufferSize = 0;
  while ( port->available() ) {
    au8Buffer[ u8BufferSize ] = port->read();
    u8BufferSize ++;

    if (u8BufferSize >= MAX_BUFFER) bBuffOverflow = true;
  }
  u16InCnt++;

  if (bBuffOverflow) {
    u16errCnt++;
    return ERR_BUFF_OVERFLOW;
  }
  return u8BufferSize;
}


void Modbus::sendTxBuffer() {
  uint8_t i = 0;

  // append CRC to message
  uint16_t u16crc = calcCRC( u8BufferSize );
  au8Buffer[ u8BufferSize ] = u16crc >> 8;
  u8BufferSize++;
  au8Buffer[ u8BufferSize ] = u16crc & 0x00ff;
  u8BufferSize++;

  // set RS485 transceiver to transmit mode
  if (u8txenpin > 1) {
    switch ( u8serno ) {
#if defined(UBRR1H)
    case 1:
      UCSR1A = UCSR1A | (1 << TXC1);
      break;
#endif

#if defined(UBRR2H)
    case 2:
      UCSR2A = UCSR2A | (1 << TXC2);
      break;
#endif

#if defined(UBRR3H)
    case 3:
      UCSR3A = UCSR3A | (1 << TXC3);
      break;
#endif
    case 0:
    default:
      UCSR0A = UCSR0A | (1 << TXC0);
      break;
    }
    digitalWrite( u8txenpin, HIGH );
  }

  // transfer buffer to serial line
  port->write( au8Buffer, u8BufferSize );

  // keep RS485 transceiver in transmit mode as long as sending
  if (u8txenpin > 1) {
    switch ( u8serno ) {
#if defined(UBRR1H)
    case 1:
      while (!(UCSR1A & (1 << TXC1)));
      break;
#endif

#if defined(UBRR2H)
    case 2:
      while (!(UCSR2A & (1 << TXC2)));
      break;
#endif

#if defined(UBRR3H)
    case 3:
      while (!(UCSR3A & (1 << TXC3)));
      break;
#endif
    case 0:
    default:
      while (!(UCSR0A & (1 << TXC0)));
      break;
    }

    // return RS485 transceiver to receive mode
    digitalWrite( u8txenpin, LOW );
  }
  port->flush();
  u8BufferSize = 0;

  // set time-out for master
  u32timeOut = millis() + (unsigned long) u16timeOut;

  // increase message counter
  u16OutCnt++;
}

/**
 * @brief
 * This method calculates CRC
 *
 * @return uint16_t calculated CRC value for the message
 * @ingroup buffer
 */
uint16_t Modbus::calcCRC(uint8_t u8length) {
  unsigned int temp, temp2, flag;
  temp = 0xFFFF;
  for (unsigned char i = 0; i < u8length; i++) {
    temp = temp ^ au8Buffer[i];
    for (unsigned char j = 1; j <= 8; j++) {
      flag = temp & 0x0001;
      temp >>= 1;
      if (flag)
        temp ^= 0xA001;
    }
  }
  // Reverse byte order.
  temp2 = temp >> 8;
  temp = (temp << 8) | temp2;
  temp &= 0xFFFF;
  // the returned value is already swapped
  // crcLo byte is first & crcHi byte is last
  return temp;
}

uint8_t Modbus::validateRequest() {
  // check message crc vs calculated crc
  uint16_t u16MsgCRC =
    ((au8Buffer[u8BufferSize - 2] << 8)
    | au8Buffer[u8BufferSize - 1]); // combine the crc Low & High bytes
  if ( calcCRC( u8BufferSize - 2 ) != u16MsgCRC ) {
    u16errCnt ++;
    return NO_REPLY;
  }

  // check fct code
  boolean isSupported = false;
  for (uint8_t i = 0; i < sizeof( fctsupported ); i++) {
    if (fctsupported[i] == au8Buffer[FUNC]) {
      isSupported = 1;
      break;
    }
  }
  if (!isSupported) {
    u16errCnt ++;
    return EXC_FUNC_CODE;
  }

  // check start address & nb range
  uint16_t u16regs = 0;
  uint8_t u8regs;
  switch ( au8Buffer[ FUNC ] ) {
  case MB_FC_READ_COILS:
  case MB_FC_READ_DISCRETE_INPUT:
  case MB_FC_WRITE_MULTIPLE_COILS:
    u16regs = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ]) / 16;
    u16regs += word( au8Buffer[ NB_HI ], au8Buffer[ NB_LO ]) / 16;
    u8regs = (uint8_t) u16regs;
    if (u8regs > u8regsize) return EXC_ADDR_RANGE;
    break;
  case MB_FC_WRITE_COIL:
    u16regs = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ]) / 16;
    u8regs = (uint8_t) u16regs;
    if (u8regs > u8regsize) return EXC_ADDR_RANGE;
    break;
  case MB_FC_WRITE_REGISTER :
    u16regs = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ]);
    u8regs = (uint8_t) u16regs;
    if (u8regs > u8regsize) return EXC_ADDR_RANGE;
    break;
  case MB_FC_READ_REGISTERS :
  case MB_FC_READ_INPUT_REGISTER :
  case MB_FC_WRITE_MULTIPLE_REGISTERS :
    u16regs = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ]);
    u16regs += word( au8Buffer[ NB_HI ], au8Buffer[ NB_LO ]);
    u8regs = (uint8_t) u16regs;
    if (u8regs > u8regsize) return EXC_ADDR_RANGE;
    break;
  }
  return 0; // OK, no exception code thrown
}


uint8_t Modbus::validateAnswer() {
  // check message crc vs calculated crc
  uint16_t u16MsgCRC =
    ((au8Buffer[u8BufferSize - 2] << 8)
    | au8Buffer[u8BufferSize - 1]); // combine the crc Low & High bytes
  if ( calcCRC( u8BufferSize - 2 ) != u16MsgCRC ) {
    u16errCnt ++;
    return NO_REPLY;
  }

  // check exception
  if ((au8Buffer[ FUNC ] & 0x80) != 0) {
    u16errCnt ++;
    return ERR_EXCEPTION;
  }

  // check fct code
  boolean isSupported = false;
  for (uint8_t i = 0; i < sizeof( fctsupported ); i++) {
    if (fctsupported[i] == au8Buffer[FUNC]) {
      isSupported = 1;
      break;
    }
  }
  if (!isSupported) {
    u16errCnt ++;
    return EXC_FUNC_CODE;
  }

  return 0; // OK, no exception code thrown
}


void Modbus::buildException( uint8_t u8exception ) {
  uint8_t u8func = au8Buffer[ FUNC ];  // get the original FUNC code

  au8Buffer[ ID ]      = u8id;
  au8Buffer[ FUNC ]    = u8func + 0x80;
  au8Buffer[ 2 ]       = u8exception;
  u8BufferSize         = EXCEPTION_SIZE;
}


void Modbus::get_FC1() {
  uint8_t u8byte, i;
  u8byte = 0;

  // check the answer length
  boolean bEvenOdd =
    ( au8Buffer[ ADD_HI ] % 2 == 0) ?
  false :
  true;

  uint8_t u8WordsNo =
    ( !bEvenOdd ) ?
  au8Buffer[ ADD_HI ] / 2 :
  au8Buffer[ ADD_HI ] / 2 + 1;

  for (i = 0; i < u8WordsNo; i++) {
    au16regs[ i ] = word(
    au8Buffer[ u8byte ],
    au8Buffer[ u8byte + 1 ]);
    u8byte += 2;
  }

  // cut last byte
  if (bEvenOdd) {
    au16regs[ u8WordsNo - 1 ] &= 0xff00;
  }
}

void Modbus::get_FC3() {
  uint8_t u8byte, i;
  u8byte = 3;

  for (i = 0; i < au8Buffer[ 2 ] / 2; i++) {
    au16regs[ i ] = word(
    au8Buffer[ u8byte ],
    au8Buffer[ u8byte + 1 ]);
    u8byte += 2;
  }
}


int8_t Modbus::process_FC1( uint16_t *regs, uint8_t u8size ) {
  uint8_t u8currentRegister, u8currentBit, u8bytesno, u8bitsno;
  uint8_t u8CopyBufferSize;
  uint16_t u16currentCoil, u16coil;

  // get the first and last coil from the message
  uint16_t u16StartCoil = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ] );
  uint16_t u16Coilno = word( au8Buffer[ NB_HI ], au8Buffer[ NB_LO ] );

  // put the number of bytes in the outcoming message
  u8bytesno = (uint8_t) (u16Coilno / 8);
  if (u16Coilno % 8 != 0) u8bytesno ++;
  au8Buffer[ ADD_HI ]  = u8bytesno;
  u8BufferSize         = ADD_LO;

  // read each coil from the register map and put its value inside the outcoming message
  u8bitsno = 0;

  for (u16currentCoil = 0; u16currentCoil < u16Coilno; u16currentCoil++) {
    u16coil = u16StartCoil + u16currentCoil;
    u8currentRegister = (uint8_t) (u16coil / 16);
    u8currentBit = (uint8_t) (u16coil % 16);

    bitWrite(
    au8Buffer[ u8BufferSize ],
    u8bitsno,
    bitRead( regs[ u8currentRegister ], u8currentBit ) );
    u8bitsno ++;

    if (u8bitsno > 7) {
      u8bitsno = 0;
      u8BufferSize++;
    }
  }

  // send outcoming message
  if (u16Coilno % 8 != 0) u8BufferSize ++;
  u8CopyBufferSize = u8BufferSize +2;
  sendTxBuffer();
  return u8CopyBufferSize;
}

int8_t Modbus::process_FC3( uint16_t *regs, uint8_t u8size ) {

  uint8_t u8StartAdd = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ] );
  uint8_t u8regsno = word( au8Buffer[ NB_HI ], au8Buffer[ NB_LO ] );
  uint8_t u8CopyBufferSize;
  uint8_t i;

  au8Buffer[ 2 ]       = u8regsno * 2;
  u8BufferSize         = 3;

  for (i = u8StartAdd; i < u8StartAdd + u8regsno; i++) {
    au8Buffer[ u8BufferSize ] = highByte(regs[i]);
    u8BufferSize++;
    au8Buffer[ u8BufferSize ] = lowByte(regs[i]);
    u8BufferSize++;
  }
  u8CopyBufferSize = u8BufferSize +2;
  sendTxBuffer();

  return u8CopyBufferSize;
}


int8_t Modbus::process_FC5( uint16_t *regs, uint8_t u8size ) {
  uint8_t u8currentRegister, u8currentBit;
  uint8_t u8CopyBufferSize;
  uint16_t u16coil = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ] );

  // point to the register and its bit
  u8currentRegister = (uint8_t) (u16coil / 16);
  u8currentBit = (uint8_t) (u16coil % 16);

  // write to coil
  bitWrite(
  regs[ u8currentRegister ],
  u8currentBit,
  au8Buffer[ NB_HI ] == 0xff );


  // send answer to master
  u8BufferSize = 6;
  u8CopyBufferSize = u8BufferSize +2;
  sendTxBuffer();

  return u8CopyBufferSize;

}


int8_t Modbus::process_FC6( uint16_t *regs, uint8_t u8size ) {

  uint8_t u8add = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ] );
  uint8_t u8CopyBufferSize;
  uint16_t u16val = word( au8Buffer[ NB_HI ], au8Buffer[ NB_LO ] );

  regs[ u8add ] = u16val;

  // keep the same header
  u8BufferSize         = RESPONSE_SIZE;

  u8CopyBufferSize = u8BufferSize +2;
  sendTxBuffer();

  return u8CopyBufferSize;
}


int8_t Modbus::process_FC15( uint16_t *regs, uint8_t u8size ) {
  uint8_t u8currentRegister, u8currentBit, u8frameByte, u8bitsno;
  uint8_t u8CopyBufferSize;
  uint16_t u16currentCoil, u16coil;
  boolean bTemp;

  // get the first and last coil from the message
  uint16_t u16StartCoil = word( au8Buffer[ ADD_HI ], au8Buffer[ ADD_LO ] );
  uint16_t u16Coilno = word( au8Buffer[ NB_HI ], au8Buffer[ NB_LO ] );


  // read each coil from the register map and put its value inside the outcoming message
  u8bitsno = 0;
  u8frameByte = 7;
  for (u16currentCoil = 0; u16currentCoil < u16Coilno; u16currentCoil++) {

    u16coil = u16StartCoil + u16currentCoil;
    u8currentRegister = (uint8_t) (u16coil / 16);
    u8currentBit = (uint8_t) (u16coil % 16);

    bTemp = bitRead(
    au8Buffer[ u8frameByte ],
    u8bitsno );

    bitWrite(
    regs[ u8currentRegister ],
    u8currentBit,
    bTemp );

    u8bitsno ++;

    if (u8bitsno > 7) {
      u8bitsno = 0;
      u8frameByte++;
    }
  }

  // send outcoming message
  // it's just a copy of the incomping frame until 6th byte
  u8BufferSize         = 6;
  u8CopyBufferSize = u8BufferSize +2;
  sendTxBuffer();
  return u8CopyBufferSize;
}


int8_t Modbus::process_FC16( uint16_t *regs, uint8_t u8size ) {
  uint8_t u8func = au8Buffer[ FUNC ];  // get the original FUNC code
  uint8_t u8StartAdd = au8Buffer[ ADD_HI ] << 8 | au8Buffer[ ADD_LO ];
  uint8_t u8regsno = au8Buffer[ NB_HI ] << 8 | au8Buffer[ NB_LO ];
  uint8_t u8CopyBufferSize;
  uint8_t i;
  uint16_t temp;

  // build header
  au8Buffer[ NB_HI ]   = 0;
  au8Buffer[ NB_LO ]   = u8regsno;
  u8BufferSize         = RESPONSE_SIZE;

  // write registers
  for (i = 0; i < u8regsno; i++) {
    temp = word(
    au8Buffer[ (BYTE_CNT + 1) + i * 2 ],
    au8Buffer[ (BYTE_CNT + 2) + i * 2 ]);

    regs[ u8StartAdd + i ] = temp;
  }
  u8CopyBufferSize = u8BufferSize +2;
  sendTxBuffer();

  return u8CopyBufferSize;
}

my main code

Code:

#define ID   1
#include<math.h>


Modbus slave(ID, 0, 0);
boolean led;
int8_t state = 0;
unsigned long tempus;
// data array for modbus network sharing
uint16_t au16data[9];

double  latitude=13.08;
static int Sensor_Value;
float Yvoltage;
static float ARDUINO_ANALOG_SCALING = 0.00488758;
static float Ydegree;


void setup() {
  // define i/o
  pinMode(2, INPUT);
  pinMode(3, INPUT);
  pinMode(4, INPUT);
  pinMode(5, INPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(13, OUTPUT);

  digitalWrite(6, LOW );
  digitalWrite(7, LOW );
  digitalWrite(8, LOW );
  digitalWrite(9, LOW );
  digitalWrite(13, HIGH );
  

  // start communication
  slave.begin( 9600 );

  tempus = millis() + 100;
  digitalWrite(13, HIGH );
}


void loop() {
  // poll messages
  // blink led pin on each valid message
  state = slave.poll( au16data, 9 );
  if (state > 4) {
    tempus = millis() + 50;
    digitalWrite(13, HIGH);
  }
  if (millis() > tempus) digitalWrite(13, LOW );

  
  // read analog inputs
  
   Sensor_Value=analogRead(A3); 
  Yvoltage = Sensor_Value * ARDUINO_ANALOG_SCALING;
   Ydegree=(30*Yvoltage)-75;
/*  mySerial.println(Ydegree);
  delay(1000);*/
  au16data[0] = Sensor_Value;

  au16data[6] = slave.getInCnt();
  au16data[7] = slave.getOutCnt();
  au16data[8] = slave.getErrCnt();
}

**anduril462** · 04-09-2014

Originally Posted by AJITnayak

1) I have value latitude 13.08. Here 13 should put in lower byte of word and 08 into higher order of byte address. How to assign it

This is answered in your other thread: Seprating floating value

Originally Posted by AJITnayak

2)i have analog sensor which read analog voltage 0-5v . that being converted from +75 deg to -75 degree.
from 0-75 degree i can read value properly on QMODBUS, But 0 to -75 master varying with 65561 value.How to covert it to -ve value.

Could you please explain more clearly and give more details? I'm not totally sure what exactly the problem is. Your equation seems a bit strange, multiplying Yvoltage by 30. Also,

Originally Posted by AJITnayak

3) IS it possible to assign our own slave address in below code

I think so. Just use the right slave ID in the constructor.

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