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ModbusRtu.h
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ModbusRtu.h
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/**
* @file ModbusRtu.h
* @version 1.21
* @date 2016.02.21
* @author Samuel Marco i Armengol
* @contact sammarcoarmengol@gmail.com
* @contribution Helium6072
*
* @description
* Arduino library for communicating with Modbus devices
* over RS232/USB/485 via RTU protocol.
*
* Further information:
* http://modbus.org/
* http://modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
*
* @license
* 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; version
* 2.1 of the License.
*
* 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
*
* @defgroup setup Modbus Object Instantiation/Initialization
* @defgroup loop Modbus Object Management
* @defgroup buffer Modbus Buffer Management
* @defgroup discrete Modbus Function Codes for Discrete Coils/Inputs
* @defgroup register Modbus Function Codes for Holding/Input Registers
*
*/
#include <inttypes.h>
#include "Arduino.h"
#include "Print.h"
#include <SoftwareSerial.h>
/**
* @struct modbus_t
* @brief
* Master query structure:
* This includes all the necessary fields to make the Master generate a Modbus query.
* A Master may keep several of these structures and send them cyclically or
* use them according to program needs.
*/
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
* @brief
* Indexes to telegram frame positions
*/
enum MESSAGE
{
ID = 0, //!< ID field
FUNC, //!< Function code position
ADD_HI, //!< Address high byte
ADD_LO, //!< Address low byte
NB_HI, //!< Number of coils or registers high byte
NB_LO, //!< Number of coils or registers low byte
BYTE_CNT //!< byte counter
};
/**
* @enum MB_FC
* @brief
* Modbus function codes summary.
* These are the implement function codes either for Master or for Slave.
*
* @see also fctsupported
* @see also modbus_t
*/
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,
EXC_ADDR_RANGE = 2,
EXC_REGS_QUANT = 3,
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
#define MAX_BUFFER 64 //!< maximum size for the communication buffer in bytes
/**
* @class Modbus
* @brief
* Arduino class library for communicating with Modbus devices over
* USB/RS232/485 (via RTU protocol).
*/
class Modbus
{
private:
HardwareSerial *port; //!< Pointer to Serial class object
SoftwareSerial *softPort; //!< Pointer to SoftwareSerial class object
uint8_t u8id; //!< 0=master, 1..247=slave number
uint8_t u8serno; //!< serial port: 0-Serial, 1..3-Serial1..Serial3; 4: use software serial
uint8_t u8txenpin; //!< flow control pin: 0=USB or RS-232 mode, >0=RS-485 mode
uint8_t u8state;
uint8_t u8lastError;
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 init(uint8_t u8id);
void sendTxBuffer();
int8_t getRxBuffer();
uint16_t calcCRC(uint8_t u8length);
uint8_t validateAnswer();
uint8_t validateRequest();
void get_FC1();
void get_FC3();
int8_t process_FC1( uint16_t *regs, uint8_t u8size );
int8_t process_FC3( uint16_t *regs, uint8_t u8size );
int8_t process_FC5( uint16_t *regs, uint8_t u8size );
int8_t process_FC6( uint16_t *regs, uint8_t u8size );
int8_t process_FC15( uint16_t *regs, uint8_t u8size );
int8_t process_FC16( uint16_t *regs, uint8_t u8size );
void buildException( uint8_t u8exception ); // build exception message
public:
Modbus();
Modbus(uint8_t u8id, uint8_t u8serno);
Modbus(uint8_t u8id, uint8_t u8serno, uint8_t u8txenpin);
Modbus(uint8_t u8id);
void begin(long u32speed);
void begin(SoftwareSerial *sPort, long u32speed);
void begin(long u32speed, uint8_t u8config);
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
};
/* _____PUBLIC FUNCTIONS_____________________________________________________ */
/**
* @brief
* Default Constructor for Master through Serial
*
* @ingroup setup
*/
Modbus::Modbus()
{
init(0, 0, 0);
}
/**
* @brief
* Full constructor for a Master/Slave through USB/RS232C
*
* @param u8id node address 0=master, 1..247=slave
* @param u8serno serial port used 0..3
* @ingroup setup
* @overload Modbus::Modbus(uint8_t u8id, uint8_t u8serno)
* @overload Modbus::Modbus(uint8_t u8id)
* @overload Modbus::Modbus()
*/
Modbus::Modbus(uint8_t u8id, uint8_t u8serno)
{
init(u8id, u8serno, 0);
}
/**
* @brief
* Full constructor for a Master/Slave through USB/RS232C/RS485
* It needs a pin for flow control only for RS485 mode
*
* @param u8id node address 0=master, 1..247=slave
* @param u8serno serial port used 0..3
* @param u8txenpin pin for txen RS-485 (=0 means USB/RS232C mode)
* @ingroup setup
* @overload Modbus::Modbus(uint8_t u8id, uint8_t u8serno, uint8_t u8txenpin)
* @overload Modbus::Modbus(uint8_t u8id)
* @overload Modbus::Modbus()
*/
Modbus::Modbus(uint8_t u8id, uint8_t u8serno, uint8_t u8txenpin)
{
init(u8id, u8serno, u8txenpin);
}
/**
* @brief
* Constructor for a Master/Slave through USB/RS232C via software serial
* This constructor only specifies u8id (node address) and should be only
* used if you want to use software serial instead of hardware serial.
* If you use this constructor you have to begin ModBus object by
* using "void Modbus::begin(SoftwareSerial *softPort, long u32speed)".
*
* @param u8id node address 0=master, 1..247=slave
* @ingroup setup
* @overload Modbus::Modbus(uint8_t u8id, uint8_t u8serno, uint8_t u8txenpin)
* @overload Modbus::Modbus(uint8_t u8id, uint8_t u8serno)
* @overload Modbus::Modbus()
*/
Modbus::Modbus(uint8_t u8id)
{
init(u8id);
}
/**
* @brief
* Initialize class object.
*
* Sets up the serial port using specified baud rate.
* Call once class has been instantiated, typically within setup().
*
* @see http://arduino.cc/en/Serial/Begin#.Uy4CJ6aKlHY
* @param speed baud rate, in standard increments (300..115200)
* @ingroup setup
*/
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);
if (u8txenpin > 1) // pin 0 & pin 1 are reserved for RX/TX
{
// return RS485 transceiver to transmit mode
pinMode(u8txenpin, OUTPUT);
digitalWrite(u8txenpin, LOW);
}
while(port->read() >= 0);
u8lastRec = u8BufferSize = 0;
u16InCnt = u16OutCnt = u16errCnt = 0;
}
/**
* @brief
* Initialize class object.
*
* Sets up the software serial port using specified baud rate and SoftwareSerial object.
* Call once class has been instantiated, typically within setup().
*
* @param speed *softPort, pointer to SoftwareSerial class object
* @param speed baud rate, in standard increments (300..115200)
* @ingroup setup
*/
void Modbus::begin(SoftwareSerial *sPort, long u32speed)
{
softPort=sPort;
softPort->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);
}
while(softPort->read() >= 0);
u8lastRec = u8BufferSize = 0;
u16InCnt = u16OutCnt = u16errCnt = 0;
}
/**
* @brief
* Initialize class object.
*
* Sets up the serial port using specified baud rate.
* Call once class has been instantiated, typically within setup().
*
* @see http://arduino.cc/en/Serial/Begin#.Uy4CJ6aKlHY
* @param speed baud rate, in standard increments (300..115200)
* @param config data frame settings (data length, parity and stop bits)
* @ingroup setup
*/
void Modbus::begin(long u32speed,uint8_t u8config)
{
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);
if (u8txenpin > 1) // pin 0 & pin 1 are reserved for RX/TX
{
// return RS485 transceiver to transmit mode
pinMode(u8txenpin, OUTPUT);
digitalWrite(u8txenpin, LOW);
}
while(port->read() >= 0);
u8lastRec = u8BufferSize = 0;
u16InCnt = u16OutCnt = u16errCnt = 0;
}
/**
* @brief
* Initialize default class object.
*
* Sets up the serial port using 19200 baud.
* Call once class has been instantiated, typically within setup().
*
* @overload Modbus::begin(uint16_t u16BaudRate)
* @ingroup setup
*/
void Modbus::begin()
{
begin(19200);
}
/**
* @brief
* Method to write a new slave ID address
*
* @param u8id new slave address between 1 and 247
* @ingroup setup
*/
void Modbus::setID( uint8_t u8id)
{
if (( u8id != 0) && (u8id <= 247))
{
this->u8id = u8id;
}
}
/**
* @brief
* Method to read current slave ID address
*
* @return u8id current slave address between 1 and 247
* @ingroup setup
*/
uint8_t Modbus::getID()
{
return this->u8id;
}
/**
* @brief
* Initialize time-out parameter
*
* Call once class has been instantiated, typically within setup().
* The time-out timer is reset each time that there is a successful communication
* between Master and Slave. It works for both.
*
* @param time-out value (ms)
* @ingroup setup
*/
void Modbus::setTimeOut( uint16_t u16timeOut)
{
this->u16timeOut = u16timeOut;
}
/**
* @brief
* Return communication Watchdog state.
* It could be usefull to reset outputs if the watchdog is fired.
*
* @return TRUE if millis() > u32timeOut
* @ingroup loop
*/
boolean Modbus::getTimeOutState()
{
return (millis() > u32timeOut);
}
/**
* @brief
* Get input messages counter value
* This can be useful to diagnose communication
*
* @return input messages counter
* @ingroup buffer
*/
uint16_t Modbus::getInCnt()
{
return u16InCnt;
}
/**
* @brief
* Get transmitted messages counter value
* This can be useful to diagnose communication
*
* @return transmitted messages counter
* @ingroup buffer
*/
uint16_t Modbus::getOutCnt()
{
return u16OutCnt;
}
/**
* @brief
* Get errors counter value
* This can be useful to diagnose communication
*
* @return errors counter
* @ingroup buffer
*/
uint16_t Modbus::getErrCnt()
{
return u16errCnt;
}
/**
* Get modbus master state
*
* @return = 0 IDLE, = 1 WAITING FOR ANSWER
* @ingroup buffer
*/
uint8_t Modbus::getState()
{
return u8state;
}
/**
* Get the last error in the protocol processor
*
* @returnreturn NO_REPLY = 255 Time-out
* @return EXC_FUNC_CODE = 1 Function code not available
* @return EXC_ADDR_RANGE = 2 Address beyond available space for Modbus registers
* @return EXC_REGS_QUANT = 3 Coils or registers number beyond the available space
* @ingroup buffer
*/
uint8_t Modbus::getLastError()
{
return u8lastError;
}
/**
* @brief
* *** Only Modbus Master ***
* Generate a query to an slave with a modbus_t telegram structure
* The Master must be in COM_IDLE mode. After it, its state would be COM_WAITING.
* This method has to be called only in loop() section.
*
* @see modbus_t
* @param modbus_t modbus telegram structure (id, fct, ...)
* @ingroup loop
* @todo finish function 15
*/
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: // TODO: implement "sending 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;
}
/**
* @brief *** Only for Modbus Master ***
* This method checks if there is any incoming answer if pending.
* If there is no answer, it would change Master state to COM_IDLE.
* This method must be called only at loop section.
* Avoid any delay() function.
*
* Any incoming data would be redirected to au16regs pointer,
* as defined in its modbus_t query telegram.
*
* @params nothing
* @return errors counter
* @ingroup loop
*/
int8_t Modbus::poll()
{
// check if there is any incoming frame
uint8_t u8current;
if(u8serno<4)
u8current = port->available();
else
u8current = softPort->available();
if (millis() > u32timeOut)
{
u8state = COM_IDLE;
u8lastError = NO_REPLY;
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;
}
/**
* @brief
* *** Only for Modbus Slave ***
* This method checks if there is any incoming query
* Afterwards, it would shoot a validation routine plus a register query
* Avoid any delay() function !!!!
* After a successful frame between the Master and the Slave, the time-out timer is reset.
*
* @param *regs register table for communication exchange
* @param u8size size of the register table
* @return 0 if no query, 1..4 if communication error, >4 if correct query processed
* @ingroup loop
*/
int8_t Modbus::poll( uint16_t *regs, uint8_t u8size )
{
au16regs = regs;
u8regsize = u8size;
uint8_t u8current;
// check if there is any incoming frame
if(u8serno<4)
u8current = port->available();
else
u8current = softPort->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();
u8lastError = i8state;
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();
}
u8lastError = u8exception;
return u8exception;
}
u32timeOut = millis() + long(u16timeOut);
u8lastError = 0;
// 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;
}
return i8state;
}
/* _____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;
}
void Modbus::init(uint8_t u8id)
{
this->u8id = u8id;
this->u8serno = 4;
this->u8txenpin = 0;
this->u16timeOut = 1000;
}
/**
* @brief
* This method moves Serial buffer data to the Modbus au8Buffer.
*
* @return buffer size if OK, ERR_BUFF_OVERFLOW if u8BufferSize >= MAX_BUFFER
* @ingroup buffer
*/
int8_t Modbus::getRxBuffer()
{
boolean bBuffOverflow = false;
if (u8txenpin > 1) digitalWrite( u8txenpin, LOW );
u8BufferSize = 0;
if(u8serno<4)
while ( port->available() )
{
au8Buffer[ u8BufferSize ] = port->read();
u8BufferSize ++;
if (u8BufferSize >= MAX_BUFFER) bBuffOverflow = true;
}
else
while ( softPort->available() )
{
au8Buffer[ u8BufferSize ] = softPort->read();
u8BufferSize ++;
if (u8BufferSize >= MAX_BUFFER) bBuffOverflow = true;
}
u16InCnt++;
if (bBuffOverflow)
{
u16errCnt++;
return ERR_BUFF_OVERFLOW;
}
return u8BufferSize;
}
/**
* @brief
* This method transmits au8Buffer to Serial line.
* Only if u8txenpin != 0, there is a flow handling in order to keep
* the RS485 transceiver in output state as long as the message is being sent.
* This is done with UCSRxA register.
* The CRC is appended to the buffer before starting to send it.
*
* @param nothing
* @return nothing
* @ingroup buffer
*/
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
if(u8serno<4)
port->write( au8Buffer, u8BufferSize );
else
softPort->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 );
}
if(u8serno<4)
while(port->read() >= 0);
else
while(softPort->read() >= 0);
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;