MbusSerialServerBase Class Reference

This base class implements common functionality for both serial Modbus protocols. More...

Public Types
enum	{ SER_DATABITS_7 = 7, SER_DATABITS_8 = 8 }
enum	{ SER_STOPBITS_1 = 1, SER_STOPBITS_2 = 2 }
enum	{ SER_PARITY_NONE = 0, SER_PARITY_EVEN = 2, SER_PARITY_ODD = 1 }

Public Member Functions
virtual int	startupServer (const char *const portName, long baudRate, int dataBits, int stopBits, int parity)
	Puts the Modbus server into operation. More...
void	shutdownServer ()
	Shuts down the Modbus server. More...
int	isStarted ()
	Returns whether server has been started up. More...
virtual int	enableRs485Mode (int rtsDelay)
	Enables RS485 mode. More...
int	addDataTable (int slaveAddr, MbusDataTableInterface *dataTablePtr)
	Associates a protocol object with a Data Provider and a Modbus slave ID. More...
virtual int	serverLoop ()=0
	Modbus slave server loop. More...
int	getConnectionStatus ()
	Checks if a Modbus master is polling periodically. More...

Static Public Member Functions
static const TCHAR *	getPackageVersion ()
	Returns the library version number. More...

Protocol Configuration
int	setTimeout (long timeOut)
	Configures master activity time-out supervision. More...
long	getTimeout ()
	Returns the currently set master activity time-out value. More...
void	disableExceptionReplies ()
	Supress exception replies to be sent. More...
void	enableExceptionReplies ()
	Enables exception replies after they have been turned off. More...

Transmission Statistic Functions
unsigned long	getTotalCounter ()
	Returns how often a message transfer has been executed. More...
void	resetTotalCounter ()
	Resets total message transfer counter.
unsigned long	getSuccessCounter ()
	Returns how often a message transfer was successful. More...
void	resetSuccessCounter ()
	Resets successful message transfer counter.

Detailed Description

This base class implements common functionality for both serial Modbus protocols.

These methods apply to RTU and ASCII protocol flavours via inheritance.

See also

Server Functions common to all Modbus Protocol Flavours, Serial Protocols

MbusDataTableInterface, MbusRtuSlaveProtocol, MbusAsciiSlaveProtocol, MbusTcpSlaveProtocol

Member Enumeration Documentation

anonymous enum

anonymous enum

Enumerator
SER_DATABITS_7	7 data bits
SER_DATABITS_8	8 data bits

anonymous enum

anonymous enum

Enumerator
SER_STOPBITS_1	1 stop bit
SER_STOPBITS_2	2 stop bits

anonymous enum

anonymous enum

Enumerator
SER_PARITY_NONE	No parity.
SER_PARITY_EVEN	Even parity.
SER_PARITY_ODD	Odd parity.

Member Function Documentation

startupServer()

int startupServer ( const char *const  portName, long  baudRate, int  dataBits, int  stopBits, int  parity  )

virtual

Puts the Modbus server into operation.

This function opens the serial port. After the port has been opened queries from a Modbus master will be processed.

Parameters

portName	Serial port identifier (e.g. "COM1", "/dev/ser1 or /dev/ttyS0")
baudRate	The port baudRate in bps (typically 1200 - 115200, maximum value depends on UART hardware)
dataBits	Must be SER_DATABITS_8 for RTU
stopBits	SER_STOPBITS_1: 1 stop bit, SER_STOPBITS_2: 2 stop bits
parity	SER_PARITY_NONE: no parity, SER_PARITY_ODD: odd parity, SER_PARITY_EVEN: even parity

Note

The Modbus standard requires two stop bits if no parity is chosen. This library is not enforcing this but it is a recommended configuration.

Returns

FTALK_SUCCESS on success or error code. See Error Management for a list of error codes.

Reimplemented in MbusRtuSlaveProtocol.

References FTALK_ILLEGAL_ARGUMENT_ERROR, FTALK_ILLEGAL_SLAVE_ADDRESS, FTALK_ILLEGAL_STATE_ERROR, FTALK_NO_DATA_TABLE_ERROR, FTALK_OPEN_ERR, FTALK_PORT_ALREADY_OPEN, FTALK_PORT_NO_ACCESS, FTALK_SUCCESS, and isStarted().

shutdownServer()

void shutdownServer ( )

virtual

Shuts down the Modbus server.

This function also closes any associated communication resources like serial ports or sockets.

Implements MbusSlaveServer.

isStarted()

int isStarted ( )

virtual

Returns whether server has been started up.

Return values

true	= started
false	= shutdown

Implements MbusSlaveServer.

enableRs485Mode()

int enableRs485Mode ( int  rtsDelay )

virtual

Enables RS485 mode.

In RS485 mode the RTS signal can be used to enable and disable the transmitter of a RS232/RS485 converter. The RTS signal is asserted before sending data. It is cleared after the transmit buffer has been emptied and in addition the specified delay time has elapsed. The delay time is necessary because even the transmit buffer is already empty, the UART's FIFO will still contain unsent characters.

Warning

The use of RTS controlled RS232/RS485 converters should be avoided if possible. It is difficult to determine the exact time when to switch off the transmitter with non real-time operating systems like Windows and Linux. If it is switched off to early characters might still sit in the FIFO or the transmit register of the UART and these characters will be lost. Hence the slave will not recognize the message. On the other hand if it is switched off too late then the slave's message is corrupted and the master will not recognize the message.

Remarks

The delay value is indicative only and not guaranteed to be maintained. How precise it is followed depends on the operating system used, it's scheduling priority and it's system timer resolution.

Note

This mode must be set before starting the server in order to come into effect.

Parameters

rtsDelay

Delay time in ms (Range: 0 - 100000) which applies after the transmit buffer is empty. 0 disables this mode.

Return values

FTALK_SUCCESS	Success
FTALK_ILLEGAL_ARGUMENT_ERROR	Argument out of range
FTALK_ILLEGAL_STATE_ERROR	Protocol is already open

References FTALK_ILLEGAL_ARGUMENT_ERROR, FTALK_ILLEGAL_STATE_ERROR, FTALK_SUCCESS, and isStarted().

addDataTable()

int addDataTable ( int  slaveAddr, MbusDataTableInterface *  dataTablePtr  )

inherited

Associates a protocol object with a Data Provider and a Modbus slave ID.

Parameters

slaveAddr	Modbus slave address for server to listen on (-1 - 255). 0 is regarded as a valid value for a MODBUS/TCP server address. A value of -1 means the server disregards the slave address and listens to all slave addresses. 0 or -1 is only valid for MODBUS/TCP!
dataTablePtr	Modbus data table pointer. Must point to a Data Provider object derived from the MbusDataTableInterface class. The Data Provider is the interface between your application data and the Modbus network.

Returns

FTALK_SUCCESS on success or error code. See Error Management for a list of error codes.

References FTALK_ILLEGAL_ARGUMENT_ERROR, and FTALK_SUCCESS.

serverLoop()

virtual int serverLoop ( )

pure virtualinherited

Modbus slave server loop.

This server loop must be called continuously. It must not be blocked. The server has to be started before calling the serverLoop() method.

In most cases the server loop is executed in an infinite loop in its own thread:

while (notTerminated) {
  mbusProtocol.serverLoop();
}

Returns

FTALK_SUCCESS on success or error code. See Error Management for a list of error codes.

Implemented in MbusTcpSlaveProtocol, MbusRtuSlaveProtocol, MbusRtuOverTcpSlaveProtocol, MbusUdpSlaveProtocol, MbusAsciiSlaveProtocol, and MbusIpServerBase.

getConnectionStatus()

int getConnectionStatus ( )

inlineinherited

Checks if a Modbus master is polling periodically.

Return values

true	= A master is polling at a frequency higher than the master transmit time-out value
false	= No master is polling within the time-out period

Note

The master transmit time-out value must be set > 0 in order for this function to work.

setTimeout()

int setTimeout ( long  timeOut )

inherited

Configures master activity time-out supervision.

The slave can monitor whether a master is actually polling or not. This function sets the activity time-out to the specified value. A value of 0 disables the time-out, which stops time-out notifications being sent to the Data Provider. Default value is 1000 ms.

Remarks

The time-out value is a minimum value only and the actual time may be longer. How precise it is followed depends on the operating system used, its scheduling priority and its system timer resolution.

Note

The time-out does not check whether a master is sending valid frames. The transmission of characters is sufficient to avoid the time-out.

Parameters

timeOut

Timeout value in ms (Range: 0 - 100000), 0 disables time-out

Return values

FTALK_SUCCESS	Success
FTALK_ILLEGAL_ARGUMENT_ERROR	Argument out of range

References FTALK_ILLEGAL_ARGUMENT_ERROR, and FTALK_SUCCESS.

getTimeout()

long getTimeout ( )

inlineinherited

Returns the currently set master activity time-out value.

Returns

Timeout value in ms

disableExceptionReplies()

void disableExceptionReplies ( )

inherited

Supress exception replies to be sent.

With this option only positive replies are sent to the master. All failure replies are silently discarded. This option can be useful if redundant Modbus devices are used. In this scenario supressing the reply would trigger a swap-over of the redundant devices.

enableExceptionReplies()

void enableExceptionReplies ( )

inherited

Enables exception replies after they have been turned off.

Sending exception replies in case of slave failures is the normal mode of operation.

getTotalCounter()

unsigned long getTotalCounter ( )

inlineinherited

Returns how often a message transfer has been executed.

Returns

Counter value

getSuccessCounter()

unsigned long getSuccessCounter ( )

inlineinherited

Returns how often a message transfer was successful.

Returns

Counter value

getPackageVersion()

const TCHAR * getPackageVersion ( )

staticinherited

Returns the library version number.

Returns

Version string