#include <slave.h>

Inheritance diagram for Modbus::Slave:

Public Member Functions
int	dataAddress (int addr) const
	returns the address in the MODBUS data model corresponding to a PDU address. More...

Device *	device () const
	returns the device used to access the network

bool	isOpen () const
	returns true if isValid() and device() is opened.

bool	isValid () const
	returns true if device() and number() are sets

int	number () const
	Get slave number. More...

int	pduAddress (int addr) const
	returns the PDU address corresponding to an address in the MODBUS data model. More...

bool	pduAddressing () const
	Modbus addressing mode. More...

int	readCoil (int addr, bool &dest)
	Read a single coil (bit) More...

virtual int	readCoils (int addr, bool *dest, int nb=1)
	Read many coils (bits) More...

int	readDiscreteInput (int addr, bool &dest)
	Read a single discrete input (input bit) More...

virtual int	readDiscreteInputs (int addr, bool *dest, int nb=1)
	Read many discrete inputs (input bits) More...

int	readInputRegister (int addr, uint16_t &dest)
	Read a single input register. More...

template<typename T , Endian e>
int	readInputRegister (int addr, Data< T, e > &dest)
	Read a single input data. More...

virtual int	readInputRegisters (int addr, uint16_t *dest, int nb=1)
	Read many input registers. More...

template<typename T , Endian e>
int	readInputRegisters (int addr, Data< T, e > *dest, int nb=1)
	Read many input data. More...

int	readRegister (int addr, uint16_t &dest)
	Read a single register. More...

template<typename T , Endian e>
int	readRegister (int addr, Data< T, e > &dest)
	Read a single holding data. More...

virtual int	readRegisters (int addr, uint16_t *dest, int nb=1)
	Read many registers. More...

template<typename T , Endian e>
int	readRegisters (int addr, Data< T, e > *dest, int nb=1)
	Read many holding data. More...

virtual int	reportSlaveId (uint16_t max_dest, uint8_t *dest)
	returns a description of the controller More...

template<typename T , Endian e = EndianBig>
int	reportSlaveId (SlaveReport< T, e > &dest)
	returns a description of the controller More...

void	setDevice (Device *dev)
	Sets the device used to access the network.

void	setNumber (int n)
	Sets the slave number.

void	setPduAddressing (bool pduAddressing=true)
	Set the Modbus addressing mode. More...

	Slave (int slaveAddr, Device *dev)
	Constructor.

	Slave ()
	Default Constructor. More...

virtual int	writeCoil (int addr, bool src)
	Write a single coil (bit) More...

virtual int	writeCoils (int addr, const bool *src, int nb)
	Write many coils (bits) More...

virtual int	writeReadRegisters (int write_addr, const uint16_t src, int write_nb, int read_addr, uint16_t dest, int read_nb)
	Write and read many registers in a single transaction. More...

virtual int	writeRegister (int addr, uint16_t value)
	Write a single register. More...

template<typename T , Endian e>
int	writeRegister (int addr, Data< T, e > &value)
	Write a single holding data. More...

virtual int	writeRegisters (int addr, const uint16_t *src, int nb)
	Write many registers. More...

template<typename T , Endian e>
int	writeRegisters (int addr, Data< T, e > *src, int nb=1)
	Write many holding data. More...

virtual	~Slave ()
	Destructor. More...

Static Public Member Functions
static void	setBoolArray (bool dest, const uint8_t src, size_t n)
	Set many booleans from an array of bytes. More...

Detailed Description

Slave connected to Modbus.

Author: Pascal JEAN, aka epsilonrt

Copyright: GNU Lesser General Public License

Examples:: master/read-coils/main.cpp, master/read-holding-data/main.cpp, master/read-input-registers/main.cpp, master/report-slave-id/main.cpp, master/rw-holding-json/main.cpp, and master/write-holding-data/main.cpp.

Constructor & Destructor Documentation

◆ Slave()

Modbus::Slave::Slave ( )

Default Constructor.

object cannot be used without calling setDevice() and setNumber()

Referenced by reportSlaveId().

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◆ ~Slave()

virtual Modbus::Slave::~Slave ( )

virtual

Destructor.

The destructor closes the connection if it is open and releases all affected resources.

Member Function Documentation

◆ dataAddress()

int Modbus::Slave::dataAddress ( int addr ) const

returns the address in the MODBUS data model corresponding to a PDU address.

If the PDU addressing mode is not enabled (which is the case by default), the data model address is equal to the PDU address plus 1, otherwise they are equal.

◆ number()

int Modbus::Slave::number ( ) const

Get slave number.

This function shall get the slave number.

Returns: the slave number

Examples:: master/read-coils/main.cpp, master/read-holding-data/main.cpp, master/read-input-registers/main.cpp, master/report-slave-id/main.cpp, master/rw-holding-json/main.cpp, master/write-holding-data/main.cpp, server/clock-server-json/main.cpp, and server/clock-server/main.cpp.

◆ pduAddress()

int Modbus::Slave::pduAddress ( int addr ) const

returns the PDU address corresponding to an address in the MODBUS data model.

If the PDU addressing mode is not enabled (which is the case by default), the PDU address is equal to the MODBUS address minus 1, otherwise they are equal.

◆ pduAddressing()

bool Modbus::Slave::pduAddressing ( ) const

Modbus addressing mode.

This function shall return the Modbus addressing mode used. The address mode used is, by default, that of the data model, that is to say, a numbering of the registers from 1 to n.

The Modbus application protocol defines precisely PDU addressing rules. In a Modbus PDU each data is addressed from 0 to 65535.

It also defines clearly a Modbus data model composed of 4 blocks that comprises several elements numbered from 1 to n.

In the Modbus data Model each element within a data block is numbered from 1 to n.

Afterwards the Modbus data model has to be bound to the device application (IEC -61131 object, or other application model).

Returns: true for Modbus PDU adressing

See also: setPduAddressing()

◆ readCoil()

int Modbus::Slave::readCoil	(	int	addr,
		bool &	dest
	)

inline

Read a single coil (bit)

This function shall read a signle bit (coil) to the address addr of the device. The result of reading is stored in dest as boolean.

The function uses the Modbus function code 0x01 (read coil status).

Returns: 1 if successful. Otherwise it shall return -1 and set errno.

Examples:: server/clock-server-json/main.cpp, and server/clock-server/main.cpp.

References readCoils().

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◆ readCoils()

virtual int Modbus::Slave::readCoils	(	int	addr,
		bool *	dest,
		int	nb = `1`
	)

virtual

Read many coils (bits)

This function shall read the status of the nb bits (coils) to the address addr of the remote device. The result of reading is stored in dest array as boolean.

The function uses the Modbus function code 0x01 (read coil status).

Returns: the number of read bits if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

Examples:: master/read-coils/main.cpp.

Referenced by readCoil().

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◆ readDiscreteInput()

int Modbus::Slave::readDiscreteInput	(	int	addr,
		bool &	dest
	)

inline

Read a single discrete input (input bit)

This function shall read a single input bits to the address addr of the device. The result of reading is stored in dest as boolean.

The function uses the Modbus function code 0x02 (read input status).

Returns: 1 if successful. Otherwise it shall return -1 and set errno.

References readDiscreteInputs().

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◆ readDiscreteInputs()

virtual int Modbus::Slave::readDiscreteInputs	(	int	addr,
		bool *	dest,
		int	nb = `1`
	)

virtual

Read many discrete inputs (input bits)

This function shall read the content of the nb input bits to the address addr of the remote device. The result of reading is stored in dest array as boolean.

The function uses the Modbus function code 0x02 (read input status).

Returns: the number of read input status if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

Referenced by readDiscreteInput().

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◆ readInputRegister() [1/2]

int Modbus::Slave::readInputRegister	(	int	addr,
		uint16_t &	dest
	)

inline

Read a single input register.

This function shall read a single input register to the address addr of the device.

The result of reading is stored in dest as word values (16 bits).

The function uses the Modbus function code 0x04 (read input registers). The holding registers and input registers have different historical meaning, but nowadays it's more common to use holding registers only.

Returns: 1 if successful. Otherwise it shall return -1 and set errno.

References readInputRegisters().

Referenced by Modbus::BufferedSlave::writeInputRegister().

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◆ readInputRegister() [2/2]

template<typename T , Endian e>

int Modbus::Slave::readInputRegister	(	int	addr,
		Data< T, e > &	dest
	)

inline

Read a single input data.

Data is a template class for storing, transmitting, and receiving arithmetic data in multiple 16-bit Modbus registers.

This function shall read a single input data to the address addr of the device.

The result of reading is stored in dest as T value.

The function uses the Modbus function code 0x04 (read input registers).

Returns: return the number of read input Modbus registers (16-bit) if successful. Otherwise it shall return -1 and set errno.

References readInputRegisters(), and Modbus::Data< T, e >::registers().

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◆ readInputRegisters() [1/2]

virtual int Modbus::Slave::readInputRegisters	(	int	addr,
		uint16_t *	dest,
		int	nb = `1`
	)

virtual

Read many input registers.

This function shall read the content of the nb input registers to the address addr of the remote device.

The result of reading is stored in dest array as word values (16 bits).

The function uses the Modbus function code 0x04 (read input registers). The holding registers and input registers have different historical meaning, but nowadays it's more common to use holding registers only.

Returns: return the number of read input registers if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

Examples:: master/read-input-registers/main.cpp.

Referenced by readInputRegister(), readInputRegisters(), and Modbus::BufferedSlave::writeInputRegister().

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◆ readInputRegisters() [2/2]

template<typename T , Endian e>

int Modbus::Slave::readInputRegisters	(	int	addr,
		Data< T, e > *	dest,
		int	nb = `1`
	)

inline

Read many input data.

Data is a template class for storing, transmitting, and receiving arithmetic data in multiple 16-bit Modbus registers.

This function shall read the content of the nb input data to the address addr of the device.

The result of reading is stored in dest array as T values.

The function uses the Modbus function code 0x04 (read input registers).

Returns: return the number of read input Modbus registers (16-bit) if successful. Otherwise it shall return -1 and set errno.

References readInputRegisters().

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◆ readRegister() [1/2]

int Modbus::Slave::readRegister	(	int	addr,
		uint16_t &	dest
	)

inline

Read a single register.

This function shall read a signle holding register to the address addr of the device.

The result of reading is stored in dest as word values (16 bits).

The function uses the Modbus function code 0x03 (read holding registers).

Returns: 1 if successful. Otherwise it shall return -1 and set errno.

Examples:: server/clock-server-json/main.cpp, and server/clock-server/main.cpp.

References readRegisters().

Referenced by Modbus::BufferedSlave::writeInputRegister().

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◆ readRegister() [2/2]

template<typename T , Endian e>

int Modbus::Slave::readRegister	(	int	addr,
		Data< T, e > &	dest
	)

inline

Read a single holding data.

Data is a template class for storing, transmitting, and receiving arithmetic data in multiple 16-bit Modbus registers.

This function shall read a single holding data to the address addr of the device.

The result of reading is stored in dest as T value.

The function uses the Modbus function code 0x03 (read holding registers).

Returns: return the number of read holding Modbus registers (16-bit) if successful. Otherwise it shall return -1 and set errno.

References readRegisters(), and Modbus::Data< T, e >::registers().

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◆ readRegisters() [1/2]

virtual int Modbus::Slave::readRegisters	(	int	addr,
		uint16_t *	dest,
		int	nb = `1`
	)

virtual

Read many registers.

This function shall read the content of the nb holding registers to the address addr of the remote device.

The result of reading is stored in dest array as word values (16 bits).

The function uses the Modbus function code 0x03 (read holding registers).

Returns: return the number of read registers if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

Examples:: master/read-holding-data/main.cpp, and master/rw-holding-json/main.cpp.

Referenced by readRegister(), readRegisters(), and Modbus::BufferedSlave::writeInputRegister().

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◆ readRegisters() [2/2]

template<typename T , Endian e>

int Modbus::Slave::readRegisters	(	int	addr,
		Data< T, e > *	dest,
		int	nb = `1`
	)

inline

Read many holding data.

Data is a template class for storing, transmitting, and receiving arithmetic data in multiple 16-bit Modbus registers.

This function shall read the content of the nb data to the address addr of the device.

The result of reading is stored in dest array as T values.

The function uses the Modbus function code 0x03 (read holding registers).

Returns: return the number of read holding Modbus registers (16-bit) if successful. Otherwise it shall return -1 and set errno.

References readRegisters().

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◆ reportSlaveId() [1/2]

virtual int Modbus::Slave::reportSlaveId	(	uint16_t	max_dest,
		uint8_t *	dest
	)

virtual

returns a description of the controller

This function shall send a request to the controller to obtain a description of the controller.

The response stored in dest contains:

the slave ID, this unique ID is in reality not unique at all so it’s not possible to depend on it to know how the information are packed in the response.
the run indicator status (0x00 = OFF, 0xFF = ON)
additional data specific to each controller. For example, libmodbuspp returns the version of the library as a string.

The function writes at most max_dest bytes from the response to dest so you must ensure that dest is large enough.

Returns: return the number of read data if successful. If the output was truncated due to the max_dest limit then the return value is the number of bytes which would have been written to dest if enough space had been available. Thus, a return value greater than max_dest means that the response data was truncated. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

Examples:: master/report-slave-id/main.cpp.

Referenced by reportSlaveId(), Modbus::BufferedSlave::writeInputRegister(), and writeRegister().

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◆ reportSlaveId() [2/2]

template<typename T , Endian e = EndianBig>

int Modbus::Slave::reportSlaveId ( SlaveReport< T, e > & dest )

inline

returns a description of the controller

SlaveReport is a template class for storing and manipulate slave identifier datas returns by the MODBUS 17 function.

Parameters

dest	description of the controller

Returns: return the number of read data bytes if successful. Otherwise it shall return -1 and set errno.

References reportSlaveId(), and Slave().

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◆ setBoolArray()

static void Modbus::Slave::setBoolArray	(	bool *	dest,
		const uint8_t *	src,
		size_t	n
	)

static

Set many booleans from an array of bytes.

All the bits of the bytes read from the first position of the array src are written as booleans in the dest array.

Parameters

dest
src
n

Referenced by writeRegister().

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◆ setPduAddressing()

void Modbus::Slave::setPduAddressing ( bool pduAddressing = true )

Set the Modbus addressing mode.

Parameters

pduAddressing true for Modbus PDU adressing

See also: pduAddressing()

◆ writeCoil()

virtual int Modbus::Slave::writeCoil	(	int	addr,
		bool	src
	)

virtual

Write a single coil (bit)

This function shall write the status of src at the address addr of the remote device.

The function uses the Modbus function code 0x05 (force single coil).

Returns: 1 if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

◆ writeCoils()

virtual int Modbus::Slave::writeCoils	(	int	addr,
		const bool *	src,
		int	nb
	)

virtual

Write many coils (bits)

This function shall write the status of the nb bits (coils) from src at the address addr of the remote device. The src array must contains booelans.

The function uses the Modbus function code 0x0F (force multiple coils).

Returns: the number of written bits if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

◆ writeReadRegisters()

virtual int Modbus::Slave::writeReadRegisters	(	int	write_addr,
		const uint16_t *	src,
		int	write_nb,
		int	read_addr,
		uint16_t *	dest,
		int	read_nb
	)

virtual

Write and read many registers in a single transaction.

This function shall write the content of the write_nb holding registers from the array 'src' to the address write_addr of the remote device then shall read the content of the read_nb holding registers to the address read_addr of the remote device. The result of reading is stored in dest array as word values (16 bits).

You must take care to allocate enough memory to store the results in dest (at least nb * sizeof(uint16_t)).

The function uses the Modbus function code 0x17 (write/read registers).

Returns: the number of read registers if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

◆ writeRegister() [1/2]

virtual int Modbus::Slave::writeRegister	(	int	addr,
		uint16_t	value
	)

virtual

Write a single register.

This function shall write the value of value holding registers at the address addr of the remote device.

The function uses the Modbus function code 0x06 (preset single register).

Returns: 1 if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

Referenced by Modbus::BufferedSlave::writeInputRegister().

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◆ writeRegister() [2/2]

template<typename T , Endian e>

int Modbus::Slave::writeRegister	(	int	addr,
		Data< T, e > &	value
	)

inline

Write a single holding data.

Data is a template class for storing, transmitting, and receiving arithmetic data in multiple 16-bit Modbus registers.

This function shall write a single holding data from value at address addr of the device.

The function uses the Modbus function code 0x10 (preset multiple registers).

Returns: number of written holding Modbus registers (16-bit) if successful. Otherwise it shall return -1 and set errno.

References Modbus::Data< T, e >::registers(), reportSlaveId(), setBoolArray(), and writeRegisters().

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◆ writeRegisters() [1/2]

virtual int Modbus::Slave::writeRegisters	(	int	addr,
		const uint16_t *	src,
		int	nb
	)

virtual

Write many registers.

This function shall write the content of the nb holding registers from the array src at address addr of the remote device.

The function uses the Modbus function code 0x10 (preset multiple registers).

Returns: number of written registers if successful. Otherwise it shall return -1 and set errno.

Reimplemented in Modbus::BufferedSlave.

Examples:: master/rw-holding-json/main.cpp, and master/write-holding-data/main.cpp.

Referenced by Modbus::BufferedSlave::writeInputRegister(), writeRegister(), and writeRegisters().

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◆ writeRegisters() [2/2]

template<typename T , Endian e>

int Modbus::Slave::writeRegisters	(	int	addr,
		Data< T, e > *	src,
		int	nb = `1`
	)

inline

Write many holding data.

Data is a template class for storing, transmitting, and receiving arithmetic data in multiple 16-bit Modbus registers.

This function shall write the content of the nb holding data from the array src at address addr of the device.

The function uses the Modbus function code 0x10 (preset multiple registers).

Returns: number of written holding Modbus registers (16-bit) if successful. Otherwise it shall return -1 and set errno.

References writeRegisters().

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Public Member Functions

Static Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ Slave()

◆ ~Slave()

Member Function Documentation

◆ dataAddress()

◆ number()

◆ pduAddress()

◆ pduAddressing()

◆ readCoil()

◆ readCoils()

◆ readDiscreteInput()

◆ readDiscreteInputs()

◆ readInputRegister() [1/2]

◆ readInputRegister() [2/2]

◆ readInputRegisters() [1/2]

◆ readInputRegisters() [2/2]

◆ readRegister() [1/2]

◆ readRegister() [2/2]

◆ readRegisters() [1/2]

◆ readRegisters() [2/2]

◆ reportSlaveId() [1/2]

◆ reportSlaveId() [2/2]

◆ setBoolArray()

◆ setPduAddressing()

◆ writeCoil()

◆ writeCoils()

◆ writeReadRegisters()

◆ writeRegister() [1/2]

◆ writeRegister() [2/2]

◆ writeRegisters() [1/2]

◆ writeRegisters() [2/2]