modbus

package module
v1.0.0 Latest Latest
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 Go to latest Published: Jul 11, 2024 License: BSD-3-Clause Imports: 11 Imported by: 0

README

go modbus Build Status GoDoc

Fault-tolerant, fail-fast implementation of Modbus protocol in Go.

Supported functions

Bit access:

  • Read Discrete Inputs
  • Read Coils
  • Write Single Coil
  • Write Multiple Coils

16-bit access:

  • Read Input Registers
  • Read Holding Registers
  • Write Single Register
  • Write Multiple Registers
  • Read/Write Multiple Registers
  • Mask Write Register
  • Read FIFO Queue

Supported formats

  • TCP
  • Serial (RTU, ASCII)
  • Encapsulated RTU over TCP

Usage

Basic usage:

slaveId := 0x01

// Modbus TCP
client := modbus.TCPClient("localhost:502")
// Read input register 9
results, err := client.ReadInputRegisters(slaveId, 8, 1)

// Modbus RTU/ASCII
// Default configuration is 19200, 8, 1, even
client = modbus.RTUClient("/dev/ttyS0")
results, err = client.ReadCoils(slaveId, 2, 1)

// Modbus Encapsulated RTU over TCP
client = modbus.EncClient("gateway:20108")
results, err = client.ReadCoils(slaveId, 2, 1)

Advanced usage:


slaveId := 0x01

// Modbus TCP
handler := modbus.NewTCPClientHandler("localhost:502")
handler.Timeout = 10 * time.Second
handler.Logger = log.New(os.Stdout, "test: ", log.LstdFlags)
// Connect manually so that multiple requests are handled in one connection session
err := handler.Connect()
defer handler.Close()

client := modbus.NewClient(handler)
results, err := client.ReadDiscreteInputs(slaveId, 15, 2)
results, err = client.WriteMultipleRegisters(slaveId, 1, 2, []byte{0, 3, 0, 4})
results, err = client.WriteMultipleCoils(slaveId, 5, 10, []byte{4, 3})

// Modbus RTU/ASCII
handler := modbus.NewRTUClientHandler("/dev/ttyUSB0")
handler.BaudRate = 115200
handler.DataBits = 8
handler.Parity = "N"
handler.StopBits = 1
handler.SlaveId = 1
handler.Timeout = 5 * time.Second

err := handler.Connect()
defer handler.Close()

client := modbus.NewClient(handler)
results, err := client.ReadDiscreteInputs(slaveId, 15, 2)

// Modbus Encapsulated RTU over TCP
handler := modbus.NewEncClientHandler("gateway:20108")
err := handler.Connect()
defer handler.Close()

client := modbus.NewClient(handler)
results, err := client.ReadDiscreteInputs(slaveId, 15, 2)

References

Documentation

Overview

Package modbus provides a client for MODBUS TCP and RTU/ASCII.

Index

Constants

View Source 
const (
	// Bit access
	FuncCodeReadDiscreteInputs = 2
	FuncCodeReadCoils          = 1
	FuncCodeWriteSingleCoil    = 5
	FuncCodeWriteMultipleCoils = 15

	// 16-bit access
	FuncCodeReadInputRegisters         = 4
	FuncCodeReadHoldingRegisters       = 3
	FuncCodeWriteSingleRegister        = 6
	FuncCodeWriteMultipleRegisters     = 16
	FuncCodeReadWriteMultipleRegisters = 23
	FuncCodeMaskWriteRegister          = 22
	FuncCodeReadFIFOQueue              = 24
)
View Source 
const (
	ExceptionCodeIllegalFunction                    = 1
	ExceptionCodeIllegalDataAddress                 = 2
	ExceptionCodeIllegalDataValue                   = 3
	ExceptionCodeServerDeviceFailure                = 4
	ExceptionCodeAcknowledge                        = 5
	ExceptionCodeServerDeviceBusy                   = 6
	ExceptionCodeMemoryParityError                  = 8
	ExceptionCodeGatewayPathUnavailable             = 10
	ExceptionCodeGatewayTargetDeviceFailedToRespond = 11
)
View Source 
const (
	SlaveIdMin = 1
	SlaveIdMax = 255
)

Variables

This section is empty.

Functions

This section is empty.

Types

type ASCIIClientHandler 

type ASCIIClientHandler struct {
	// contains filtered or unexported fields
}

ASCIIClientHandler implements Packager and Transporter interface.

func NewASCIIClientHandler 

func NewASCIIClientHandler(address string) *ASCIIClientHandler

NewASCIIClientHandler allocates and initializes a ASCIIClientHandler.

func (*ASCIIClientHandler) Decode 

func (mb *ASCIIClientHandler) Decode(adu []byte) (pdu *ProtocolDataUnit, err error)

Decode extracts PDU from ASCII frame and verify LRC.

func (*ASCIIClientHandler) Encode 

func (mb *ASCIIClientHandler) Encode(slaveId uint8, pdu *ProtocolDataUnit) (adu []byte, err error)

Encode encodes PDU in a ASCII frame: 

Start           : 1 char
Address         : 2 chars
Function        : 2 chars
Data            : 0 up to 2x252 chars
LRC             : 2 chars
End             : 2 chars

func (*ASCIIClientHandler) Send 

func (mb *ASCIIClientHandler) Send(aduRequest []byte) (aduResponse []byte, err error)

func (*ASCIIClientHandler) Verify 

func (mb *ASCIIClientHandler) Verify(aduRequest []byte, aduResponse []byte) (err error)

Verify verifies response length, frame boundary and slave id.

type Client 

type Client interface {

	// ReadCoils reads from 1 to 2000 contiguous status of coils in a
	// remote device and returns coil status.
	ReadCoils(slaveId uint8, address, quantity uint16) (results []byte, err error)
	// ReadDiscreteInputs reads from 1 to 2000 contiguous status of
	// discrete inputs in a remote device and returns input status.
	ReadDiscreteInputs(slaveId uint8, address, quantity uint16) (results []byte, err error)
	// WriteSingleCoil write a single output to either ON or OFF in a
	// remote device and returns output value.
	WriteSingleCoil(slaveId uint8, address, value uint16) (results []byte, err error)
	// WriteMultipleCoils forces each coil in a sequence of coils to either
	// ON or OFF in a remote device and returns quantity of outputs.
	WriteMultipleCoils(slaveId uint8, address, quantity uint16, value []byte) (results []byte, err error)

	// ReadInputRegisters reads from 1 to 125 contiguous input registers in
	// a remote device and returns input registers.
	ReadInputRegisters(slaveId uint8, address, quantity uint16) (results []byte, err error)
	// ReadHoldingRegisters reads the contents of a contiguous block of
	// holding registers in a remote device and returns register value.
	ReadHoldingRegisters(slaveId uint8, address, quantity uint16) (results []byte, err error)
	// WriteSingleRegister writes a single holding register in a remote
	// device and returns register value.
	WriteSingleRegister(slaveId uint8, address, value uint16) (results []byte, err error)
	// WriteMultipleRegisters writes a block of contiguous registers
	// (1 to 123 registers) in a remote device and returns quantity of
	// registers.
	WriteMultipleRegisters(slaveId uint8, address, quantity uint16, value []byte) (results []byte, err error)
	// ReadWriteMultipleRegisters performs a combination of one read
	// operation and one write operation. It returns read registers value.
	ReadWriteMultipleRegisters(slaveId uint8, readAddress, readQuantity, writeAddress, writeQuantity uint16, value []byte) (results []byte, err error)
	// MaskWriteRegister modify the contents of a specified holding
	// register using a combination of an AND mask, an OR mask, and the
	// register's current contents. The function returns
	// AND-mask and OR-mask.
	MaskWriteRegister(slaveId uint8, address, andMask, orMask uint16) (results []byte, err error)
	//ReadFIFOQueue reads the contents of a First-In-First-Out (FIFO) queue
	// of register in a remote device and returns FIFO value register.
	ReadFIFOQueue(slaveId uint8, address uint16) (results []byte, err error)
}

func ASCIIClient 

func ASCIIClient(address string) Client

ASCIIClient creates ASCII client with default handler and given connect string.

func EncClient 

func EncClient(address string) Client

EncClient creates TCP-RTU client with default handler and given connect string.

func NewClient 

func NewClient(handler ClientHandler) Client

NewClient creates a new modbus client with given backend handler.

func NewClient2 

func NewClient2(packager Packager, transporter Transporter) Client

NewClient2 creates a new modbus client with given backend packager and transporter.

func RTUClient 

func RTUClient(address string) Client

RTUClient creates RTU client with default handler and given connect string.

func TCPClient 

func TCPClient(address string) Client

TCPClient creates TCP client with default handler and given connect string.

type ClientHandler 

type ClientHandler interface {
	Packager
	Transporter
}

ClientHandler is the interface that groups the Packager and Transporter methods.

type EncClientHandler 

type EncClientHandler struct {
	// contains filtered or unexported fields
}

func NewEncClientHandler 

func NewEncClientHandler(address string) *EncClientHandler

func (*EncClientHandler) Close 

func (mb *EncClientHandler) Close() error

Close closes current connection.

func (*EncClientHandler) Connect 

func (mb *EncClientHandler) Connect() error

Connect establishes a new connection to the address in Address. Connect and Close are exported so that multiple requests can be done with one session

func (*EncClientHandler) Decode 

func (mb *EncClientHandler) Decode(adu []byte) (pdu *ProtocolDataUnit, err error)

Decode extracts PDU from RTU frame and verify CRC.

func (*EncClientHandler) Encode 

func (mb *EncClientHandler) Encode(slaveId uint8, pdu *ProtocolDataUnit) (adu []byte, err error)

Encode encodes PDU in a RTU frame: 

Slave Address   : 1 byte
Function        : 1 byte
Data            : 0 up to 252 bytes
CRC             : 2 byte

func (*EncClientHandler) Send 

func (mb *EncClientHandler) Send(aduRequest []byte) (aduResponse []byte, err error)

func (*EncClientHandler) Verify 

func (mb *EncClientHandler) Verify(aduRequest []byte, aduResponse []byte) (err error)

Verify verifies response length and slave id.

type ModbusError 

type ModbusError struct {
	FunctionCode  byte
	ExceptionCode byte
}

ModbusError implements error interface.

func (*ModbusError) Error 

func (e *ModbusError) Error() string

Error converts known modbus exception code to error message.

type Packager 

type Packager interface {
	Encode(slaveId uint8, pdu *ProtocolDataUnit) (adu []byte, err error)
	Decode(adu []byte) (pdu *ProtocolDataUnit, err error)
	Verify(aduRequest []byte, aduResponse []byte) (err error)
}

Packager specifies the communication layer.

type ProtocolDataUnit 

type ProtocolDataUnit struct {
	FunctionCode byte
	Data         []byte
}

ProtocolDataUnit (PDU) is independent of underlying communication layers.

type RTUClientHandler 

type RTUClientHandler struct {
	// contains filtered or unexported fields
}

RTUClientHandler implements Packager and Transporter interface.

func NewRTUClientHandler 

func NewRTUClientHandler(address string) *RTUClientHandler

NewRTUClientHandler allocates and initializes a RTUClientHandler.

func (*RTUClientHandler) Decode 

func (mb *RTUClientHandler) Decode(adu []byte) (pdu *ProtocolDataUnit, err error)

Decode extracts PDU from RTU frame and verify CRC.

func (*RTUClientHandler) Encode 

func (mb *RTUClientHandler) Encode(slaveId uint8, pdu *ProtocolDataUnit) (adu []byte, err error)

Encode encodes PDU in a RTU frame: 

Slave Address   : 1 byte
Function        : 1 byte
Data            : 0 up to 252 bytes
CRC             : 2 byte

func (*RTUClientHandler) Send 

func (mb *RTUClientHandler) Send(aduRequest []byte) (aduResponse []byte, err error)

func (*RTUClientHandler) Verify 

func (mb *RTUClientHandler) Verify(aduRequest []byte, aduResponse []byte) (err error)

Verify verifies response length and slave id.

type TCPClientHandler 

type TCPClientHandler struct {
	// contains filtered or unexported fields
}

TCPClientHandler implements Packager and Transporter interface.

func NewTCPClientHandler 

func NewTCPClientHandler(address string) *TCPClientHandler

NewTCPClientHandler allocates a new TCPClientHandler.

func (*TCPClientHandler) Close 

func (mb *TCPClientHandler) Close() error

Close closes current connection.

func (*TCPClientHandler) Connect 

func (mb *TCPClientHandler) Connect() error

Connect establishes a new connection to the address in Address. Connect and Close are exported so that multiple requests can be done with one session

func (*TCPClientHandler) Decode 

func (mb *TCPClientHandler) Decode(adu []byte) (pdu *ProtocolDataUnit, err error)

Decode extracts PDU from TCP frame: 

Transaction identifier: 2 bytes
Protocol identifier: 2 bytes
Length: 2 bytes
Unit identifier: 1 byte

func (*TCPClientHandler) Encode 

func (mb *TCPClientHandler) Encode(slaveId uint8, pdu *ProtocolDataUnit) (adu []byte, err error)

Encode adds modbus application protocol header: 

Transaction identifier: 2 bytes
Protocol identifier: 2 bytes
Length: 2 bytes
Unit identifier: 1 byte
Function code: 1 byte
Data: n bytes

func (*TCPClientHandler) Send 

func (mb *TCPClientHandler) Send(aduRequest []byte) (aduResponse []byte, err error)

Send sends data to server and ensures response length is greater than header length.

func (*TCPClientHandler) Verify 

func (mb *TCPClientHandler) Verify(aduRequest []byte, aduResponse []byte) (err error)

Verify confirms transaction, protocol and unit id.

type Transporter 

type Transporter interface {
	Send(aduRequest []byte) (aduResponse []byte, err error)
}

Transporter specifies the transport layer.

Source Files

View all Source files

Directories

Path Synopsis
commw32
Port of commw32.c To generate go types: go tool cgo commw32.go
 Port of commw32.c To generate go types: go tool cgo commw32.go

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