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Arduino Modbus Library

Modbus Client

client.coilRead()

Description

Perform a "Read Coils" operation for the specified address for a single coil.

Syntax

int coilRead(int address);
int coilRead(int id, int address);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation

Returns

coil value on success, -1 on failure.

client.discreteInputRead()

Description

Perform a "Read Discrete Inputs" operation for the specified address for a single discrete input.

Syntax

int discreteInputRead(int address);
int discreteInputRead(int id, int address);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation

Returns

discrete input value on success, -1 on failure.

client.holdingRegisterRead()

Description

Perform a "Read Holding Registers" operation for a single holding register.

Syntax

long holdingRegisterRead(int address);
long holdingRegisterRead(int id, int address);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address start address to use for operation
  • holding register value on success, -1 on failure.

client.inputRegisterRead()

Description

Perform a "Read Input Registers" operation for a single input register.

Syntax

long inputRegisterRead(int address);
long inputRegisterRead(int id, int address);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation

Returns

input register value on success, -1 on failure.

client.coilWrite()

Description

Perform a "Write Single Coil" operation for the specified address and value.

Syntax

int coilWrite(int address, uint8_t value);
int coilWrite(int id, int address, uint8_t value);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation
  • value coi -l value to write

Returns

1 on success, 0 on failure.

client.holdingRegisterWrite()

Description

Perform a "Write Single Holding Register" operation for the specified address and value.

Syntax

int holdingRegisterWrite(int address, uint16_t value);
int holdingRegisterWrite(int id, int address, uint16_t value);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation
  • value - holding register value to write

Returns

1 on success, 0 on failure.

client.registerMaskWrite()

Description

Perform a "Mask Write Registers" operation for the specified address, AND mask and OR mask.

Syntax

int registerMaskWrite(int address, uint16_t andMask, uint16_t orMask);
int registerMaskWrite(int id, int address, uint16_t andMask, uint16_t orMask);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation
  • andMask - AND mask to use for operation
  • orMask - OR mask to use for operation

Returns

1 on success, 0 on failure.

client.beginTransmission()

Description

Begin the process of a writing multiple coils or holding registers. Use write(value) to set the values you want to send, and endTransmission() to send request on the wire.

Syntax

int beginTransmission(int type, int address, int nb);
int beginTransmission(int id, int type, int address, int nb);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • type - type of write to perform, either COILS or HOLDING_REGISTERS
  • address start address to use for operation
  • nb - number of values to write

Returns

1 on success, 0 on failure

client.write()

Description

Set the values of a write operation started by beginTransmission(...).

Syntax

int write(unsigned int value);

Parameters

  • value - value to write

Returns

1 on success, 0 on failure

client.endTransmission()

Description

End the process of a writing multiple coils or holding registers.

Syntax

int endTransmission();

Parameters

none

Returns

1 on success, 0 on failure

client.requestFrom()

Description

Read multiple coils, discrete inputs, holding registers, or input register values. Use available() and read() to process the read values.

Syntax

int requestFrom(int type, int address, int nb);
int requestFrom(int id, int type, int address,int nb);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • type - type of read to perform, either COILS, DISCRETE_INPUTS, HOLDING_REGISTERS, or INPUT_REGISTERS
  • address start address to use for operation
  • nb - number of values to read

Returns

0 on failure, number of values read on success

client.available()

Description

Query the number of values available to read after calling requestFrom(...)

Syntax

int available();

Parameters

none

Returns

number of values available for reading use read()

client.read()

Description

Read a value after calling requestFrom(...)

Syntax

long read();

Parameters

None

Returns

-1 on failure, value on success

client.lastError()

Description

Read the last error reason as a string

Syntax

const char* lastError();

Parameters

none

Returns

Last error reason as a C string

client.end()

Description

Stop the client and clean up

Syntax

void end();

Parameters

None

Returns

nothing

ModbusRTUClient Class

modbusRTUClient.begin()

Description

Start the Modbus RTU client with the specified parameters.

Syntax

ModbusRTUClient.begin(baudrate);
ModbusRTUClient.begin(baudrate, config);

Parameters

  • baudrate - Baud rate to use for serial
  • config - Config to use for serial (see Serial.begin(...) for more info.) defaults to SERIAL_8N1 if not provided

Returns

1 on success, 0 on failure

ModbusTCPClient Class

ModbusTCPClient()

Description

Creates a Modbus TCP client using the provided Client for the transport.

Syntax

ModbusTCPClient(client);

Parameters

  • Client - to use for the transport

modbusTCPClient.begin()

Description

Start the Modbus TCP client with the specified parameters.

Syntax

modbusTCPClient.begin(ip, port);

Parameters

  • ip - the IP Address the client will connect to
  • port - port to the client will connect to

Returns

1 on success, 0 on failure

modbusTCPClient.connected()

Description

Returns the connection status.

Syntax

modbusTCPClient.connected();

Parameters

None

Returns

Returns true if the client is connected, false if not.

modbusTCPClient.stop()

Description

Disconnect from the server.

Syntax

modbusTCPClient.stop();

Parameters

None

Returns

Nothing

ModbusServer Class

modbusServer.configureCoils()

Description

Configure the servers coils.

Syntax

int configureCoils(int startAddress, int nb);

Parameters

  • startAddress - start address of coils
  • nb - number of coils to configure

Returns

0 on success, 1 on failure

modbusServer.configureDiscreteInputs()

Description

Configure the servers discrete inputs.

Syntax

int configureDiscreteInputs(int startAddress, int nb);

Parameters

  • startAddress - start address of discrete inputs
  • nb - number of discrete inputs to configure

Returns

0 on success, 1 on failure

modbusServer.configureHoldingRegisters()

Description

Configure the servers holding registers.

Syntax

int configureHoldingRegisters(int startAddress, int nb);

Parameters

  • startAddress - start address of holding registers
  • nb - number of holding registers to configure

Returns

0 on success, 1 on failure

modbusServer.configureInputRegisters()

Description

Configure the servers input registers.

Syntax

int configureInputRegisters(int startAddress, int nb);

Parameters

  • startAddress - start address of input registers
  • nb - number of input registers to configure

Returns

0 on success, 1 on failure

modbusServer.coilRead()

Description

Perform a "Read Coils" operation for the specified address for a single coil.

Syntax

int coilRead(int address);
int coilRead(int id, int address);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation

Returns

coil value on success, -1 on failure.

modbusServer.discreteInputRead()

Description

Perform a "Read Discrete Inputs" operation for the specified address for a single discrete input.

Syntax

int discreteInputRead(int address);
int discreteInputRead(int id, int address);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation

Returns

discrete input value on success, -1 on failure.

modbusServer.holdingRegisterRead()

Description

Perform a "Read Holding Registers" operation for a single holding register.

Syntax

long holdingRegisterRead(int address);
long holdingRegisterRead(int id, int address);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address start address to use for operation
  • holding register value on success, -1 on failure.

modbusServer.inputRegisterRead()

Description

Perform a "Read Input Registers" operation for a single input register.

Syntax

long inputRegisterRead(int address);
long inputRegisterRead(int id, int address);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation

Returns

input register value on success, -1 on failure.

modbusServer.coilWrite()

Description

Perform a "Write Single Coil" operation for the specified address and value.

Syntax

int coilWrite(int address, uint8_t value);
int coilWrite(int id, int address, uint8_t value);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation
  • value coi -l value to write

Returns

1 on success, 0 on failure.

modbusServer.holdingRegisterWrite()

Description

Perform a "Write Single Holding Register" operation for the specified address and value.

Syntax

int holdingRegisterWrite(int address, uint16_t value);
int holdingRegisterWrite(int id, int address, uint16_t value);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation
  • value - holding register value to write

Returns

1 on success, 0 on failure.

modbusServer.registerMaskWrite()

Description

Perform a "Mask Write Registers" operation for the specified address, AND mask and OR mask.

Syntax

int registerMaskWrite(int address, uint16_t andMask, uint16_t orMask);
int registerMaskWrite(int id, int address, uint16_t andMask, uint16_t orMask);

Parameters

  • id (slave) - id of target, defaults to 0x00 if not specified
  • address address to use for operation
  • andMask - AND mask to use for operation
  • orMask - OR mask to use for operation

Returns

1 on success, 0 on failure.

modbusServer.discreteInputWrite()

Description

Write the value of the server's Discrete Input for the specified address and value.

Syntax

int discreteInputWrite(int address, uint8_t value);

Parameters

  • address address to use for operation
  • value - discrete input value to write

Returns

1 on success, 0 on failure.

modbusServer.writeDiscreteInputs()

Description

Write values to the server's Discrete Inputs for the specified address and values.

Syntax

int writeDiscreteInputs(int address, uint8_t values[], int nb);

Parameters

  • address address to use for operation
  • values - array of discrete inputs values to write
  • nb - number of discrete inputs to write

Returns

1 on success, 0 on failure.

modbusServer.inputRegisterWrite()

Description

Write the value of the server's Input Register for the specified address and value.

Syntax

int inputRegisterWrite(int address, uint16_t value);

Parameters

  • address address to use for operation
  • value - input register value to write

Returns

1 on success, 0 on failure.

modbusServer.writeInputRegisters()

Description

Write values to the server's Input Registers for the specified address and values.

Syntax

int writeInputRegisters(int address, uint16_t values[], int nb);

Parameters

  • address address to use for operation
  • values - array of input registers values to write
  • nb - number of input registers to write

Returns

1 on success, 0 on failure.

modbusServer.poll()

Description

Poll for requests

Syntax

virtual void poll() = 0;

Parameters

None

Returns

nothing

modbusServer.end()

Description

Stop the server

Syntax

void end();

Parameters

None

Return

nothing

ModbusRTUServer Class

modbusRTUServer.begin()

Description

Start the Modbus RTU server with the specified parameters.

Syntax

ModbusRTUServer.begin(id, baudrate);
ModbusRTUServer.begin(id, baudrate, config);

Parameters

  • id - (slave) id of the server baudrate - Baud rate to use for serial
  • config - Config to use for serial (see Serial.begin(...) for more info.) defaults to SERIAL_8N1 if not provided

Returns

1 on success, 0 on failure

ModbusTCPServer

ModbusTCPServer()

Description

Creates a Modbus TCP server.

Syntax

ModbusTCPServer();

Parameters

None

modbusTCPServer.begin()

Description

Start the Modbus TCP server.

Syntax

modbusTCPserver.begin();
modbusTCPserver.begin(id);

Parameters

  • id - the (slave) id of the server, defaults to 0xff (TCP);

Returns

1 on success, 0 on failure

modbusTCPServer.accept()

Description

Accept a client connection.

Syntax

modbusTCPserver.accept(client);

Parameters

  • client - the Client to accept a connection from;

Returns

Nothing