PL::ModbusClient class

class ModbusClient : public PL::ModbusBase

Modbus client class.

Public Functions

ModbusClient(std::shared_ptr<Stream> stream, ModbusProtocol protocol, uint8_t stationAddress, size_t bufferSize = defaultBufferSize)

Creates a stream Modbus client.

Parameters:

  • stream – stream

  • protocol – Modbus protocol

  • stationAddress – station address

  • bufferSize – transaction buffer size

ModbusClient(IpV4Address address, uint16_t port, size_t bufferSize = defaultBufferSize)

Creates a network Modbus client with IPv4 remote address.

Parameters:

  • address – remote IPv4 address

  • port – remote port

  • bufferSize – transaction buffer size

ModbusClient(IpV6Address address, uint16_t port, size_t bufferSize = defaultBufferSize)

Creates a network Modbus client with IPv6 remote address.

Parameters:

  • address – remote IPv6 address

  • port – remote port

  • bufferSize – transaction buffer size

ModbusClient(std::shared_ptr<TcpClient> tcpClient, size_t bufferSize = defaultBufferSize)

Creates a network Modbus client using shared TCP client.

Parameters:

  • tcpClient – TCP client

  • bufferSize – transaction buffer size

virtual esp_err_t Lock(TickType_t timeout = portMAX_DELAY) override

Locks the object.

Parameters:

timeout – timeout in FreeRTOS ticks

Returns:

error code

virtual esp_err_t Unlock() override

Unlocks the object.

Returns:

error code

esp_err_t Command(ModbusFunctionCode functionCode, const void *requestData, size_t requestDataSize, void *responseData, size_t maxResponseDataSize, size_t *responseDataSize, ModbusException *exception)

Sends a Modbus request and returns response data.

Parameters:

  • functionCode – request function code

  • requestData – request data pointer

  • requestDataSize – request data size

  • responseData – response data pointer

  • maxResponseDataSize – maximum response data size

  • responseDataSize – response data size

  • exception – Modbus exception

Returns:

error code

esp_err_t ReadCoils(uint16_t address, uint16_t numberOfItems, void *responseData, ModbusException *exception)

Reads coils.

Parameters:

  • address – first coil address

  • numberOfItems – number of coils

  • responseData – coil values (8 values per byte)

  • exception – Modbus exception

Returns:

error code

esp_err_t ReadDiscreteInputs(uint16_t address, uint16_t numberOfItems, void *responseData, ModbusException *exception)

Reads discrete inputs.

Parameters:

  • address – first discrete input address

  • numberOfItems – number of discrete inputs

  • responseData – discrete input values (8 values per byte)

  • exception – Modbus exception

Returns:

error code

esp_err_t ReadHoldingRegisters(uint16_t address, uint16_t numberOfItems, void *responseData, ModbusException *exception)

Reads holding registers.

Parameters:

  • address – first holding register address

  • numberOfItems – number of holding registers

  • responseData – holding register values

  • exception – Modbus exception

Returns:

error code

esp_err_t ReadInputRegisters(uint16_t address, uint16_t numberOfItems, void *responseData, ModbusException *exception)

Reads input registers.

Parameters:

  • address – first input register address

  • numberOfItems – number of input registers

  • responseData – input register values

  • exception – Modbus exception

Returns:

error code

esp_err_t WriteSingleCoil(uint16_t address, bool value, ModbusException *exception)

Writes single coil.

Parameters:

  • address – coil address

  • value – coil value

  • exception – Modbus exception

Returns:

error code

esp_err_t WriteSingleHoldingRegister(uint16_t address, uint16_t value, ModbusException *exception)

Writes single holding register.

Parameters:

  • address – holding register address

  • value – holding register value

  • exception – Modbus exception

Returns:

error code

esp_err_t WriteMultipleCoils(uint16_t address, uint16_t numberOfItems, const void *requestData, ModbusException *exception)

Writes multiple coils.

Parameters:

  • address – first coil address

  • numberOfItems – number of coils

  • requestData – coil values (8 values per byte)

  • exception – Modbus exception

Returns:

error code

esp_err_t WriteMultipleHoldingRegisters(uint16_t address, uint16_t numberOfItems, const void *requestData, ModbusException *exception)

Writes multiple holding registers.

Parameters:

  • address – first holding register address

  • numberOfItems – number of holding registers

  • requestData – holding register values

  • exception – Modbus exception

Returns:

error code

uint8_t GetStationAddress()

Gets the Modbus station address.

Returns:

station address

esp_err_t SetStationAddress(uint8_t address)

Sets the Modbus station address.

Parameters:

address – station address

Returns:

error code

ModbusProtocol GetProtocol()

Gets Modbus protocol.

Returns:

protocol

virtual esp_err_t SetProtocol(ModbusProtocol protocol)

Sets Modbus protocol.

Parameters:

protocol – protocol

Returns:

error code

TickType_t GetReadTimeout()

Gets the read operation timeout.

Returns:

timeout in FreeRTOS ticks

esp_err_t SetReadTimeout(TickType_t timeout)

Sets the read operation timeout.

Parameters:

timeout – timeout in FreeRTOS ticks

Returns:

error code

TickType_t GetDelayAfterRead()

Gets the delay between the end of the read operation and unlocking the stream.

Returns:

delay in FreeRTOS ticks

esp_err_t SetDelayAfterRead(TickType_t delay)

Sets the delay between the end of the read operation and unlocking the stream.

Parameters:

delay – delay in FreeRTOS ticks

Returns:

error code

Public Static Attributes

static const TickType_t defaultReadTimeout = 300 / portTICK_PERIOD_MS

Default read operation timeout in FreeRTOS ticks.

static const size_t defaultBufferSize = 260

Default transaction buffer size.

static const ModbusProtocol defaultNetworkProtocol = ModbusProtocol::tcp

Default protocol for network interface.

static const uint8_t defaultNetworkStationAddress = 255

Default station address for network interface.

static const uint16_t maxNumberOfModbusBitsToRead = 2000

Maximum number of coils or discrete inputs that can be read in one request.

static const uint16_t maxNumberOfModbusBitsToWrite = 1968

Maximum number of coils that can be written in one request.

static const uint16_t maxNumberOfModbusRegistersToRead = 125

Maximum number of holding or input registers that can be read in one request.

static const uint16_t maxNumberOfModbusRegistersToWrite = 123

Maximum number of holding registers that can be written in one request.

Protected Functions

virtual esp_err_t ReadRtuData(Stream &stream, ModbusFunctionCode functionCode, size_t &dataSize) override

Reads the data for the specified function code (for Modbus RTU protocol).

Parameters:

  • stream – stream to read from

  • functionCode – frame function code

  • dataSize – frame data size

Returns:

error code

esp_err_t ReadFrame(Stream &stream, uint8_t &stationAddress, ModbusFunctionCode &functionCode, size_t &dataSize, uint16_t &transactionId)

Reads the Modbus frame.

Parameters:

  • stream – stream to read from

  • stationAddress – frame station address

  • functionCode – frame function code

  • dataSize – frame data size

  • transactionId – frame transaction ID (for Modbus TCP protocol)

Returns:

error code

esp_err_t WriteFrame(Stream &stream, uint8_t stationAddress, ModbusFunctionCode functionCode, size_t dataSize, uint16_t transactionId)

Writes the Modbus frame.

Parameters:

  • stream – stream to write to

  • stationAddress – frame station address

  • functionCode – frame function code

  • dataSize – frame data size

  • transactionId – frame transaction ID (for Modbus TCP protocol)

Returns:

error code

Buffer &GetDataBuffer()

Gets the data part of the transaction buffer with offset and size based on the Modbus protocol.

Returns:

data buffer