PL::ModbusServer class

class ModbusServer : public PL::ModbusBase, public PL::Server 

Modbus server class.

Public Functions

ModbusServer(std::shared_ptr<Stream> stream, ModbusProtocol protocol, uint8_t stationAddress, std::shared_ptr<Buffer> buffer)

Creates a stream Modbus server with shared transaction buffer.

Parameters:

stream – stream
protocol – Modbus protocol
stationAddress – station address
buffer – transaction buffer

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

Creates an stream Modbus server and allocates transaction buffer.

Parameters:

stream – stream
protocol – Modbus protocol
stationAddress – station address
bufferSize – transaction buffer size

ModbusServer(uint16_t port, std::shared_ptr<Buffer> buffer)

Creates a network Modbus server with shared transaction buffer.

Parameters:

port – network port
buffer – transaction buffer

ModbusServer(uint16_t port, size_t bufferSize = defaultBufferSize)

Creates a network Modbus server and allocates transaction buffer.

Parameters:

port – network port
bufferSize – transaction buffer size

~ModbusServer(): Note

Every derived class must call StopTask as the first statement of its own destructor so that the base server task does not call HandleRequest on a partially destroyed object.

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

virtual esp_err_t Enable() override

Enables the server.

Returns:: error code

virtual esp_err_t Disable() override

Disables the server.

Returns:: error code

virtual esp_err_t SetProtocol(ModbusProtocol protocol) override: Note

Returns an error if called from HandleRequest, since changing the protocol mid-transaction would desynchronize the data buffer written by HandleRequest from the one WriteFrame sends.

void AddMemoryArea(std::shared_ptr<ModbusMemoryArea> memoryArea)

Adds a Modbus memory area to the server.

Parameters:: memoryArea – memory area
Returns:: error code

void AddMemoryArea(ModbusMemoryType type, uint16_t address, std::shared_ptr<Buffer> buffer)

Adds buffer as a Modbus memory area to the server.

Parameters:

type – memory area type
address – memory area address
buffer – buffer

virtual bool IsEnabled() override

Checks if the server is enabled.

Returns:: true if the server is enabled

uint8_t GetStationAddress()

Gets the Modbus station address.

Returns:: station address

esp_err_t SetStationAddress(uint8_t stationAddress)

Sets the Modbus station address.

Parameters:: stationAddress – station address
Returns:: error code

esp_err_t SetTaskParameters(const TaskParameters &taskParameters)

Sets the server task parameters.

Parameters:: taskParameters – task parameters
Returns:: error code

std::weak_ptr<Server> GetBaseServer()

Gets the base server (StreamServer or TcpServer)

Returns:: base server

ModbusProtocol GetProtocol()

Gets Modbus protocol.

Returns:: protocol

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 GetWriteTimeout()

Gets the write operation timeout.

Returns:: timeout in FreeRTOS ticks

esp_err_t SetWriteTimeout(TickType_t timeout)

Sets the write 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

std::string GetName()

Gets the server name.

Returns:: name

void SetName(const std::string &name)

Sets the server name.

Parameters:: name – name

Public Members

Event<Server> enabledEvent: server enabled event

Event<Server> disabledEvent: server disabled event

Public Static Attributes

static constexpr const char *defaultName = "Modbus Server": Default server name.

static constexpr TickType_t defaultReadTimeout = 3: Default read operation timeout in FreeRTOS ticks.

static constexpr TickType_t defaultWriteTimeout = 300 / portTICK_PERIOD_MS: Default write operation timeout in FreeRTOS ticks.

static constexpr size_t defaultBufferSize = 260: Default transaction buffer size.

Note

Sized for the largest RTU/TCP transaction.

static constexpr ModbusProtocol defaultNetworkProtocol = ModbusProtocol::tcp : Default protocol for network interface.

static constexpr uint8_t defaultNetworkStationAddress = 255: Default station address for network interface.

static constexpr uint16_t maxNumberOfModbusBitsToRead = 2000: Maximum number of coils or discrete inputs that can be read in one request.

static constexpr uint16_t maxNumberOfModbusBitsToWrite = 1968: Maximum number of coils that can be written in one request.

static constexpr uint16_t maxNumberOfModbusRegistersToRead = 125: Maximum number of holding or input registers that can be read in one request.

static constexpr uint16_t maxNumberOfModbusRegistersToWrite = 123: Maximum number of holding registers that can be written in one request.

Protected Functions

esp_err_t StopTask()

Stops the base server task and waits for it to exit.

Note

Must be called as the first statement of the destructor of every derived class so that the base server task does not call HandleRequest on a partially destroyed object. Aborts if called from the HandleRequest, since it cannot wait for its own task to exit.

Returns:: error code

virtual esp_err_t StreamRead(Stream &stream, void *dest, size_t size) override

Reads data from the stream (overriden in ModbusServer to read one byte at a time)

Parameters:

stream – stream to read from
dest – destination (can be NULL)
size – number of bytes to read

Returns:

error code

virtual esp_err_t StreamRead(Stream &stream, Buffer &dest, size_t offset, size_t size) override

Reads data from the stream into the buffer (overriden in ModbusServer to read one byte at a time)

Parameters:

stream – stream to read from
dest – destination buffer
offset – destination buffer offset
size – number of bytes to read

Returns:

error code

virtual esp_err_t StreamReadUntil(Stream &stream, char termChar) override

Reads the data from the stream up to the specified termination character (overriden in ModbusServer to read one byte at a time)

Parameters:

stream – stream to read from
termChar – termination character

Returns:

error code

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

virtual esp_err_t HandleRequest(Stream &stream, uint8_t stationAddress, ModbusFunctionCode functionCode, size_t dataSize, uint16_t transactionId)

Handles the Modbus client request.

Parameters:

stream – client stream
stationAddress – request station address
functionCode – request function code
dataSize – request data size
transactionId – request transaction ID (for Modbus TCP protocol)

Returns:

error code

esp_err_t WriteExceptionFrame(Stream &stream, uint8_t stationAddress, ModbusFunctionCode functionCode, ModbusException exception, uint16_t transactionId)

Writes the Modbus exception frame.

Parameters:

stream – client stream
stationAddress – frame station address
functionCode – frame function code
exception – Modbus exception
transactionId – frame transaction ID (for Modbus TCP protocol)

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