Member Function Documentation

QModbusDevice::QModbusDevice(QObject *parent = nullptr)

Constructs a Modbus device with the specified parent.

[signal] void QModbusDevice::errorOccurred(QModbusDevice::Error error)

This signal is emitted when an error of the type, error, occurs.

[signal] void QModbusDevice::stateChanged(QModbusDevice::State state)

This signal is emitted every time the state of the device changes. The new state is represented by state.

See also setState() and state().

[virtual] QModbusDevice::~QModbusDevice()

Destroys the QModbusDevice instance

[pure virtual protected] void QModbusDevice::close()

This function is responsible for closing the Modbus connection. The implementation must ensure that the instance's state() is set to QModbusDevice::UnconnectedState.

See also disconnectDevice().

bool QModbusDevice::connectDevice()

Connects the device to the Modbus network. Returns true if the connection process was successfully initiated; otherwise false. Final connection success confirmation requires the state() changing to QModbusDevice::ConnectedState.

This function calls open() as part of its implementation.

See also open().

QVariant QModbusDevice::connectionParameter(int parameter) const

Returns the value associated with the given connection parameter. The returned value can be empty.

By default the QModbusDevice is initialized with some common values. The serial port settings are even parity, a baud rate of 19200 bits per second, eight data bits and one stop bit. The network settings for the host address is set to local host and port to 502.

Note: For a serial connection to succeed, the SerialPortNameParameter needs to be set to a valid communication port. The information about valid serial ports can be obtained from QSerialPortInfo.

Note: If the device is already connected, the settings are taken into account after reconnecting the device.

See also setConnectionParameter() and ConnectionParameter.

QIODevice *QModbusDevice::device() const

Returns the underlying QIODevice used for ModBus communication or nullptr if the device was not yet fully initialized.

Note: Do not store a pointer to the underlying device, because it can be invalidated at any point in time.

This function was introduced in Qt 5.14.

void QModbusDevice::disconnectDevice()

Disconnects the device.

This function calls close() as part of its implementation.

QModbusDevice::Error QModbusDevice::error() const

Returns the error state of the device.

See also setError() and QModbusDevice::Error.

QString QModbusDevice::errorString() const

Returns descriptive error text for the device error.

See also QModbusDevice::Error.

[pure virtual protected] bool QModbusDevice::open()

This function is called by connectDevice(). Subclasses must provide an implementation that returns true on successful Modbus connection or connection initiation; otherwise returns false.

The implementation must ensure that the instance's state() is set to QModbusDevice::ConnectingState or QModbusDevice::ConnectedState upon success; otherwise QModbusDevice::UnconnectedState. Typically, QModbusDevice::ConnectingState is used when the connection process reports back asynchronously and QModbusDevice::ConnectedState in case of synchronous connect behavior.

See also connectDevice().

void QModbusDevice::setConnectionParameter(int parameter, const QVariant &value)

Sets the value of parameter to value. If the parameter already exists, the previous value is overwritten. A active or running connection is not affected by such parameter changes.

See also ConnectionParameter and connectionParameter().

[protected] void QModbusDevice::setError(const QString &errorText, QModbusDevice::Error error)

Sets the error state of the device. ModBus device implementations must use this function in case of an error to set the error type and a descriptive errorText.

See also error() and QModbusDevice::Error.

[protected] void QModbusDevice::setState(QModbusDevice::State newState)

Sets the state of the device to newState. Modbus device implementations must use this function to update the device state.

See also state().

QModbusDevice::State QModbusDevice::state() const

Returns the current state of the device.

See also setState() and stateChanged().