Modbus Master example

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#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "settingsdialog.h"
#include "writeregistermodel.h"

#include <QModbusTcpClient>
#include <QModbusRtuSerialMaster>
#include <QStandardItemModel>
#include <QStatusBar>
#include <QUrl>

enum ModbusConnection {
    Serial,
    Tcp
};

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , lastRequest(nullptr)
    , modbusDevice(nullptr)
{
    ui->setupUi(this);

    m_settingsDialog = new SettingsDialog(this);

    initActions();

    writeModel = new WriteRegisterModel(this);
    writeModel->setStartAddress(ui->writeAddress->value());
    writeModel->setNumberOfValues(ui->writeSize->currentText());

    ui->writeValueTable->setModel(writeModel);
    ui->writeValueTable->hideColumn(2);
    connect(writeModel, &WriteRegisterModel::updateViewport, ui->writeValueTable->viewport(),
        static_cast<void (QWidget::*)()>(&QWidget::update));

    ui->writeTable->addItem(tr("Coils"), QModbusDataUnit::Coils);
    ui->writeTable->addItem(tr("Discrete Inputs"), QModbusDataUnit::DiscreteInputs);
    ui->writeTable->addItem(tr("Input Registers"), QModbusDataUnit::InputRegisters);
    ui->writeTable->addItem(tr("Holding Registers"), QModbusDataUnit::HoldingRegisters);

    ui->connectType->setCurrentIndex(0);
    on_connectType_currentIndexChanged(0);

    auto model = new QStandardItemModel(10, 1, this);
    for (int i = 0; i < 10; ++i)
        model->setItem(i, new QStandardItem(QStringLiteral("%1").arg(i + 1)));
    ui->writeSize->setModel(model);
    ui->writeSize->setCurrentText("10");
    connect(ui->writeSize,&QComboBox::currentTextChanged, writeModel,
        &WriteRegisterModel::setNumberOfValues);

    auto valueChanged = static_cast<void (QSpinBox::*)(int)> (&QSpinBox::valueChanged);
    connect(ui->writeAddress, valueChanged, writeModel, &WriteRegisterModel::setStartAddress);
    connect(ui->writeAddress, valueChanged, this, [this, model](int i) {
        int lastPossibleIndex = 0;
        const int currentIndex = ui->writeSize->currentIndex();
        for (int ii = 0; ii < 10; ++ii) {
            if (ii < (10 - i)) {
                lastPossibleIndex = ii;
                model->item(ii)->setEnabled(true);
            } else {
                model->item(ii)->setEnabled(false);
            }
        }
        if (currentIndex > lastPossibleIndex)
            ui->writeSize->setCurrentIndex(lastPossibleIndex);
    });
}

MainWindow::~MainWindow()
{
    if (modbusDevice)
        modbusDevice->disconnectDevice();
    delete modbusDevice;

    delete ui;
}

void MainWindow::initActions()
{
    ui->actionConnect->setEnabled(true);
    ui->actionDisconnect->setEnabled(false);
    ui->actionExit->setEnabled(true);
    ui->actionOptions->setEnabled(true);

    connect(ui->actionConnect, &QAction::triggered,
            this, &MainWindow::on_connectButton_clicked);
    connect(ui->actionDisconnect, &QAction::triggered,
            this, &MainWindow::on_connectButton_clicked);

    connect(ui->actionExit, &QAction::triggered, this, &QMainWindow::close);
    connect(ui->actionOptions, &QAction::triggered, m_settingsDialog, &QDialog::show);
}

void MainWindow::on_connectType_currentIndexChanged(int index)
{
    if (modbusDevice) {
        modbusDevice->disconnectDevice();
        delete modbusDevice;
        modbusDevice = nullptr;
    }

    auto type = static_cast<ModbusConnection> (index);
    if (type == Serial) {
        modbusDevice = new QModbusRtuSerialMaster(this);
    } else if (type == Tcp) {
        modbusDevice = new QModbusTcpClient(this);
        if (ui->portEdit->text().isEmpty())
            ui->portEdit->setText(QLatin1Literal("127.0.0.1:502"));
    }

    connect(modbusDevice, &QModbusClient::errorOccurred, [this](QModbusDevice::Error) {
        statusBar()->showMessage(modbusDevice->errorString(), 5000);
    });

    if (!modbusDevice) {
        ui->connectButton->setDisabled(true);
        if (type == Serial)
            statusBar()->showMessage(tr("Could not create Modbus master."), 5000);
        else
            statusBar()->showMessage(tr("Could not create Modbus client."), 5000);
    } else {
        connect(modbusDevice, &QModbusClient::stateChanged,
                this, &MainWindow::onStateChanged);
    }
}

void MainWindow::on_connectButton_clicked()
{
    if (!modbusDevice)
        return;

    statusBar()->clearMessage();
    if (modbusDevice->state() != QModbusDevice::ConnectedState) {
        if (static_cast<ModbusConnection> (ui->connectType->currentIndex()) == Serial) {
            modbusDevice->setConnectionParameter(QModbusDevice::SerialPortNameParameter,
                ui->portEdit->text());
            modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,
                m_settingsDialog->settings().parity);
            modbusDevice->setConnectionParameter(QModbusDevice::SerialBaudRateParameter,
                m_settingsDialog->settings().baud);
            modbusDevice->setConnectionParameter(QModbusDevice::SerialDataBitsParameter,
                m_settingsDialog->settings().dataBits);
            modbusDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,
                m_settingsDialog->settings().stopBits);
        } else {
            const QUrl url = QUrl::fromUserInput(ui->portEdit->text());
            modbusDevice->setConnectionParameter(QModbusDevice::NetworkPortParameter, url.port());
            modbusDevice->setConnectionParameter(QModbusDevice::NetworkAddressParameter, url.host());
        }
        modbusDevice->setTimeout(m_settingsDialog->settings().responseTime);
        modbusDevice->setNumberOfRetries(m_settingsDialog->settings().numberOfRetries);
        if (!modbusDevice->connectDevice()) {
            statusBar()->showMessage(tr("Connect failed: ") + modbusDevice->errorString(), 5000);
        } else {
            ui->actionConnect->setEnabled(false);
            ui->actionDisconnect->setEnabled(true);
        }
    } else {
        modbusDevice->disconnectDevice();
        ui->actionConnect->setEnabled(true);
        ui->actionDisconnect->setEnabled(false);
    }
}

void MainWindow::onStateChanged(int state)
{
    bool connected = (state != QModbusDevice::UnconnectedState);
    ui->actionConnect->setEnabled(!connected);
    ui->actionDisconnect->setEnabled(connected);

    if (state == QModbusDevice::UnconnectedState)
        ui->connectButton->setText(tr("Connect"));
    else if (state == QModbusDevice::ConnectedState)
        ui->connectButton->setText(tr("Disconnect"));
}

void MainWindow::on_readButton_clicked()
{
    if (!modbusDevice)
        return;
    ui->readValue->clear();
    statusBar()->clearMessage();

    if (auto *reply = modbusDevice->sendReadRequest(readRequest(), ui->serverEdit->value())) {
        if (!reply->isFinished())
            connect(reply, &QModbusReply::finished, this, &MainWindow::readReady);
        else
            delete reply; // broadcast replies return immediately
    } else {
        statusBar()->showMessage(tr("Read error: ") + modbusDevice->errorString(), 5000);
    }
}

void MainWindow::readReady()
{
    auto reply = qobject_cast<QModbusReply *>(sender());
    if (!reply)
        return;

    if (reply->error() == QModbusDevice::NoError) {
        const QModbusDataUnit unit = reply->result();
        for (uint i = 0; i < unit.valueCount(); i++) {
            const QString entry = tr("Address: %1, Value: %2").arg(unit.startAddress() + i)
                                     .arg(QString::number(unit.value(i),
                                          unit.registerType() <= QModbusDataUnit::Coils ? 10 : 16));
            ui->readValue->addItem(entry);
        }
    } else if (reply->error() == QModbusDevice::ProtocolError) {
        statusBar()->showMessage(tr("Read response error: %1 (Mobus exception: 0x%2)").
                                    arg(reply->errorString()).
                                    arg(reply->rawResult().exceptionCode(), -1, 16), 5000);
    } else {
        statusBar()->showMessage(tr("Read response error: %1 (code: 0x%2)").
                                    arg(reply->errorString()).
                                    arg(reply->error(), -1, 16), 5000);
    }

    reply->deleteLater();
}

void MainWindow::on_writeButton_clicked()
{
    if (!modbusDevice)
        return;
    statusBar()->clearMessage();

    QModbusDataUnit writeUnit = writeRequest();
    QModbusDataUnit::RegisterType table = writeUnit.registerType();
    for (uint i = 0; i < writeUnit.valueCount(); i++) {
        if (table == QModbusDataUnit::Coils)
            writeUnit.setValue(i, writeModel->m_coils[i + writeUnit.startAddress()]);
        else
            writeUnit.setValue(i, writeModel->m_holdingRegisters[i + writeUnit.startAddress()]);
    }

    if (auto *reply = modbusDevice->sendWriteRequest(writeUnit, ui->serverEdit->value())) {
        if (!reply->isFinished()) {
            connect(reply, &QModbusReply::finished, this, [this, reply]() {
                if (reply->error() == QModbusDevice::ProtocolError) {
                    statusBar()->showMessage(tr("Write response error: %1 (Mobus exception: 0x%2)")
                        .arg(reply->errorString()).arg(reply->rawResult().exceptionCode(), -1, 16),
                        5000);
                } else if (reply->error() != QModbusDevice::NoError) {
                    statusBar()->showMessage(tr("Write response error: %1 (code: 0x%2)").
                        arg(reply->errorString()).arg(reply->error(), -1, 16), 5000);
                }
                reply->deleteLater();
            });
        } else {
            // broadcast replies return immediately
            reply->deleteLater();
        }
    } else {
        statusBar()->showMessage(tr("Write error: ") + modbusDevice->errorString(), 5000);
    }
}

void MainWindow::on_readWriteButton_clicked()
{
    if (!modbusDevice)
        return;
    ui->readValue->clear();
    statusBar()->clearMessage();

    QModbusDataUnit writeUnit = writeRequest();
    QModbusDataUnit::RegisterType table = writeUnit.registerType();
    for (uint i = 0; i < writeUnit.valueCount(); i++) {
        if (table == QModbusDataUnit::Coils)
            writeUnit.setValue(i, writeModel->m_coils[i + writeUnit.startAddress()]);
        else
            writeUnit.setValue(i, writeModel->m_holdingRegisters[i + writeUnit.startAddress()]);
    }

    if (auto *reply = modbusDevice->sendReadWriteRequest(readRequest(), writeUnit,
        ui->serverEdit->value())) {
        if (!reply->isFinished())
            connect(reply, &QModbusReply::finished, this, &MainWindow::readReady);
        else
            delete reply; // broadcast replies return immediately
    } else {
        statusBar()->showMessage(tr("Read error: ") + modbusDevice->errorString(), 5000);
    }
}

void MainWindow::on_writeTable_currentIndexChanged(int index)
{
    const bool coilsOrHolding = index == 0 || index == 3;
    if (coilsOrHolding) {
        ui->writeValueTable->setColumnHidden(1, index != 0);
        ui->writeValueTable->setColumnHidden(2, index != 3);
        ui->writeValueTable->resizeColumnToContents(0);
    }

    ui->readWriteButton->setEnabled(index == 3);
    ui->writeButton->setEnabled(coilsOrHolding);
    ui->writeGroupBox->setEnabled(coilsOrHolding);
}

QModbusDataUnit MainWindow::readRequest() const
{
    const auto table =
        static_cast<QModbusDataUnit::RegisterType> (ui->writeTable->currentData().toInt());

    int startAddress = ui->readAddress->value();
    Q_ASSERT(startAddress >= 0 && startAddress < 10);

    // do not go beyond 10 entries
    int numberOfEntries = qMin(ui->readSize->currentText().toInt(), 10 - startAddress);
    return QModbusDataUnit(table, startAddress, numberOfEntries);
}

QModbusDataUnit MainWindow::writeRequest() const
{
    const auto table =
        static_cast<QModbusDataUnit::RegisterType> (ui->writeTable->currentData().toInt());

    int startAddress = ui->writeAddress->value();
    Q_ASSERT(startAddress >= 0 && startAddress < 10);

    // do not go beyond 10 entries
    int numberOfEntries = qMin(ui->writeSize->currentText().toInt(), 10 - startAddress);
    return QModbusDataUnit(table, startAddress, numberOfEntries);
}