Add Modbus custom function code example

Task-number: QTBUG-91212
Change-Id: I5df9e33186acb5216335ec1010f6694bcbab9376
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

19 files changed, 1868 insertions, 1 deletions

diff --git a/examples/serialbus/modbus/CMakeLists.txt b/examples/serialbus/modbus/CMakeLists.txt
index 8d63950..2e6b6cb 100644
--- a/examples/serialbus/modbus/CMakeLists.txt
+++ b/examples/serialbus/modbus/CMakeLists.txt
@@ -1,5 +1,7 @@
 add_subdirectory(master)
 add_subdirectory(slave)
+add_subdirectory(custom)
+
 if(QT_FEATURE_modbus_serialport)
     add_subdirectory(adueditor)
 endif()
diff --git a/examples/serialbus/modbus/custom/CMakeLists.txt b/examples/serialbus/modbus/custom/CMakeLists.txt
new file mode 100644
index 0000000..cfe398f
--- /dev/null
+++ b/examples/serialbus/modbus/custom/CMakeLists.txt
@@ -0,0 +1,58 @@
+cmake_minimum_required(VERSION 3.14)
+project(customcommand LANGUAGES CXX)
+
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTORCC ON)
+set(CMAKE_AUTOUIC ON)
+
+if(NOT DEFINED INSTALL_EXAMPLESDIR)
+  set(INSTALL_EXAMPLESDIR "examples")
+endif()
+
+set(INSTALL_EXAMPLEDIR "${INSTALL_EXAMPLESDIR}/serialbus/modbus/custom")
+
+find_package(Qt6 COMPONENTS Core)
+find_package(Qt6 COMPONENTS Gui)
+find_package(Qt6 COMPONENTS SerialBus)
+find_package(Qt6 COMPONENTS Widgets)
+
+qt_add_executable(customcommand
+    main.cpp
+    mainwindow.cpp mainwindow.h mainwindow.ui
+    modbusclient.cpp modbusclient.h
+    modbusserver.cpp modbusserver.h
+    registermodel.cpp registermodel.h
+)
+
+set_target_properties(customcommand PROPERTIES
+    WIN32_EXECUTABLE TRUE
+    MACOSX_BUNDLE TRUE
+)
+
+target_link_libraries(customcommand PRIVATE
+    Qt::Core
+    Qt::Gui
+    Qt::SerialBus
+    Qt::Widgets
+)
+
+set(custom_resource_files
+    "images/connect.png"
+    "images/disconnect.png"
+    "images/settings.png"
+)
+
+qt6_add_resources(customcommand "custom"
+    PREFIX
+        "/"
+    FILES
+        ${custom_resource_files}
+)
+
+install(TARGETS customcommand
+    RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
+)
diff --git a/examples/serialbus/modbus/custom/custom.pro b/examples/serialbus/modbus/custom/custom.pro
new file mode 100644
index 0000000..c849c1a
--- /dev/null
+++ b/examples/serialbus/modbus/custom/custom.pro
@@ -0,0 +1,25 @@
+QT += serialbus widgets
+
+TARGET = customcommand
+TEMPLATE = app
+CONFIG += c++11
+
+SOURCES += main.cpp \
+    mainwindow.cpp \
+    modbusclient.cpp \
+    modbusserver.cpp \
+    registermodel.cpp
+
+HEADERS += \
+     mainwindow.h \
+     modbusclient.h \
+     modbusserver.h \
+     registermodel.h
+
+FORMS += \
+    mainwindow.ui
+
+RESOURCES += images.qrc
+
+target.path = $$[QT_INSTALL_EXAMPLES]/serialbus/modbus/custom
+INSTALLS += target
diff --git a/examples/serialbus/modbus/custom/images.qrc b/examples/serialbus/modbus/custom/images.qrc
new file mode 100644
index 0000000..d212059
--- /dev/null
+++ b/examples/serialbus/modbus/custom/images.qrc
@@ -0,0 +1,7 @@
+<RCC>
+  <qresource prefix="/">
+    <file>images/connect.png</file>
+    <file>images/disconnect.png</file>
+    <file>images/settings.png</file>
+  </qresource>
+</RCC>
diff --git a/examples/serialbus/modbus/custom/images/application-exit.png b/examples/serialbus/modbus/custom/images/application-exit.png
new file mode 100644
index 0000000..32be6b3
--- /dev/null
+++ b/examples/serialbus/modbus/custom/images/application-exit.png
diff --git a/examples/serialbus/modbus/custom/images/connect.png b/examples/serialbus/modbus/custom/images/connect.png
new file mode 100644
index 0000000..dd5a51e
--- /dev/null
+++ b/examples/serialbus/modbus/custom/images/connect.png
diff --git a/examples/serialbus/modbus/custom/images/disconnect.png b/examples/serialbus/modbus/custom/images/disconnect.png
new file mode 100644
index 0000000..fd58f7a
--- /dev/null
+++ b/examples/serialbus/modbus/custom/images/disconnect.png
diff --git a/examples/serialbus/modbus/custom/images/settings.png b/examples/serialbus/modbus/custom/images/settings.png
new file mode 100644
index 0000000..3d1042e
--- /dev/null
+++ b/examples/serialbus/modbus/custom/images/settings.png
diff --git a/examples/serialbus/modbus/custom/main.cpp b/examples/serialbus/modbus/custom/main.cpp
new file mode 100644
index 0000000..f42e918
--- /dev/null
+++ b/examples/serialbus/modbus/custom/main.cpp
@@ -0,0 +1,66 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "mainwindow.h"
+
+#include <QApplication>
+#include <QLoggingCategory>
+
+int main(int argc, char *argv[])
+{
+    // Uncomment the following line to enable logging
+    // QLoggingCategory::setFilterRules(QStringLiteral("qt.modbus* = true"));
+
+    QApplication a(argc, argv);
+    MainWindow w;
+    w.show();
+
+    return a.exec();
+}
diff --git a/examples/serialbus/modbus/custom/mainwindow.cpp b/examples/serialbus/modbus/custom/mainwindow.cpp
new file mode 100644
index 0000000..cd93d78
--- /dev/null
+++ b/examples/serialbus/modbus/custom/mainwindow.cpp
@@ -0,0 +1,314 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "mainwindow.h"
+#include "registermodel.h"
+#include "ui_mainwindow.h"
+
+#include <QtWidgets>
+#include <QtSerialBus>
+
+MainWindow::MainWindow(QWidget* parent)
+    : QMainWindow(parent)
+    , ui(new Ui::MainWindow)
+{
+    ui->setupUi(this);
+    ui->statusbar->setSizeGripEnabled(false);
+
+    setupConnections();
+    setupClientContainer();
+    setupServerContainer();
+}
+
+MainWindow::~MainWindow()
+{
+    m_client.disconnectDevice();
+    m_server.disconnectDevice();
+
+    delete ui;
+}
+
+void MainWindow::setupConnections()
+{
+    // actions
+    connect(ui->actionConnect, &QAction::triggered, this, &MainWindow::onConnectButtonClicked);
+    connect(ui->actionDisconnect, &QAction::triggered, this, &MainWindow::onConnectButtonClicked);
+    connect(ui->actionExit, &QAction::triggered, this, &QMainWindow::close);
+
+    // buttons
+    connect(ui->readButton, &QPushButton::clicked, this, &MainWindow::onReadButtonClicked);
+    connect(ui->writeButton, &QPushButton::clicked, this, &MainWindow::onWriteButtonClicked);
+    connect(ui->connectButton, &QPushButton::clicked, this, &MainWindow::onConnectButtonClicked);
+
+    // client
+    connect(&m_client, &QModbusServer::stateChanged, this, &MainWindow::onStateChanged);
+    connect(&m_client, &QModbusServer::errorOccurred, [this](QModbusDevice::Error) {
+        statusBar()->showMessage(m_client.errorString(), 5000);
+    });
+
+    // server
+    connect(&m_server, &QModbusServer::dataWritten, this, &MainWindow::updateWidgets);
+    connect(&m_server, &QModbusServer::errorOccurred, [this](QModbusDevice::Error) {
+        statusBar()->showMessage(m_server.errorString(), 5000);
+    });
+}
+
+void MainWindow::onConnectButtonClicked()
+{
+    bool intendToConnect = (m_server.state() == QModbusDevice::UnconnectedState
+        && m_client.state() == QModbusDevice::UnconnectedState);
+
+    if (intendToConnect) {
+        const QUrl url = QUrl::fromUserInput(ui->addressPort->text());
+        m_server.setConnectionParameter(QModbusDevice::NetworkPortParameter, url.port());
+        m_server.setConnectionParameter(QModbusDevice::NetworkAddressParameter, url.host());
+        m_server.setServerAddress(ui->serverAddress->text().toInt());
+
+        if (m_server.connectDevice()) {
+            m_client.setConnectionParameter(QModbusDevice::NetworkPortParameter, url.port());
+            m_client.setConnectionParameter(QModbusDevice::NetworkAddressParameter, url.host());
+
+            if (m_client.connectDevice()) {
+                ui->actionConnect->setEnabled(false);
+                ui->actionDisconnect->setEnabled(true);
+            } else {
+                statusBar()->showMessage(tr("Client connect failed: ") + m_client.errorString(), 5000);
+            }
+        } else {
+            statusBar()->showMessage(tr("Server connect failed: ") + m_server.errorString(), 5000);
+        }
+    } else {
+        m_client.disconnectDevice();
+        m_server.disconnectDevice();
+        ui->actionConnect->setEnabled(true);
+        ui->actionDisconnect->setEnabled(false);
+    }
+}
+
+void MainWindow::onStateChanged(int state)
+{
+    ui->serverAddress->setEnabled(state == QModbusDevice::UnconnectedState);
+    ui->actionConnect->setEnabled(state == QModbusDevice::UnconnectedState);
+    ui->actionDisconnect->setEnabled(state == QModbusDevice::ConnectedState);
+
+    if (state == QModbusDevice::UnconnectedState)
+        ui->connectButton->setText(tr("Connect"));
+    else if (state == QModbusDevice::ConnectedState)
+        ui->connectButton->setText(tr("Disconnect"));
+}
+
+// -- client
+
+void MainWindow::onReadReady()
+{
+    auto reply = qobject_cast<QModbusReply*>(sender());
+    if (!reply)
+        return;
+
+    if (reply->error() == QModbusDevice::NoError) {
+        const QModbusDataUnit unit = reply->result();
+        for (int i = 0, total = int(unit.valueCount()); i < total; ++i) {
+            auto st = unit.startAddress();
+            m_model->setData(m_model->index(unit.startAddress() + i, 1),
+                QString::number(unit.value(i), 16), Qt::EditRole);
+        }
+    } else if (reply->error() == QModbusDevice::ProtocolError) {
+        statusBar()->showMessage(tr("Read response error: %1 (Modbus 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::onReadButtonClicked()
+{
+    QModbusRequest readRequest {
+        QModbusPdu::FunctionCode(ModbusClient::CustomRead),
+        quint16(ui->startAddress->value()),
+        qMin(ui->numberOfRegisters->currentText().toUShort(),
+            quint16(10 - ui->startAddress->value())) // do not go beyond 10 entries
+    };
+
+    if (auto* reply = m_client.sendRawRequest(readRequest, ui->serverAddress->value())) {
+        if (!reply->isFinished())
+            connect(reply, &QModbusReply::finished, this, &MainWindow::onReadReady);
+    } else {
+        statusBar()->showMessage(tr("Read error: ") + m_client.errorString(), 5000);
+    }
+}
+
+void MainWindow::onWriteButtonClicked()
+{
+    QModbusDataUnit unit {
+        QModbusDataUnit::HoldingRegisters,
+        ui->startAddress->value(),
+        qMin(ui->numberOfRegisters->currentText().toUShort(),
+            quint16(10 - ui->startAddress->value())) // do not go beyond 10 entries
+    };
+
+    for (qsizetype i = 0, total = int(unit.valueCount()); i < total; ++i)
+        unit.setValue(i, m_model->m_registers[i + unit.startAddress()]);
+
+    const quint8 byteCount = unit.valueCount() * 2;
+    QModbusRequest writeRequest {
+        QModbusPdu::FunctionCode(ModbusClient::CustomWrite),
+        quint16(unit.startAddress()),
+        quint16(unit.valueCount()), byteCount, unit.values()
+    };
+
+    if (auto *reply = m_client.sendRawRequest(writeRequest, ui->serverAddress->value())) {
+        if (!reply->isFinished()) {
+            connect(reply, &QModbusReply::finished, this, [this, reply]() {
+                if (reply->error() == QModbusDevice::ProtocolError) {
+                    statusBar()->showMessage(tr("Write response error: %1 (Modbus 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 {
+        statusBar()->showMessage(tr("Write error: ") + m_client.errorString(), 5000);
+    }
+}
+
+void MainWindow::setupClientContainer()
+{
+    m_model = new RegisterModel(this);
+    m_model->setStartAddress(ui->startAddress->value());
+    m_model->setNumberOfValues(ui->numberOfRegisters->currentText());
+
+    ui->registersTable->setModel(m_model);
+    connect(m_model, &RegisterModel::updateViewport, ui->registersTable->viewport(),
+        QOverload<>::of(&QWidget::update));
+
+    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->numberOfRegisters->setModel(model);
+    ui->numberOfRegisters->setCurrentText("10");
+    connect(ui->numberOfRegisters, &QComboBox::currentTextChanged,
+        m_model, &RegisterModel::setNumberOfValues);
+
+    connect(ui->startAddress, &QSpinBox::valueChanged, m_model, &RegisterModel::setStartAddress);
+    connect(ui->startAddress, &QSpinBox::valueChanged, this, [this, model](int i) {
+        int lastPossibleIndex = 0;
+        const int currentIndex = ui->numberOfRegisters->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->numberOfRegisters->setCurrentIndex(lastPossibleIndex);
+        }
+    );
+}
+
+// -- server
+
+void MainWindow::setRegister(const QString &value)
+{
+    const QString objectName = QObject::sender()->objectName();
+    if (m_registers.contains(objectName)) {
+        const quint16 id = quint16(QObject::sender()->property("ID").toUInt());
+
+        bool ok = false;
+        ok = m_server.setData(QModbusDataUnit::HoldingRegisters, id, value.toUShort(&ok, 16));
+        if (!ok)
+            statusBar()->showMessage(tr("Could not set register: ") + m_server.errorString(), 5000);
+    }
+}
+
+void MainWindow::updateWidgets(QModbusDataUnit::RegisterType table, int address, int size)
+{
+    if (table != QModbusDataUnit::HoldingRegisters)
+        return;
+
+    QString text;
+    quint16 value;
+    for (int i = 0; i < size; ++i) {
+        m_server.data(table, quint16(address + i), &value);
+        m_registers.value(QStringLiteral("register_%1").arg(address + i))->setText(text.setNum(value, 16));
+    }
+}
+
+void MainWindow::setupServerContainer()
+{
+    QRegularExpression regexp(QStringLiteral("register_(?<ID>\\d+)"));
+    const QList<QLineEdit *> qle = ui->server->findChildren<QLineEdit *>(regexp);
+    for (QLineEdit *lineEdit : qle) {
+        const quint16 id = regexp.match(lineEdit->objectName()).captured(QStringLiteral("ID")).toInt();
+
+        lineEdit->setProperty("ID", id);
+        m_registers.insert(lineEdit->objectName(), lineEdit);
+        lineEdit->setValidator(new QRegularExpressionValidator(
+            QRegularExpression(QStringLiteral("[0-9a-f]{0,4}"), QRegularExpression::CaseInsensitiveOption),
+            this)
+        );
+
+        bool ok;
+        m_server.setData(QModbusDataUnit::HoldingRegisters, id, lineEdit->text().toUShort(&ok, 16));
+        connect(lineEdit, &QLineEdit::textChanged, this, &MainWindow::setRegister);
+    }
+}
diff --git a/examples/serialbus/modbus/custom/mainwindow.h b/examples/serialbus/modbus/custom/mainwindow.h
new file mode 100644
index 0000000..e538da3
--- /dev/null
+++ b/examples/serialbus/modbus/custom/mainwindow.h
@@ -0,0 +1,105 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef MAINWINDOW_H
+#define MAINWINDOW_H
+
+#include "modbusclient.h"
+#include "modbusserver.h"
+
+#include <QHash>
+#include <QMainWindow>
+
+QT_BEGIN_NAMESPACE
+
+class QLineEdit;
+
+namespace Ui {
+class MainWindow;
+}
+
+QT_END_NAMESPACE
+
+class RegisterModel;
+
+class MainWindow : public QMainWindow
+{
+    Q_OBJECT
+
+public:
+    explicit MainWindow(QWidget *parent = nullptr);
+    ~MainWindow();
+
+private Q_SLOTS:
+    void onConnectButtonClicked();
+    void onStateChanged(int state);
+
+    void onReadReady();
+    void onReadButtonClicked();
+    void onWriteButtonClicked();
+
+    void setRegister(const QString &value);
+    void updateWidgets(QModbusDataUnit::RegisterType table, int address, int size);
+
+private:
+    void setupConnections();
+    void setupClientContainer();
+    void setupServerContainer();
+
+private:
+    Ui::MainWindow *ui = nullptr;
+    RegisterModel *m_model = nullptr;
+
+    ModbusClient m_client;
+    ModbusServer m_server;
+    QHash<QString, QLineEdit *> m_registers;
+};
+
+#endif // MAINWINDOW_H
diff --git a/examples/serialbus/modbus/custom/mainwindow.ui b/examples/serialbus/modbus/custom/mainwindow.ui
new file mode 100644
index 0000000..d8e6099
--- /dev/null
+++ b/examples/serialbus/modbus/custom/mainwindow.ui
@@ -0,0 +1,650 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>MainWindow</class>
+ <widget class="QMainWindow" name="MainWindow">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>620</width>
+    <height>482</height>
+   </rect>
+  </property>
+  <property name="sizePolicy">
+   <sizepolicy hsizetype="Preferred" vsizetype="Preferred">
+    <horstretch>0</horstretch>
+    <verstretch>0</verstretch>
+   </sizepolicy>
+  </property>
+  <property name="windowTitle">
+   <string>MainWindow</string>
+  </property>
+  <widget class="QWidget" name="centralwidget">
+   <layout class="QGridLayout" name="gridLayout_3">
+    <item row="0" column="0">
+     <layout class="QGridLayout" name="gridLayout">
+      <item row="0" column="0">
+       <widget class="QLabel" name="label_4">
+        <property name="text">
+         <string>Address &amp; Port:</string>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="1">
+       <widget class="QLineEdit" name="addressPort">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="MinimumExpanding" vsizetype="Fixed">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="text">
+         <string>127.0.0.1:502</string>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="2">
+       <spacer name="horizontalSpacer_2">
+        <property name="orientation">
+         <enum>Qt::Horizontal</enum>
+        </property>
+        <property name="sizeType">
+         <enum>QSizePolicy::Maximum</enum>
+        </property>
+        <property name="sizeHint" stdset="0">
+         <size>
+          <width>13</width>
+          <height>17</height>
+         </size>
+        </property>
+       </spacer>
+      </item>
+      <item row="0" column="3">
+       <widget class="QLabel" name="label_28">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Maximum" vsizetype="Preferred">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="text">
+         <string>Server Address:</string>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="4">
+       <widget class="QSpinBox" name="serverAddress">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Maximum" vsizetype="Fixed">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="minimum">
+         <number>1</number>
+        </property>
+        <property name="maximum">
+         <number>247</number>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="5">
+       <widget class="QPushButton" name="connectButton">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Maximum" vsizetype="Fixed">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="text">
+         <string>Connect</string>
+        </property>
+        <property name="checkable">
+         <bool>false</bool>
+        </property>
+        <property name="autoDefault">
+         <bool>false</bool>
+        </property>
+        <property name="default">
+         <bool>true</bool>
+        </property>
+       </widget>
+      </item>
+      <item row="1" column="0" colspan="6">
+       <widget class="Line" name="line">
+        <property name="orientation">
+         <enum>Qt::Horizontal</enum>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </item>
+    <item row="1" column="0">
+     <layout class="QGridLayout" name="gridLayout_2">
+      <item row="0" column="0">
+       <widget class="QLabel" name="label">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Maximum" vsizetype="Preferred">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="text">
+         <string>Custom Function code (Read):</string>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="1">
+       <widget class="QLabel" name="label_9">
+        <property name="font">
+         <font>
+          <bold>true</bold>
+         </font>
+        </property>
+        <property name="text">
+         <string>0X41</string>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="2" rowspan="2">
+       <spacer name="horizontalSpacer">
+        <property name="orientation">
+         <enum>Qt::Horizontal</enum>
+        </property>
+        <property name="sizeType">
+         <enum>QSizePolicy::Fixed</enum>
+        </property>
+        <property name="sizeHint" stdset="0">
+         <size>
+          <width>40</width>
+          <height>20</height>
+         </size>
+        </property>
+       </spacer>
+      </item>
+      <item row="0" column="3" rowspan="2">
+       <widget class="QLabel" name="label_7">
+        <property name="text">
+         <string>The Modbus specification reserves two ranges of user-defined function codes, i.e. 0x41 to 0x48 and from 0x64 to 0x6e.</string>
+        </property>
+        <property name="wordWrap">
+         <bool>true</bool>
+        </property>
+       </widget>
+      </item>
+      <item row="1" column="0">
+       <widget class="QLabel" name="label_2">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Maximum" vsizetype="Preferred">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="text">
+         <string>Custom Function code (Write):</string>
+        </property>
+       </widget>
+      </item>
+      <item row="1" column="1">
+       <widget class="QLabel" name="label_10">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Maximum" vsizetype="Preferred">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="font">
+         <font>
+          <bold>true</bold>
+         </font>
+        </property>
+        <property name="text">
+         <string>0X42</string>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </item>
+    <item row="2" column="0">
+     <layout class="QHBoxLayout" name="horizontalLayout_2">
+      <item>
+       <widget class="QGroupBox" name="server">
+        <property name="title">
+         <string>Server</string>
+        </property>
+        <layout class="QFormLayout" name="formLayout_2">
+         <item row="0" column="0">
+          <widget class="QLabel" name="address">
+           <property name="sizePolicy">
+            <sizepolicy hsizetype="Maximum" vsizetype="Preferred">
+             <horstretch>0</horstretch>
+             <verstretch>0</verstretch>
+            </sizepolicy>
+           </property>
+           <property name="text">
+            <string>Address</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="0" column="1">
+          <widget class="QLabel" name="label_3">
+           <property name="text">
+            <string>Registers</string>
+           </property>
+          </widget>
+         </item>
+         <item row="1" column="0">
+          <widget class="QLabel" name="label_21">
+           <property name="text">
+            <string>0</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="1" column="1">
+          <widget class="QLineEdit" name="register_0">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="2" column="0">
+          <widget class="QLabel" name="label_22">
+           <property name="text">
+            <string>1</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="2" column="1">
+          <widget class="QLineEdit" name="register_1">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="3" column="0">
+          <widget class="QLabel" name="label_23">
+           <property name="text">
+            <string>2</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="3" column="1">
+          <widget class="QLineEdit" name="register_2">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="4" column="0">
+          <widget class="QLabel" name="label_11">
+           <property name="text">
+            <string>3</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="4" column="1">
+          <widget class="QLineEdit" name="register_3">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="5" column="0">
+          <widget class="QLabel" name="label_8">
+           <property name="text">
+            <string>4</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="5" column="1">
+          <widget class="QLineEdit" name="register_4">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="6" column="0">
+          <widget class="QLabel" name="label_12">
+           <property name="text">
+            <string>5</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="6" column="1">
+          <widget class="QLineEdit" name="register_5">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="7" column="0">
+          <widget class="QLabel" name="label_13">
+           <property name="text">
+            <string>6</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="7" column="1">
+          <widget class="QLineEdit" name="register_6">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="8" column="0">
+          <widget class="QLabel" name="label_14">
+           <property name="text">
+            <string>7</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="8" column="1">
+          <widget class="QLineEdit" name="register_7">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="9" column="0">
+          <widget class="QLabel" name="label_15">
+           <property name="text">
+            <string>8</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="9" column="1">
+          <widget class="QLineEdit" name="register_8">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+         <item row="10" column="0">
+          <widget class="QLabel" name="label_16">
+           <property name="text">
+            <string>9</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+          </widget>
+         </item>
+         <item row="10" column="1">
+          <widget class="QLineEdit" name="register_9">
+           <property name="maxLength">
+            <number>32767</number>
+           </property>
+           <property name="placeholderText">
+            <string>Hexadecimal A-F, a-f, 0-9.</string>
+           </property>
+          </widget>
+         </item>
+        </layout>
+       </widget>
+      </item>
+      <item>
+       <widget class="QGroupBox" name="groupBox">
+        <property name="title">
+         <string>Client</string>
+        </property>
+        <layout class="QFormLayout" name="formLayout">
+         <item row="0" column="0">
+          <widget class="QLabel" name="label_5">
+           <property name="text">
+            <string>Start address:</string>
+           </property>
+          </widget>
+         </item>
+         <item row="0" column="1">
+          <widget class="QSpinBox" name="startAddress">
+           <property name="maximum">
+            <number>9</number>
+           </property>
+          </widget>
+         </item>
+         <item row="1" column="0">
+          <widget class="QLabel" name="label_6">
+           <property name="text">
+            <string>Number of registers:</string>
+           </property>
+          </widget>
+         </item>
+         <item row="1" column="1">
+          <widget class="QComboBox" name="numberOfRegisters">
+           <property name="currentIndex">
+            <number>9</number>
+           </property>
+           <item>
+            <property name="text">
+             <string>1</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>2</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>3</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>4</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>5</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>6</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>7</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>8</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>9</string>
+            </property>
+           </item>
+           <item>
+            <property name="text">
+             <string>10</string>
+            </property>
+           </item>
+          </widget>
+         </item>
+         <item row="2" column="0" colspan="2">
+          <widget class="QTreeView" name="registersTable">
+           <property name="showDropIndicator" stdset="0">
+            <bool>true</bool>
+           </property>
+           <property name="alternatingRowColors">
+            <bool>true</bool>
+           </property>
+           <property name="rootIsDecorated">
+            <bool>false</bool>
+           </property>
+           <property name="uniformRowHeights">
+            <bool>true</bool>
+           </property>
+           <property name="itemsExpandable">
+            <bool>false</bool>
+           </property>
+           <property name="expandsOnDoubleClick">
+            <bool>false</bool>
+           </property>
+           <attribute name="headerVisible">
+            <bool>true</bool>
+           </attribute>
+          </widget>
+         </item>
+         <item row="3" column="0" colspan="2">
+          <layout class="QHBoxLayout" name="horizontalLayout">
+           <item>
+            <spacer name="horizontalSpacer_3">
+             <property name="orientation">
+              <enum>Qt::Horizontal</enum>
+             </property>
+             <property name="sizeHint" stdset="0">
+              <size>
+               <width>13</width>
+               <height>17</height>
+              </size>
+             </property>
+            </spacer>
+           </item>
+           <item>
+            <widget class="QPushButton" name="readButton">
+             <property name="sizePolicy">
+              <sizepolicy hsizetype="Maximum" vsizetype="Fixed">
+               <horstretch>0</horstretch>
+               <verstretch>0</verstretch>
+              </sizepolicy>
+             </property>
+             <property name="text">
+              <string>Read</string>
+             </property>
+            </widget>
+           </item>
+           <item>
+            <widget class="QPushButton" name="writeButton">
+             <property name="text">
+              <string>Write</string>
+             </property>
+            </widget>
+           </item>
+          </layout>
+         </item>
+        </layout>
+       </widget>
+      </item>
+     </layout>
+    </item>
+   </layout>
+  </widget>
+  <widget class="QMenuBar" name="menubar">
+   <property name="geometry">
+    <rect>
+     <x>0</x>
+     <y>0</y>
+     <width>620</width>
+     <height>22</height>
+    </rect>
+   </property>
+   <widget class="QMenu" name="menuDevice">
+    <property name="title">
+     <string>Device</string>
+    </property>
+    <addaction name="actionConnect"/>
+    <addaction name="actionDisconnect"/>
+    <addaction name="separator"/>
+    <addaction name="actionExit"/>
+   </widget>
+   <addaction name="menuDevice"/>
+  </widget>
+  <widget class="QStatusBar" name="statusbar"/>
+  <action name="actionExit">
+   <property name="text">
+    <string>Quit</string>
+   </property>
+  </action>
+  <action name="actionConnect">
+   <property name="enabled">
+    <bool>true</bool>
+   </property>
+   <property name="icon">
+    <iconset resource="images.qrc">
+     <normaloff>:/images/connect.png</normaloff>:/images/connect.png</iconset>
+   </property>
+   <property name="text">
+    <string>Connect</string>
+   </property>
+  </action>
+  <action name="actionDisconnect">
+   <property name="enabled">
+    <bool>false</bool>
+   </property>
+   <property name="icon">
+    <iconset resource="images.qrc">
+     <normaloff>:/images/disconnect.png</normaloff>:/images/disconnect.png</iconset>
+   </property>
+   <property name="text">
+    <string>Disconnect</string>
+   </property>
+  </action>
+ </widget>
+ <resources>
+  <include location="images.qrc"/>
+ </resources>
+ <connections/>
+</ui>
diff --git a/examples/serialbus/modbus/custom/modbusclient.cpp b/examples/serialbus/modbus/custom/modbusclient.cpp
new file mode 100644
index 0000000..faba17f
--- /dev/null
+++ b/examples/serialbus/modbus/custom/modbusclient.cpp
@@ -0,0 +1,134 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "modbusclient.h"
+
+// The read response must contain the start address (quint16), the byte count
+// (quint8) and at least one register value (quint16).
+static constexpr int ReadHeaderSize {3};
+static constexpr int MinimumReadResponseSize {ReadHeaderSize + 2}; // 2 payload bytes
+
+// The response must contain the start address (quint16) and the number of
+// registers written (quint16).
+static constexpr int WriteResponseSize {4};
+
+ModbusClient::ModbusClient(QObject *parent)
+    : QModbusTcpClient(parent)
+{
+    QModbusResponse::registerDataSizeCalculator(CustomRead, [](const QModbusResponse &response) {
+        if (!response.isValid())
+            return -1;
+
+        if (response.dataSize() < MinimumReadResponseSize)
+            return -1;
+        return ReadHeaderSize + quint8(response.data().at(ReadHeaderSize - 1));
+    });
+
+    QModbusResponse::registerDataSizeCalculator(CustomWrite, [](const QModbusResponse &response) {
+        if (!response.isValid())
+            return -1;
+        return (response.dataSize() != WriteResponseSize ? -1 : WriteResponseSize);
+    });
+}
+
+static bool collateBytes(const QModbusPdu &response, QModbusDataUnit *data)
+{
+    if (response.dataSize() < MinimumReadResponseSize)
+        return false;
+
+    quint16 address; quint8 byteCount;
+    response.decodeData(&address, &byteCount);
+
+    if (byteCount % 2 != 0)
+        return false;
+
+    if (data) {
+        QDataStream stream(response.data().remove(0, 3));
+
+        QList<quint16> values;
+        const quint8 itemCount = byteCount / 2;
+        for (int i = 0; i < itemCount; i++) {
+            quint16 tmp;
+            stream >> tmp;
+            values.append(tmp);
+        }
+        *data = {QModbusDataUnit::HoldingRegisters, address, values};
+    }
+    return true;
+}
+
+static bool collateMultipleValues(const QModbusPdu &response, QModbusDataUnit *data)
+{
+    if (response.dataSize() != WriteResponseSize)
+        return false;
+
+    quint16 address, count;
+    response.decodeData(&address, &count);
+
+    if (count < 1 || count > 10)
+        return false;
+
+    if (data)
+        *data = {QModbusDataUnit::HoldingRegisters, address, count};
+    return true;
+}
+
+bool ModbusClient::processPrivateResponse(const QModbusResponse &response, QModbusDataUnit *data)
+{
+    if (!response.isValid())
+        return QModbusClient::processPrivateResponse(response, data);
+
+    if (CustomRead == response.functionCode())
+        return collateBytes(response, data);
+
+    if (CustomWrite == response.functionCode())
+        return collateMultipleValues(response, data);
+    return QModbusClient::processPrivateResponse(response, data);
+}
diff --git a/examples/serialbus/modbus/custom/modbusclient.h b/examples/serialbus/modbus/custom/modbusclient.h
new file mode 100644
index 0000000..a803839
--- /dev/null
+++ b/examples/serialbus/modbus/custom/modbusclient.h
@@ -0,0 +1,71 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QModbusTcpClient>
+
+#ifndef MODBUSCLIENT_H
+#define MODBUSCLIENT_H
+
+class ModbusClient : public QModbusTcpClient
+{
+    Q_OBJECT
+    Q_DISABLE_COPY_MOVE(ModbusClient)
+
+public:
+    ModbusClient(QObject *parent = nullptr);
+
+    static constexpr QModbusPdu::FunctionCode CustomRead {QModbusPdu::FunctionCode(0x41)};
+    static constexpr QModbusPdu::FunctionCode CustomWrite {QModbusPdu::FunctionCode(0x42)};
+
+private:
+    bool processPrivateResponse(const QModbusResponse &response, QModbusDataUnit *data) override;
+};
+
+#endif // MODBUSCLIENT_H
diff --git a/examples/serialbus/modbus/custom/modbusserver.cpp b/examples/serialbus/modbus/custom/modbusserver.cpp
new file mode 100644
index 0000000..e80a472
--- /dev/null
+++ b/examples/serialbus/modbus/custom/modbusserver.cpp
@@ -0,0 +1,131 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "modbusserver.h"
+#include "modbusclient.h"
+
+// The request must contain the start address (quint16) and the number of
+// registers to read (quint16).
+static constexpr int ReadRequestSize {4};
+
+// The request must contain the start address (quint16), the number of
+// registers to write (quint16), the byte count (quint8) and at least one
+// register value (quint16).
+static constexpr int WriteHeaderSize {5};
+static constexpr int MinimumWriteRequestSize {WriteHeaderSize + 2}; // 2 payload bytes
+
+ModbusServer::ModbusServer(QObject *parent)
+    : QModbusTcpServer(parent)
+{
+    setMap({{QModbusDataUnit::HoldingRegisters, {QModbusDataUnit::HoldingRegisters, 0, 10}}});
+
+    QModbusRequest::registerDataSizeCalculator(ModbusClient::CustomRead, [](const QModbusRequest &request) {
+        if (!request.isValid())
+            return -1;
+        return (request.dataSize() != ReadRequestSize ? -1 : ReadRequestSize);
+    });
+
+    QModbusRequest::registerDataSizeCalculator(ModbusClient::CustomWrite, [](const QModbusRequest &request) {
+        if (!request.isValid())
+            return -1;
+
+        if (request.dataSize() < MinimumWriteRequestSize)
+            return -1;
+        return WriteHeaderSize + quint8(request.data().at(WriteHeaderSize - 1));
+    });
+}
+
+QModbusResponse ModbusServer::processPrivateRequest(const QModbusPdu &request)
+{
+    if (!request.isValid())
+        return QModbusServer::processPrivateRequest(request);
+
+    if (ModbusClient::CustomRead == request.functionCode()) {
+        quint16 startAddress, count;
+        request.decodeData(&startAddress, &count);
+
+        QModbusDataUnit unit(QModbusDataUnit::HoldingRegisters, startAddress, count);
+        if (!data(&unit)) {
+            return QModbusExceptionResponse(request.functionCode(),
+                QModbusExceptionResponse::IllegalDataAddress);
+        }
+        return QModbusResponse(request.functionCode(), startAddress, quint8(count * 2), unit.values());
+    }
+
+    if (ModbusClient::CustomWrite == request.functionCode()) {
+        quint8 byteCount;
+        quint16 startAddress, numberOfRegisters;
+        request.decodeData(&startAddress, &numberOfRegisters, &byteCount);
+
+        if (byteCount % 2 != 0) {
+            return QModbusExceptionResponse(request.functionCode(),
+                QModbusExceptionResponse::IllegalDataValue);
+        }
+
+        const QByteArray pduData = request.data().remove(0, WriteHeaderSize);
+        QDataStream stream(pduData);
+
+        QList<quint16> values;
+        for (int i = 0; i < numberOfRegisters; i++) {
+            quint16 tmp;
+            stream >> tmp;
+            values.append(tmp);
+        }
+
+        if (!writeData({QModbusDataUnit::HoldingRegisters, startAddress, values})) {
+            return QModbusExceptionResponse(request.functionCode(),
+                QModbusExceptionResponse::ServerDeviceFailure);
+        }
+
+        return QModbusResponse(request.functionCode(), startAddress, numberOfRegisters);
+    }
+
+    return QModbusServer::processPrivateRequest(request);
+}
diff --git a/examples/serialbus/modbus/custom/modbusserver.h b/examples/serialbus/modbus/custom/modbusserver.h
new file mode 100644
index 0000000..cae690e
--- /dev/null
+++ b/examples/serialbus/modbus/custom/modbusserver.h
@@ -0,0 +1,68 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QModbusTcpServer>
+
+#ifndef MODBUSSERVER_H
+#define MODBUSSERVER_H
+
+class ModbusServer : public QModbusTcpServer
+{
+    Q_OBJECT
+    Q_DISABLE_COPY_MOVE(ModbusServer)
+
+public:
+    ModbusServer(QObject *parent = nullptr);
+
+private:
+    QModbusResponse processPrivateRequest(const QModbusPdu &request) override;
+};
+
+#endif // MODBUSSERVER_H
diff --git a/examples/serialbus/modbus/custom/registermodel.cpp b/examples/serialbus/modbus/custom/registermodel.cpp
new file mode 100644
index 0000000..7e0f52f
--- /dev/null
+++ b/examples/serialbus/modbus/custom/registermodel.cpp
@@ -0,0 +1,150 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "registermodel.h"
+
+enum { NumColumn = 0, RegistersColumn = 1, ColumnCount = 2, RowCount = 10 };
+
+RegisterModel::RegisterModel(QObject *parent)
+    : QAbstractTableModel(parent)
+    , m_registers(RowCount, 0u)
+{
+}
+
+int RegisterModel::rowCount(const QModelIndex &/*parent*/) const
+{
+    return RowCount;
+}
+
+int RegisterModel::columnCount(const QModelIndex &/*parent*/) const
+{
+    return ColumnCount;
+}
+
+QVariant RegisterModel::data(const QModelIndex &index, int role) const
+{
+    if (!index.isValid() || index.row() >= RowCount || index.column() >= ColumnCount)
+        return QVariant();
+
+    Q_ASSERT(m_registers.count() == RowCount);
+
+    if (index.column() == NumColumn && role == Qt::DisplayRole)
+        return QString::number(index.row());
+
+    if (index.column() == RegistersColumn && role == Qt::DisplayRole)
+        return QString("0x%1").arg(QString::number(m_registers.at(index.row()), 16));
+
+    return QVariant();
+}
+
+QVariant RegisterModel::headerData(int section, Qt::Orientation orientation, int role) const
+{
+    if (role != Qt::DisplayRole)
+        return QVariant();
+
+    if (orientation == Qt::Horizontal) {
+        switch (section) {
+        case NumColumn:
+            return tr("Address");
+        case RegistersColumn:
+            return tr("Registers");
+        default:
+            break;
+        }
+    }
+    return QVariant();
+}
+
+bool RegisterModel::setData(const QModelIndex &index, const QVariant &value, int role)
+{
+    if (!index.isValid() ||  index.row() >= RowCount || index.column() >= ColumnCount)
+        return false;
+
+    Q_ASSERT(m_registers.count() == RowCount);
+
+    if (index.column() == RegistersColumn && role == Qt::EditRole) {
+        bool result = false;
+        quint16 newValue = value.toString().toUShort(&result, 16);
+        if (result)
+            m_registers[index.row()] = newValue;
+
+        emit dataChanged(index, index);
+        return result;
+    }
+
+    return false;
+}
+
+Qt::ItemFlags RegisterModel::flags(const QModelIndex &index) const
+{
+    if (!index.isValid() || index.row() >= RowCount || index.column() >= ColumnCount)
+        return QAbstractTableModel::flags(index);
+
+    Qt::ItemFlags flags = QAbstractTableModel::flags(index);
+    if ((index.row() < m_address) || (index.row() >= (m_address + m_number)))
+        flags &= ~Qt::ItemIsEnabled;
+
+    if (index.column() == RegistersColumn)
+        return flags | Qt::ItemIsEditable;
+
+    return flags;
+}
+
+void RegisterModel::setStartAddress(int address)
+{
+    m_address = address;
+    emit updateViewport();
+}
+
+void RegisterModel::setNumberOfValues(const QString &number)
+{
+    m_number = number.toInt();
+    emit updateViewport();
+}
diff --git a/examples/serialbus/modbus/custom/registermodel.h b/examples/serialbus/modbus/custom/registermodel.h
new file mode 100644
index 0000000..1c06ddd
--- /dev/null
+++ b/examples/serialbus/modbus/custom/registermodel.h
@@ -0,0 +1,85 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtSerialBus module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef REGISTERMODEL_H
+#define REGISTERMODEL_H
+
+#include <QAbstractItemModel>
+
+class RegisterModel : public QAbstractTableModel
+{
+    Q_OBJECT
+
+public:
+    RegisterModel(QObject *parent = nullptr);
+
+    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
+    int columnCount(const QModelIndex &parent = QModelIndex()) const override;
+
+    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
+    QVariant headerData(int section, Qt::Orientation orientation, int role) const override;
+    bool setData(const QModelIndex &index, const QVariant &value, int role) override;
+
+    Qt::ItemFlags flags(const QModelIndex &index) const override;
+
+public slots:
+    void setStartAddress(int address);
+    void setNumberOfValues(const QString &number);
+
+signals:
+    void updateViewport();
+
+public:
+    int m_number = 0;
+    int m_address = 0;
+    QList<quint16> m_registers;
+};
+
+#endif // REGISTERMODEL_H
diff --git a/examples/serialbus/modbus/modbus.pro b/examples/serialbus/modbus/modbus.pro
index a15b828..9e94be7 100644
--- a/examples/serialbus/modbus/modbus.pro
+++ b/examples/serialbus/modbus/modbus.pro
@@ -3,4 +3,5 @@ TEMPLATE = subdirs
 SUBDIRS += \
     master \
     slave \
-    adueditor
+    adueditor \
+    custom