QObject::connect(ui->spNumOfSamples, SELECT<int>::OVERLOAD_OF(&QSpinBox::valueChanged),

                     this, &MainWindow::onNumOfSamplesChanged);

    QObject::connect(ui->cbAutoScale, &QCheckBox::toggled,

                     this, &MainWindow::onAutoScaleChecked);

    QObject::connect(ui->spYmin, SIGNAL(valueChanged(double)),

                     this, SLOT(onYScaleChanged()));

    QObject::connect(ui->spYmax, SIGNAL(valueChanged(double)),

                     this, SLOT(onYScaleChanged()));

    QObject::connect(ui->actionClear, SIGNAL(triggered(bool)),

                     this, SLOT(clearPlot()));

    // setup number of channels spinbox

    QObject::connect(ui->spNumOfChannels,

                     SELECT<int>::OVERLOAD_OF(&QSpinBox::valueChanged),

                     this, &MainWindow::onNumOfChannelsChanged);

    // setup number format buttons

    numberFormatButtons.addButton(ui->rbUint8,  NumberFormat_uint8);

    numberFormatButtons.addButton(ui->rbUint16, NumberFormat_uint16);

    numberFormatButtons.addButton(ui->rbUint32, NumberFormat_uint32);

    numberFormatButtons.addButton(ui->rbInt8,   NumberFormat_int8);

    numberFormatButtons.addButton(ui->rbInt16,  NumberFormat_int16);

    numberFormatButtons.addButton(ui->rbInt32,  NumberFormat_int32);

    numberFormatButtons.addButton(ui->rbFloat,  NumberFormat_float);

    numberFormatButtons.addButton(ui->rbASCII,  NumberFormat_ASCII);

    QObject::connect(&numberFormatButtons, SIGNAL(buttonToggled(int, bool)),

                     this, SLOT(onNumberFormatButtonToggled(int, bool)));

    // init port signals

    QObject::connect(&(this->serialPort), SIGNAL(error(QSerialPort::SerialPortError)),

                     this, SLOT(onPortError(QSerialPort::SerialPortError)));

    // set limits for axis limit boxes

    ui->spYmin->setRange((-1) * std::numeric_limits<double>::max(),

                         std::numeric_limits<double>::max());

    ui->spYmax->setRange((-1) * std::numeric_limits<double>::max(),

                         std::numeric_limits<double>::max());

    // init data arrays and plot

    numOfSamples = ui->spNumOfSamples->value();

    // init channel data and curve list

    for (unsigned int i = 0; i < numOfChannels; i++)

    {

        channelBuffers.append(new FrameBuffer(numOfSamples));

        curves.append(new QwtPlotCurve());

        curves[i]->setSamples(channelBuffers[i]);

        curves[i]->setPen(makeColor(i));

        curves[i]->attach(ui->plot);

    }

    // init auto scale

    ui->plot->setAxis(ui->cbAutoScale->isChecked(),

                      ui->spYmin->value(), ui->spYmax->value());

    // init grid

    ui->plot->showGrid(ui->actionGrid->isChecked());

    ui->plot->showMinorGrid(ui->actionMinorGrid->isChecked());

    // init number format

    if (numberFormatButtons.checkedId() >= 0)

    {

        selectNumberFormat((NumberFormat) numberFormatButtons.checkedId());

    }

    else

    {

        selectNumberFormat(NumberFormat_uint8);

    }

    // Init sps (sample per second) counter

    sampleCount = 0;

    spsLabel.setText("0sps");

    spsLabel.setToolTip("samples per second (total of all channels)");

    ui->statusBar->addPermanentWidget(&spsLabel);

    spsTimer.start(SPS_UPDATE_TIMEOUT * 1000);

    QObject::connect(&spsTimer, &QTimer::timeout,

                     this, &MainWindow::spsTimerTimeout);

    // Init demo mode

    demoCount = 0;

    demoTimer.setInterval(100);

    QObject::connect(&demoTimer, &QTimer::timeout,

                     this, &MainWindow::demoTimerTimeout);

    QObject::connect(ui->actionDemoMode, &QAction::toggled,

                     this, &MainWindow::enableDemo);

    {   // init demo indicator

        QwtText demoText(" DEMO RUNNING ");  // looks better with spaces