Can't locate devices with QtBluetooth low energy

[Sucharek]

Hi, I'm trying to scan for bluetooth le devices, but I have no luck. For my device I have a mi band 6. I can connect to it from windows settings and my phone (and read it with nRF connect).

While I'm paired to the device, it can be found. I also tried this program, but still no luck.

Here's my code:

#include "mainwindow.h"
#include "ui_mainwindow.h"

QBluetoothDeviceDiscoveryAgent *discoverAgent;

QList<QBluetoothDeviceInfo> discoveredDevices;

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

    discoverAgent = new QBluetoothDeviceDiscoveryAgent(this);
    discoverAgent->setLowEnergyDiscoveryTimeout(1000);

    connect(discoverAgent, &QBluetoothDeviceDiscoveryAgent::deviceDiscovered, this, &MainWindow::addDevice);
    connect(discoverAgent, static_cast<void (QBluetoothDeviceDiscoveryAgent::*)(QBluetoothDeviceDiscoveryAgent::Error)>(&QBluetoothDeviceDiscoveryAgent::error),
            this, &MainWindow::scanError);
    connect(discoverAgent, &QBluetoothDeviceDiscoveryAgent::finished, this, &MainWindow::scanFinished);
    connect(discoverAgent, &QBluetoothDeviceDiscoveryAgent::canceled, this, &MainWindow::scanCanceled);

    discoverAgent->start();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::addDevice(const QBluetoothDeviceInfo &device)
{
    discoveredDevices.append(device);
    qDebug() << "Found BLE device" << device.name();
}

void MainWindow::scanError(QBluetoothDeviceDiscoveryAgent::Error error)
{
    qDebug() << "Failed to scan" << error;
}

void MainWindow::scanFinished()
{
    qDebug() << "scan finished";
}

void MainWindow::scanCanceled()
{
    qDebug() << "scan canceled";
}

Could it be a windows issue or is my code wrong?

[JonB]

@Sucharek
Not at all my area, but why set a discovery timeout as low as 1 second? https://doc.qt.io/qt-6/qbluetoothdevicediscoveryagent.html#setLowEnergyDiscoveryTimeout advises

For a reliable Bluetooth Low Energy discovery, use at least 40000 milliseconds.

Doubtless it won't help, but worth a try...?

But what compiler are you using under Windows? MinGW? https://stackoverflow.com/questions/61753002/invisible-ble-device-when-qt-scanning says you have to use MSVC?

[Sucharek]

Hi @JonB, so I've tried the 40 second timeout, but the scan seems to finish after 13 seconds, no matter the timeout. Even if I put -1, 200, 1000 or 40000, it's always 13 seconds.

My compiler is MinGW, but after changing it to MSVC (had to install visual basic build tools to get a working compiler), it works now! All the bluetooth devices I need have been found and the timeout works too. Thank you!
Edit: My Qt version is 5.15.2