Windows 10 蓝牙低功耗连接 c#

Question

对于一个项目，我需要使用 C# 从 Windows 10 上的蓝牙设备获取一些数据。我对蓝牙 API 不太熟悉，无法弄清楚为什么以下内容不起作用：

使用BluetoothLEAdvertisementWatcher 搜索广告，效果很好。我确实收到了来自设备的广告（本地名称适合）以及ServiceUuids。接下来我尝试使用与广告一起收到的BluetoothAddress 连接到设备：

private async void OnAdvertisementReceived(BluetoothLEAdvertisementWatcher watcher, 
                    BluetoothLEAdvertisementReceivedEventArgs eventArgs)
{
    ulong blAdress = eventArgs.BluetoothAddress;
    BluetoothLEDevice blDevice = await 
         Windows.Devices.Bluetooth.BluetoothLEDevice.FromBluetoothAddressAsync(blAdress);
}

但是，这样做会导致异常：

未找到元素。 （HRESULT 异常：0x80070490）。

这是从设备读取数据的正确方法吗？是否有其他选项可用于从服务中读取数据？在 Windows 中手动配对设备并不是一个真正的选择，而且似乎也失败了。

/Edit 1：我检查设备的本地名称以确保我只尝试连接到正确的设备。所以我猜想连接到这个特定设备有问题，但我仍然不知道如何解决这个问题。服务数据在iOS上读取成功，应该是可以的。

Answer 1

在 MS 解决这个问题之前，我发现连接到 BLE 设备的唯一可靠解决方案是向注册表询问配对 BLE 设备的列表，并将广告中的蓝牙地址与配对的注册表列表进行比较设备。我的经验是，当在未配对的设备上调用 FromBluetoothAddressAsync 时，Windows 会引发异常并终止观察者线程。我有一些我很乐意分享的 C++ 代码，它读取注册表并创建配对的 BLE 设备列表。

希望 MS 能够像 Apple 一样花时间全面支持 BLE。

Answer 2

这是来自 MS (https://social.msdn.microsoft.com/Forums/vstudio/en-US/e321cb3c-462a-4b16-b7e4-febdb3d0c7d6/windows-10-pairing-a-ble-device-from-code?forum=wdk) 的参考。似乎要使用此 BluetoothLEDevice.FromBluetoothAddressAsync，我们必须在设备正在广告但尚未配对时处理异常。

Answer 3

当我直接使用 BluetoothLEAdvertisementWatcher 时，我遇到了同样的问题。

然后我测试了观察者列出的不同地址。我发现它与蓝牙设备有关。

添加如下过滤器后，我可以成功连接到GATT设备（TI Sensor Tag）。

public sealed partial class MainPage : Page
{
    private BluetoothLEAdvertisementWatcher watcher;

    public MainPage()
    {
        this.InitializeComponent();

        // Create and initialize a new watcher instance.
        watcher = new BluetoothLEAdvertisementWatcher();

        // Part 1B: Configuring the signal strength filter for proximity scenarios

        // Configure the signal strength filter to only propagate events when in-range
        // Please adjust these values if you cannot receive any advertisement 
        // Set the in-range threshold to -70dBm. This means advertisements with RSSI >= -70dBm 
        // will start to be considered "in-range".
        watcher.SignalStrengthFilter.InRangeThresholdInDBm = -70;

        // Set the out-of-range threshold to -75dBm (give some buffer). Used in conjunction with OutOfRangeTimeout
        // to determine when an advertisement is no longer considered "in-range"
        watcher.SignalStrengthFilter.OutOfRangeThresholdInDBm = -75;

        // Set the out-of-range timeout to be 2 seconds. Used in conjunction with OutOfRangeThresholdInDBm
        // to determine when an advertisement is no longer considered "in-range"
        watcher.SignalStrengthFilter.OutOfRangeTimeout = TimeSpan.FromMilliseconds(2000);

        // By default, the sampling interval is set to zero, which means there is no sampling and all
        // the advertisement received is returned in the Received event

        // End of watcher configuration. There is no need to comment out any code beyond this point.
    }


    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        watcher.Received += OnAdvertisementReceived;

        watcher.Stopped += OnAdvertisementWatcherStopped;

        App.Current.Suspending += App_Suspending;

        App.Current.Resuming += App_Resuming;
    }


    protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
    {
        App.Current.Suspending -= App_Suspending;
        App.Current.Resuming -= App_Resuming;

        watcher.Stop();

        watcher.Received -= OnAdvertisementReceived;
        watcher.Stopped -= OnAdvertisementWatcherStopped;

        base.OnNavigatingFrom(e);
    }


    private void App_Suspending(object sender, Windows.ApplicationModel.SuspendingEventArgs e)
    {
        // Make sure to stop the watcher on suspend.
        watcher.Stop();
        // Always unregister the handlers to release the resources to prevent leaks.
        watcher.Received -= OnAdvertisementReceived;
        watcher.Stopped -= OnAdvertisementWatcherStopped;

    }

    private void App_Resuming(object sender, object e)
    {
        watcher.Received += OnAdvertisementReceived;
        watcher.Stopped += OnAdvertisementWatcherStopped;
    }

    private async void OnAdvertisementReceived(BluetoothLEAdvertisementWatcher watcher, BluetoothLEAdvertisementReceivedEventArgs eventArgs)
    {
        var address = eventArgs.BluetoothAddress;

        BluetoothLEDevice device = await BluetoothLEDevice.FromBluetoothAddressAsync(address);

        var cnt =device.GattServices.Count;

        watcher.Stop();
    }

    /// <summary>
    /// Invoked as an event handler when the watcher is stopped or aborted.
    /// </summary>
    /// <param name="watcher">Instance of watcher that triggered the event.</param>
    /// <param name="eventArgs">Event data containing information about why the watcher stopped or aborted.</param>
    private void OnAdvertisementWatcherStopped(BluetoothLEAdvertisementWatcher watcher, BluetoothLEAdvertisementWatcherStoppedEventArgs eventArgs)
    {

    }

    private void start_Click(object sender, RoutedEventArgs e)
    {
        watcher.Start();
    }
}

Answer 4

只是一个猜测，但也许你需要这个：

watcher.ScanningMode = BluetoothLEScanningMode.Active;

在 OnAdvertisementReceived 事件中

if (e.AdvertisementType == BluetoothLEAdvertisementType.ScanResponse)
{
  BluetoothLEDevice blDevice = await BluetoothLEDevice.FromBluetoothAddressAsync(e.BluetoothAddress);
}

Answer 5

如果这是一个 UWP 项目，请确保启用蓝牙功能。

为此，请在 Visual Studio 解决方案资源管理器中双击 *.appxmanifest，选择“功能”选项卡并确保选中“蓝牙”。

它会添加一些与以下类似的xml；

<Capabilities>
    <Capability Name="internetClientServer" />
    <DeviceCapability Name="bluetooth" />
</Capabilities>

Answer 6

这个问题已经超过 3 年了，但是因为它有超过 13000 的浏览量，所以我会回答。 Element not found 的原因是 Windows.Devices 在配对或连接之前不知道广告 Ble 设备。 而是在 OnAdvertisementReceived 中使用：

 var device = await BluetoothLEDevice.FromBluetoothAddressAsync(eventArgs.BluetoothAddress);

我在 github 上也有一个非常简单的 uwp 示例，它没有控制以使其尽可能简单。所有结果都显示在调试输出窗口中。 最有用的信息在 MainPage.xaml.cs 中

查看：https://github.com/GrooverFromHolland/SimpleBleExample_by_Devicename