WMI = Windows Management Interface.

The primary goal of the project is to get battery level of WH-1000XM4 headphones. Perhaps Xm4Battery might also works with similar models of headphones such as WH-1000XM3, WF-1000XM3 or WF-1000XM4.

• Xm4Battery Application
  • User Interface
  • Tray Icon Mods
• Xm4Poller
  • Start-Stop Polling
  • Connection Changed
  • Battery Level Changed
• Xm4Entity
  • Create XM4 Instance
  • Is Connected or Not?
  • What Is The Last Connected Time?
  • Headphones Battery Level
  • Re/Connect Already Paired
• PnpEntity
  • How To Find PNP Device?
  • Get / Update Specific Device Property
  • Enumerate Device Properties
  • Enable-Disable Device
• Device Specific Properties
• XM4 Related Properties
• Windows Radio
• References

The Windows Forms, trayiconed and window-less application at once.
Ready to run app is available under the Latest Release section.

System requirements: Windows 10 x64, .NET Desktop Runtime 6.0.

• F - 100% or fully charged
• 9..4 - 90..40%
• 3 yellow - 30%
• 2 orange - 20%
• 1 red - 10%
• X - headphones disconnected, gray background. Tooltip shows the last known battery level and the last connected date/time.

Right Mouse Button opens a context menu:

• Connect - tries connect already paired headphones. ⚠
• Disconnect - tries disconnect headphones (not unpair, just disconnect). ⚠
• About - leads to this page.
• Quit - closes and unloads application at all.

⚠ Connect / Disconnect items appear if the app is run as an administrator.
⚠ These functions may cause system artefacts or unusual behavior of Volume Control, Sound Mixer, Bluetooth Device Manager, etc.
⚠ Especially the Disconnect item. Connect is a law-abiding one.

Background color is defined in the CreateIconForLevel method:

var brush =
    level switch {
        > 0 and <= 10 => Brushes.Red,
        > 0 and <= 20 => Brushes.Orange,
        > 0 and <= 30 => Brushes.Yellow,
        <= 0 => Brushes.Gray,
        _ => Brushes.White
    };

Font for notification icon text (battery level or headphones status):

static readonly Font _notifyIconFont
    = new ( "Segoe UI", 16, FontStyle.Regular );

Automatically updates status of headphones.

var xm4result = Xm4Entity.Create();
if ( xm4result.IsFailed ) return 1;

Xm4Entity xm4 = xm4result.Value;

Xm4Poller statePoll = new ( xm4 );
statePoll.ConnectionChanged += Xm4state_ConnectionChanged;
statePoll.BatteryLevelChanged += Xm4state_BatteryLevelChanged;
statePoll.Start();

// starts main loop of window-less WinForms app
Application.Run();

// application was closed, quit
statePoll.Stop();

private static void Xm4state_ConnectionChanged(
    object? sender,
    bool connected )
{
    var xm4 = sender as Xm4Entity;
    ...

private static void Xm4state_BatteryLevelChanged
    object? sender,
    int batteryLevel )
{
    var xm4 = sender as Xm4Entity;
    ...

var xm4result = Xm4Entity.Create();
if ( xm4result.IsFailed ) return; // headphones did not found at all

Xm4Entity _xm4 = xm4result.Value;

...
bool connected = _xm4.IsConnected;

We don't know how to get the last connected time if headphones is online and already connected. This property is valid only if headphones are DISconnected.

Result<DateTime> dt = _xm4.LastConnectedTime;

bool disconnected = !_xm4.IsConnected;
if ( disconnected )
    Console.WriteLine( $"Last connected time: {_xm4.LastConnectedTime.Value}.\n" );
else
    var it_is_true = _xm4.LastConnectedTime.IsFailed; // can not get the last connected time

It can get the actual battery level if headphones are connected. Otherwise, headphones are DISconnected, it returns the last known level.

int level = _xm4.BatteryLevel;

When headphones are used with multiple sources (laptop, pc, smartphone, etc) you have to reconnect headphones from time to time. So headphones are already paired but disconnected. In this case WmiPnp has experimental Xm4Entity.TryConnect() and very unstable Xm4Entity.TryDisconnect(). Both want the application run as administrator. Otherwise these functions are ignored.

If you are curious to find out about turn off bluetooth at all, see topic about Windows Radio.

First, we should know a name or device id of the device we are working with or at least a part of the device name.

• ByFriendlyName - exact a friendly name.
• ByDeviceId - exact a device id, like {GUID} pid.
• LikeFriendlyName - a part of a friendly name. Returns a list of founded devices IEnumerable<PnpEntity> or empty list otherwise.
• EntityOrNone - a where part of WQL request to retrieve exact a single device only.
• EntitiesOrNone - a where part of WQL request to retrieve zero, one or several devices at once.

All of methods produce instances of PnpEntity or Result.Fail if the given device was not found.

Result<PnpEntity> result =
    PnpEntity.ByFriendlyName( "The Bluetooth Device #42" );

if ( result.IsSuccess ) { // device found
    PnpEntity btDevice = result.Value;
    ...
}

...
PnpEntity btDevice = result.Value;

Result<DeviceProperty> propertyResult =
    btDevice.GetDeviceProperty( PnpEntity.DeviceProperty_IsConnected );

if ( propertyResult.IsSuccess ) {
    DeviceProperty dp = propertyResult.Value;

    while ( !Console.KeyAvailable ) {
        bool connected = (bool)(dp.Data ?? false);

        Console.WriteLine(
            $"{btDevice.Name} is {(connected ? "connected" : "disconnected")}" );

        btDevice.UpdateProperty( dp );
    }    
}

...
PnpEntity btDevice = result.Value;

IEnumerable<DeviceProperty> properties = btDevice.UpdateProperties();

foreach( var p in properties ) {
    Console.WriteLine( $"{p.KeyName}: {p.Data}" );
    ...
}

Same thing but with a cached list of the last updated properties

_ = btDevice.UpdateProperties();

foreach( var p in btDevice.Properties ) {
    ...

Some devices could be enabled or disabled.

...
PnpEntity btDevice = result.Value;

btDevice.Disable();
btDevice.Enable();

Key = {GUID} pid

• Key = {104EA319-6EE2-4701-BD47-8DDBF425BBE5} 2
• Type = 3 (Byte)

Data is in percents

• Key = {83DA6326-97A6-4088-9453-A1923F573B29} 15
• Type = 17 (Boolean)

Data = False → device is disconnected

• Key = {83DA6326-97A6-4088-9453-A1923F573B29} 102
• KeyName = DEVPKEY_Device_LastArrivalDate
• Type = 16 (FileTime)

Data = 20230131090906.098359+180 → 2023 Jan 31, 9:09:06 GMT+3

Key = {83da6326-97a6-4088-9453-a1923f573b29} 103

• WH-1000XM4 Hands-Free AG - exact name for PnpEntity to get a BATTERY LEVEL only.
• WH-1000XM4 - exact name for PnpEntity to get a STATE of the xm4.

Actually, the app utilize templates like W_-1000XM_ to generalize model of headphones (WH-1000XM3, WF-1000XM4, etc.)

Instead of this bit flags, we can use Is Connected property to retrieve a connection status of xm4.

• Key = {4340A6C5-93FA-4706-972C-7B648008A5A7} 2

• KeyName = DEVPKEY_Device_DevNodeStatus

• Type = 7 (Uint32)

• Connected = 25190410 (fall bit#25): value & 0x20000 == 0

• Disconnected = 58744842 (set bit#25): value & 0x20000 == 0x20000

This is only property to retrieve the last connection date-time of headphones. This property appears only when headphones are DISconnected.

• Key = {2BD67D8B-8BEB-48D5-87E0-6CDA3428040A} 11
• KeyName = DEVPKEY_Bluetooth_LastConnectedTime
• Type = 16 (FileTime)

For ex.: Data = 20230131090906.098359+180 → 2023 Jan 31, 9:09:06, GMT+3

Contains the same data as the DEVPKEY_Bluetooth_LastConnectedTime property. Same behavior.

• Key = {2BD67D8B-8BEB-48D5-87E0-6CDA3428040A} 5
• Type = 16 (FileTime)

There is a way to use UWP functions from desktop application. Just setup a TargetFramework in YourProject.csproj to use specific version of dotNet-framework-windows-only like: netX.x-windows10.0.xxxxx.x. For example:

<PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net6.0-windows10.0.17763.0</TargetFramework>
    ...

Now we can use Windows.Devices.Radios namespace:

using Windows.Devices.Radios;

⚠ Be aware, this one could switch off system bluetooth radio at all (not only enable or disable).
⚠ Use at your own risk!

public static async Task OsEnableBluetooth()
    => InternalBluetoothState( enable: true );

public static async Task OsDisableBluetooth()
    => InternalBluetoothState( enable: false );

private async Task InternalBluetoothState( bool enable )
{
    var result = await Radio.RequestAccessAsync();
    if (result != RadioAccessStatus.Allowed) return;

    var bluetooth =
        (await Radio.GetRadiosAsync())
        .FirstOrDefault(
            radio => radio.Kind == RadioKind.Bluetooth );

    await bluetooth?.SetStateAsync(
        enable ? RadioState.On
        : RadioState.Off
        );
}

We can also use Windows.Devices.Bluetooth namespace or even Windows.Devices.*** for other peripheral devices.

• Enumerating windows device. Enumerating the device using the SetupDi* API provided with WinXP. CodeProject // 17 Jun 2006
• How to get the details for each enumerated device? MSDN, Archived Forums 421-440. Visual Basic
• Query battery level for WH-1000XM4 wireless headphones. GitHub gist. PowerShell
• Enable/disable already paired bluetooth devices. StackOverflow. How to connect to a paired audio Bluetooth device using Windows UWP API? PowerShell
• Talking to robots (or other devices) using Bluetooth from a Windows Runtime app. Windows.Devices.Bluetooth.Rfcomm namespace // May 7, 2014
• My Bluetooth headset can now be switched on and off from the command line. PowerShell