Bluetooth LE plugin for Xamarin 
Xamarin and MvvMCross plugin for accessing the bluetooth functionality. The plugin is based on the BLE implementation of Monkey Robotics.
Important Note: With the term "vanilla" we mean the non MvvmCross/pure Xamarin version. You can use it without MvvmCross, if you download the vanilla package.
Support & Limitations
| Platform | Version | Limitations |
|---|---|---|
| Xamarin.Android | 4.3 | |
| Xamarin.iOS | 7.0 |
Installation
Vanilla
// stable
Install-Package Plugin.BLE
// or pre-release
Install-Package Plugin.BLE -Pre
MvvmCross
Install-Package MvvmCross.Plugin.BLE
// or (recommended for now until we release 1.0.0 stable)
Install-Package MvvmCross.Plugin.BLE -Pre
 
Android
Add these permissions to AndroidManifest.xml. For Marshmallow, please follow Requesting Runtime Permissions in Android Marshmallow
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />Add this line to your manifest if you want to declare that your app is available to BLE-capable devices only:
<uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>Sample app
We provide a sample Xamarin.Forms app, that is a basic bluetooth LE scanner. With this app, it's possible to
- check the ble status
- discover devices
- connect/disconnect
- discover the services
- discover the characteristics
- see characteristic details
- read/write and register for notifications of a characteristic
Have a look at the code and use it as starting point to learn about the plugin and play around with it.
Usage
Vanilla
var ble = CrossBluetoothLE.Current;
var adapter = CrossBluetoothLE.Current.Adapter;MvvmCross
The MvvmCross plugin registers IBluetoothLE and IAdapter as lazy initialized singletons. You can resolve/inject them as any other MvvmCross service. You don't have to resolve/inject both. It depends on your use case.
var ble = Mvx.Resolve<IBluetoothLE>();
var adapter = Mvx.Resolve<IAdapter>();or
MyViewModel(IBluetoothLE ble, IAdapter adapter)
{
this.ble = ble;
this.adapter = adapter;
}IBluetothLE
Get the bluetooth status
var state = ble.State;You can also listen for State changes. So you can react if the user turns on/off bluetooth on you smartphone.
ble.StateChanged += (s, e) =>
{
Debug.WriteLine($"The bluetooth state changed to {e.NewState}");
};IAdapter
Scan for devices
adapter.DeviceDiscovered += (s,a) => deviceList.Add(a.Device);
await adapter.StartScanningForDevicesAsync();Connect to device
ConnectToDeviceAync returns a Task that finishes if the device has been connected successful. Otherwise a DeviceConnectionException gets thrown.
try
{
await _adapter.ConnectToDeviceAync(device);
}
catch(DeviceConnectionException e)
{
// ... could not connect to device
}Get services
var services = await connectedDevice.GetServicesAsync();or get a specific service:
var service = await connectedDevice.GetServiceAsync(Guid.Parse("ffe0ecd2-3d16-4f8d-90de-e89e7fc396a5"));Get characteristics
var characteristics = await service.GetCharacteristicsAsync();or get a specific characteristic:
var characteristic = await service.GetCharacteristicAsync(Guid.Parse("d8de624e-140f-4a22-8594-e2216b84a5f2"));Read characteristic
var bytes = await characteristic.ReadAsync();Write characteristic
await characteristic.WriteAsync(bytes);Characteristic notifications
characteristic.ValueUpdated += (o, args) =>
{
var bytes = args.Characteristic.Value;
};
characteristic.StartUpdates();
Best practice
API
- Surround Async API calls in try-catch blocks. Most BLE calls can/will throw an exception in cetain cases, this is especiialy true for Android. We will try to update the xml doc to reflect this.
try
{
await _adapter.ConnectToDeviceAsync(device);
}
catch(DeviceConnectionException ex)
{
//specific
}
catch(Exception ex)
{
//generic
}- Avoid caching of Characteristic or Service instances between connection sessions. This includes saving a reference to them in you class etc. After a device has been disconnected all Service & Characteristic instances become invalid. Allways use GetServiceAsync and GetCharacteristicAsync to get a valid instance.
General BLE iOS, Android
- Scanning: Avoid performing ble device operations like Connect, Read, Write etc while scanning for devices. Scanning is battery-intensive.
- try to stop scanning before performint device operations
- try to stop scanning as soon as you find the desired device
- never scan on a loop, and set a time limit on your scan