UniversalBLE

universal_ble version

A cross-platform (Android/iOS/macOS/Windows/Linux/Web) Bluetooth Low Energy (BLE) plugin for Flutter.

Try it online, provided your browser supports Web Bluetooth.

Features

Usage

API Support Matrix

API Android iOS macOS Windows Linux Web
startScan/stopScan ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
connect/disconnect ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
getSystemDevices ✔️ ✔️ ✔️ ✔️ ✔️ ❌
discoverServices ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
readValue ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
writeValue ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
setNotifiable ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
pair ✔️ ✔️ ✔️ ✔️ ✔️ ⏺
unpair ✔️ ❌ ❌ ✔️ ✔️ ❌
isPaired ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
onPairingStateChange ✔️ ⏺ ⏺ ✔️ ✔️ ⏺
getBluetoothAvailabilityState ✔️ ✔️ ✔️ ✔️ ✔️ ❌
enableBluetooth ✔️ ❌ ❌ ✔️ ✔️ ❌
onAvailabilityChange ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
requestMtu ✔️ ✔️ ✔️ ✔️ ✔️ ❌

Getting Started

Add universal_ble in your pubspec.yaml:

dependencies:
  universal_ble:

and import it wherever you want to use it:

import 'package:universal_ble/universal_ble.dart';

Scanning

// Set a scan result handler
UniversalBle.onScanResult = (bleDevice) {
  // e.g. Use BleDevice ID to connect
}

// Perform a scan
UniversalBle.startScan();

// Or optionally add a scan filter
UniversalBle.startScan(
  scanFilter: ScanFilter(
    withServices: ["SERVICE_UUID"],
    withManufacturerData: ["MANUFACTURER_DATA"]
  )
);

// Stop scanning
UniversalBle.stopScan();

Before initiating a scan, ensure that Bluetooth is available:

AvailabilityState state = await UniversalBle.getBluetoothAvailabilityState();
// Start scan only if Bluetooth is powered on
if (state == AvailabilityState.poweredOn) {
  UniversalBle.startScan();
}

// Or listen to bluetooth availability changes
UniversalBle.onAvailabilityChange = (state) {
  if (state == AvailabilityState.poweredOn) {
    UniversalBle.startScan();
  }
};

See the Bluetooth Availability section for more.

System Devices

Already connected devices, connected either through previous sessions, other apps or through system settings, won't show up as scan results. You can get those using getSystemDevices().

// Get already connected devices
// You can set `withServices` to narrow down the results
// On `Apple`, `withServices` is required to get connected devices, else [1800] service will be used as default filter.
List<BleDevice> devices = await UniversalBle.getSystemDevices(withServices: []);

For each such device the isSystemDevice property will be true.

You still need to explicitly connect to them before being able to use them.

Scan Filter

You can optionally set filters when scanning.

With Services

When setting this parameter, the scan results will only include devices that advertise any of the specified services. This is the primary filter. All devices are first filtered by services, then further filtered by other criteria. This parameter is mandatory on web if you want to access those services.

List<String> withServices;
With ManufacturerData

Use the withManufacturerData parameter to filter devices by manufacturer data. When you pass a list of ManufacturerDataFilter objects to this parameter, the scan results will only include devices that contain any of the specified manufacturer data.

List<ManufacturerDataFilter> withManufacturerData;
With namePrefix

Use the withNamePrefix parameter to filter devices by names (case sensitive). When you pass a list of names, the scan results will only include devices that have this name or start with the provided parameter.

List<String> withNamePrefix;

Connecting

// Connect to a device using the `deviceId` of the BleDevice received from `UniversalBle.onScanResult`
String deviceId = bleDevice.deviceId;
UniversalBle.connect(deviceId);

// Disconnect from a device
UniversalBle.disconnect(deviceId);

// Get connection/disconnection updates
UniversalBle.onConnectionChange = (String deviceId, bool isConnected) {
  debugPrint('OnConnectionChange $deviceId, $isConnected');
}

// Get current connection state
// Can be connected, disconnected, connecting or disconnecting
BleConnectionState connectionState = await bleDevice.connectionState;

Discovering Services

After establishing a connection, you need to discover services. This method will discover all services and their characteristics.

// Discover services of a specific device
UniversalBle.discoverServices(deviceId);

Reading & Writing data

You need to first discover services before you are able to read and write to characteristics.

// Read data from a characteristic
UniversalBle.readValue(deviceId, serviceId, characteristicId);

// Write data to a characteristic
UniversalBle.writeValue(deviceId, serviceId, characteristicId, value);

// Subscribe to a characteristic
UniversalBle.setNotifiable(deviceId, serviceId, characteristicId, BleInputProperty.notification);

// Get characteristic updates in `onValueChange`
UniversalBle.onValueChange = (String deviceId, String characteristicId, Uint8List value) {
  debugPrint('onValueChange $deviceId, $characteristicId, ${hex.encode(value)}');
}

// Unsubscribe from a characteristic
UniversalBle.setNotifiable(deviceId, serviceId, characteristicId, BleInputProperty.disabled);

Pairing

// Pair
bool? isPaired = await UniversalBle.pair(deviceId); // Returns true if successful

// For Apple and Web, you can optionally pass a pairingCommand if you know an encrypted read or write characteristic.
// Not supported on Web/Windows
UniversalBle.pair(deviceId, pairingCommand: BleCommand(service:"SERVICE", characteristic:"ENCRYPTED_CHARACTERISTIC",));

// Receive pairing state changes
UniversalBle.onPairingStateChange = (String deviceId, bool isPaired) {
  // Handle pairing state change
}

// Unpair
UniversalBle.unpair(deviceId);

// Check current pairing state
bool? isPaired = UniversalBle.isPaired(deviceId);

Bluetooth Availability

// Get current Bluetooth availability state
AvailabilityState availabilityState = UniversalBle.getBluetoothAvailabilityState(); // e.g. poweredOff or poweredOn,

// Receive Bluetooth availability changes
UniversalBle.onAvailabilityChange = (state) {
  // Handle the new Bluetooth availability state
};

// Enable Bluetooth programmatically
UniversalBle.enableBluetooth();

Command Queue

By default, all commands are executed in a global queue (QueueType.global), with each command waiting for the previous one to finish.

If you want to parallelize commands between multiple devices, you can set:

// Create a separate queue for each device.
UniversalBle.queueType = QueueType.perDevice;

You can also disable the queue completely and parallelize all commands, even for the same device, by using:

// Disable queue
UniversalBle.queueType = QueueType.none;

Keep in mind that some platforms (e.g. Android) may not handle well devices that fail to process consecutive commands without a minimum interval. Therefore, it is not advised to set queueType to none.

You can get queue updates by setting:

// Get queue state updates
UniversalBle.onQueueUpdate = (String id, int remainingItems) {
  debugPrint("Queue: $id Remaining: $remainingItems");
};

Timeout

By default, all commands have a timeout of 10 seconds.

// Change timeout
UniversalBle.timeout = const Duration(seconds: 10);

// Disable timeout
UniversalBle.timeout = null;

UUID Format Agnostic

UniversalBLE is agnostic to the UUID format of services and characteristics regardless of the platform the app runs on. When passing a UUID, you can pass it in any format (long/short) or character case (upper/lower case) you want. UniversalBLE will take care of necessary conversions, across all platforms, so that you don't need to worry about underlying platform differences.

For consistency, all characteristic and service UUIDs will be returned in lowercase 128-bit format, across all platforms, e.g. 0000180a-0000-1000-8000-00805f9b34fb.

Utility Methods

If you need to convert any UUIDs in your app you can use the following methods.

  • BleUuidParser.string() converts a string to a 128-bit UUID formatted string:
BleUuidParser.string("180A"); // "0000180a-0000-1000-8000-00805f9b34fb"

BleUuidParser.string("0000180A-0000-1000-8000-00805F9B34FB"); // "0000180a-0000-1000-8000-00805f9b34fb"
  • BleUuidParser.number() converts a number to a 128-bit UUID formatted string:
BleUuidParser.number(0x180A); // "0000180a-0000-1000-8000-00805f9b34fb"
  • BleUuidParser.compare() compares two differently formatted UUIDs:
BleUuidParser.compare("180a","0000180A-0000-1000-8000-00805F9B34FB"); // true

Platform-specific Setup

Android

Add the following permissions to your AndroidManifest.xml file:

<uses-permission android:name="android.permission.BLUETOOTH_SCAN" android:usesPermissionFlags="neverForLocation" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" android:maxSdkVersion="30" />

If you use BLUETOOTH_SCAN to determine location, modify your AndroidManifest.xml file to include the following entry:

 <uses-permission android:name="android.permission.BLUETOOTH_SCAN" tools:remove="android:usesPermissionFlags" tools:targetApi="s" />

If your app uses location services, remove android:maxSdkVersion="30" from the location permission tags.

iOS / macOS

Add NSBluetoothPeripheralUsageDescription and NSBluetoothAlwaysUsageDescription to Info.plist of your iOS and macOS app.

Add the Bluetooth capability to the macOS app from Xcode.

Windows / Linux

Your Bluetooth adapter needs to support at least Bluetooth 4.0. If you have more than 1 adapters, the first one returned from the system will be picked.

When publishing on Windows you need to declare the following capabilities: bluetooth, radios.

Web

On web, the withServices parameter in the ScanFilter is used as optional_services as well as a services filter. On web you have to set this parameter to ensure that you can access the specified services after connecting to the device. You can leave it empty for the rest of the platforms if your device does not advertise services.

ScanFilter(
      withServices: kIsWeb ?  ["SERVICE_UUID"] : [],
)

Customizing Platform Implementation of UniversalBle

// Create a class that extends UniversalBlePlatform
class UniversalBleMock extends UniversalBlePlatform {
  // Implement all commands
}

UniversalBle.setInstance(UniversalBleMock());

Libraries

universal_ble