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Low Level API

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 using stream
UniversalBle.connectionStream(deviceId).listen((bool isConnected) {
  debugPrint('Is device $deviceId connected?: $isConnected');
});

// Or set a handler to get updates of all devices
UniversalBle.onConnectionChange = (String deviceId, bool isConnected, String? error) {
  debugPrint('Is device $deviceId connected?: $isConnected. Error: $error');
}

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.read(deviceId, serviceId, characteristicId);

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

// Subscribe to a characteristic notifications
UniversalBle.subscribeNotifications(deviceId, serviceId, characteristicId);

// Subscribe to a characteristic indications
UniversalBle.subscribeIndications(deviceId, serviceId, characteristicId);

// Get characteristic notifications/indications updates using stream
UniversalBle.characteristicValueStream(deviceId, characteristicId).listen((Uint8List value) {
  debugPrint('OnValueChange $deviceId, $characteristicId, ${hex.encode(value)}');
});

// Or set a handler to get updates of all characteristics
UniversalBle.onValueChange = (String deviceId, String characteristicId, Uint8List value) {
  debugPrint('onValueChange $deviceId, $characteristicId, ${hex.encode(value)}');
}

// Unsubscribe from notifications/indications
UniversalBle.unsubscribe(deviceId, serviceId, characteristicId);

Pairing

Trigger pairing

Pair on Android, Windows, Linux
await UniversalBle.pair(deviceId);
Pair on Apple and web

For Apple and Web, pairing support depends on the device. Pairing is triggered automatically by the OS when you try to read/write from/to an encrypted characteristic.

Calling UniversalBle.pair(deviceId) will only trigger pairing if the device has an encrypted read characteristic.

If your device only has encrypted write characteristics or you happen to know which encrypted read characteristic you want to use, you can pass it with a pairingCommand.

UniversalBle.pair(deviceId, pairingCommand: BleCommand(service:"SERVICE", characteristic:"ENCRYPTED_CHARACTERISTIC"));

After pairing you can check the pairing status.

Pairing status

Pair on Android, Windows, Linux
// Check current pairing state
bool? isPaired = UniversalBle.isPaired(deviceId);
Pair on Apple and web

For Apple and Web, you have to pass a "pairingCommand" with an encrypted read or write characteristic. If you don't pass it then it will return null.

bool? isPaired = await UniversalBle.isPaired(deviceId, pairingCommand: BleCommand(service:"SERVICE", characteristic:"ENCRYPTED_CHARACTERISTIC"));
Discovering encrypted characteristic

To discover encrypted characteristics, make sure your device is not paired and use the example app to read/write to all discovered characteristics one by one. If one of them triggers pairing, that means it is encrypted and you can use it to construct BleCommand(service:"SERVICE", characteristic:"ENCRYPTED_CHARACTERISTIC").

Pairing state changes

// Get pairing state updates using stream
UniversalBle.pairingStateStream(deviceId).listen((bool paired) {
  // Handle pairing state change
});

// Or set a handler to get pairing state updates of all devices
UniversalBle.onPairingStateChange = (String deviceId, bool paired) {}

Unpair

UniversalBle.unpair(deviceId);

Request MTU

This method will attempt to set the MTU (Maximum Transmission Unit) but it is not guaranteed to succeed due to platform limitations. It will always return the current MTU.

int mtu = await UniversalBle.requestMtu(widget.deviceId, 247);

Read RSSI

Read the signal strength (RSSI) of a connected device.

int rssi = await UniversalBle.readRssi(deviceId);

⚠️ Note: The device must be connected before reading RSSI.

Platform Limitations

  • Android / iOS / macOS: Fully supported.

  • Windows / Linux / Web: Not supported.