microphone gain control added to app

lib/open_earable_flutter.dart

@@ -60,6 +60,7 @@ export 'src/models/capabilities/jingle_player.dart';
 export 'src/models/capabilities/audio_player_controls.dart';
 export 'src/models/capabilities/storage_path_audio_player.dart';
 export 'src/models/capabilities/audio_mode_manager.dart';
+export 'src/models/capabilities/microphone_gain_manager.dart';
 export 'src/models/capabilities/microphone_manager.dart';
 export 'src/models/capabilities/power_saving_mode_manager.dart';
 export 'src/models/capabilities/stereo_device.dart';

lib/src/models/capabilities/microphone_gain_manager.dart

@@ -0,0 +1,70 @@
+abstract class MicrophoneGainManager {
+  Future<MicrophoneGain> getMicrophoneGain();
+
+  Future<void> setMicrophoneGain(MicrophoneGain gain);
+}
+
+class MicrophoneGain {
+  static const int maxGainRegister = 0x00;
+  static const int zeroDbRegister = 0x40;
+  static const int minGainRegister = 0xFE;
+  static const int muteRegister = 0xFF;
+  static const int defaultRegister = 0x20;
+  static const double stepDb = 0.375;
+  static const double maxGainDb = 24.0;
+  static const double minGainDb = -71.25;
+
+  final int leftRegister;
+  final int rightRegister;
+
+  const MicrophoneGain({
+    required this.leftRegister,
+    required this.rightRegister,
+  })  : assert(leftRegister >= 0 && leftRegister <= muteRegister),
+        assert(rightRegister >= 0 && rightRegister <= muteRegister);
+
+  const MicrophoneGain.stereo(int register)
+      : this(leftRegister: register, rightRegister: register);
+
+  const MicrophoneGain.muted()
+      : this.stereo(muteRegister);
+
+  bool get isMuted =>
+      leftRegister == muteRegister && rightRegister == muteRegister;
+
+  double? get leftDb => registerToDb(leftRegister);
+
+  double? get rightDb => registerToDb(rightRegister);
+
+  MicrophoneGain copyWith({
+    int? leftRegister,
+    int? rightRegister,
+  }) {
+    return MicrophoneGain(
+      leftRegister: leftRegister ?? this.leftRegister,
+      rightRegister: rightRegister ?? this.rightRegister,
+    );
+  }
+
+  static double? registerToDb(int register) {
+    _validateRegister(register);
+    if (register == muteRegister) {
+      return null;
+    }
+    return maxGainDb - (register * stepDb);
+  }
+
+  static int dbToRegister(double db) {
+    final clampedDb = db.clamp(minGainDb, maxGainDb).toDouble();
+    return ((maxGainDb - clampedDb) / stepDb)
+        .round()
+        .clamp(maxGainRegister, minGainRegister)
+        .toInt();
+  }
+
+  static void _validateRegister(int register) {
+    if (register < 0 || register > muteRegister) {
+      throw RangeError.range(register, 0, muteRegister, 'register');
+    }
+  }
+}

lib/src/models/devices/open_earable_v2.dart

@@ -33,6 +33,8 @@ const String _micSelectCharacteristicUuid =
     "0x1410df97-5f68-4ebb-a7c7-5e0fb9ae7557";
 const String _audioModeCharacteristicUuid =
     "0x1410df96-5f68-4ebb-a7c7-5e0fb9ae7557";
+const String _dmicGainCharacteristicUuid =
+    "1410df99-5f68-4ebb-a7c7-5e0fb9ae7557";
 
 const String _buttonServiceUuid = "29c10bdc-4773-11ee-be56-0242ac120002";
 const String _buttonCharacteristicUuid = "29c10f38-4773-11ee-be56-0242ac120002";
@@ -76,6 +78,7 @@ class OpenEarableV2 extends BluetoothWearable
         DeviceFirmwareVersion,
         DeviceHardwareVersion,
         MicrophoneManager<OpenEarableV2Mic>,
+        MicrophoneGainManager,
         AudioModeManager,
         EdgeRecorderManager,
         ButtonManager,
@@ -460,6 +463,38 @@ class OpenEarableV2 extends BluetoothWearable
     return availableMicrophones.firstWhere((mic) => mic.id == microphoneId);
   }
 
+  // MARK: MicrophoneGainManager
+
+  @override
+  Future<MicrophoneGain> getMicrophoneGain() async {
+    final gainBytes = await bleManager.read(
+      deviceId: deviceId,
+      serviceId: _audioConfigServiceUuid,
+      characteristicId: _dmicGainCharacteristicUuid,
+    );
+
+    if (gainBytes.length != 2) {
+      throw StateError(
+        'Microphone gain characteristic expected 2 values, but got ${gainBytes.length}',
+      );
+    }
+
+    return MicrophoneGain(
+      leftRegister: gainBytes[0],
+      rightRegister: gainBytes[1],
+    );
+  }
+
+  @override
+  Future<void> setMicrophoneGain(MicrophoneGain gain) {
+    return bleManager.write(
+      deviceId: deviceId,
+      serviceId: _audioConfigServiceUuid,
+      characteristicId: _dmicGainCharacteristicUuid,
+      byteData: [gain.leftRegister, gain.rightRegister],
+    );
+  }
+
   // MARK: AudioModeManager
 
   @override