Illegal argument in isolate message: (object is a ReceivePort) with MethodChannel

Question

I have a isolate with 2 function:

@override
  void initState() {
    super.initState();
    startDiscovery();
  }

void startDiscoveryIsolate(SendPort sendPort) async {
    Timer.periodic(const Duration(seconds: 1), (Timer t) async {
      await badgeSDK.startDiscovery(); //methodChannel
      CustomBLEDevice? device = await badgeSDK.getBestDevice(); //methodChannel
      if (device != null) {
        sendPort.send(device);
      }
    });
  }

  Future<void> startDiscovery() async {
    final receivePort = RawReceivePort();
    final sendPort = receivePort.sendPort;
    final isolate = await Isolate.spawn(startDiscoveryIsolate, sendPort);
    receivePort.handler = (message) {
      setState(() {
        bestGetDeviceName = message.name;
      });
    };
  }

I need to execute this functions every seconds for scanning bluetooth.

At this row:

final isolate = await Isolate.spawn(startDiscoveryIsolate, sendPort);

I have this error:

Exception has occurred. ArgumentError (Invalid argument(s): Illegal argument in isolate message: (object is a ReceivePort))

Someone can help me?