How to detect Mindstorm EV3 using flutter_blue

Question

I am trying to setup a bluetooth server on a Mindstorm EV3 using ev3dev with python.

The server appears to work fine as it is a very basic implementation of the bluetooth server socket.

#!/usr/bin/env python3
import bluetooth
from ev3dev2.sound import Sound

sound = Sound()

server_sock = bluetooth.BluetoothSocket(bluetooth.RFCOMM)

port = 1
server_sock.bind(("", port))
server_sock.listen(1)

sound.speak("Accepting connections on port " + str(port))

client_sock, address = server_sock.accept()
sound.speak("Accepted connection from " + str(address))

data = client_sock.recv(1024)
sound.speak("received " + str(data))

client_sock.close()
server_sock.close()

The problem I am having right now is the fact that I cannot seem to detect the bluetooth signal from the EV3 in my flutter app. I can find other devices just fine and I can find the EV3 in the bluetooth settings on the phone, it's just the app that doesn't detect it.

This is the code I use to detect bluetooth devices

_btSubscription = _flutterBlue.scan().listen((scanResult) {
    if (scanResult.device.name.isEmpty || _detectedDevices.contains(scanResult.device))
        return;

        print('Found Bluetooth device: (${scanResult.device.name})');

        _detectedDevices.add(scanResult.device);

The EV3 does have a name set so it is not being ignored because of the name check.

Any advice is appreciated.

Thanks in advance

Answer 1

This is an old question, but posting this for future readers.

Note that there are many versions/variants of Bluetooth, and not all are compatible. The flutter_blue package is for BLE (Low Energy) which a recent technology, introduced in Bluetooth 4.0, and common in phones since 2015 see https://en.wikipedia.org/wiki/Bluetooth#Specifications_and_features

The Lego EV3 uses Bluetooth V2.1 EDR, (Classic Bluetooth) as do older laptops, so this will be the reason that flutterBlue.scan() does not "see" these devices. see also https://superuser.com/questions/502825/how-can-i-find-out-what-version-of-bluetooth-my-laptop-supports .

If you want to work in Flutter, with Bluetooth Classic, look at other packages like https://pub.dev/packages/flutter_bluetooth_serial . (I am not saying this will work with EV3, but at least is the right Bluetooth!)