Starts a Bluetooth SPP server that forwards traffic to a locally connected serial device that uses the SkyWatcher serial protocol

readme.md

SkyWatcher Serial Protocol Bluetooth Server

Bluetooth server supporting SPP profile for relaying SkyWatcher serial protocol commands to a locally connected mount. This has been tested on a Raspberry PI 4, might work on older models/different Linux systems.

Server setup

• Create a virtual environment (venv), activate via ./venv/bin/activate
• Install required modules via requirements.txt via pip3 install -r requirements.txt (might require installing native deps)
• Open a different terminal with bluetoothctl
• Run the Python script and wait for a connection, you might have to trust it first via the open bluetoothctl session

Client setup (Windows)

• Open Bluetooth settings
• More Bluetooth Settings
• Com Ports
• Add outgoing
• Browse
• Serial Port service should appear (after trusting on the server side)
• A COM port will be assigned
• Configure COM port in Device Manager, tested with 115200 baud

TODO

Make device and baud rate configurable via command line arguments

bluetooth_serial_server_sw.py

#!/usr/bin/python3

import os
import dbus
import dbus.service
import dbus.mainloop.glib
import serial
from gi.repository import GLib


class Profile(dbus.service.Object):
    fd = -1
    ser = None

    @dbus.service.method('org.bluez.Profile1',
                         in_signature='',
                         out_signature='')
    def Release(self):
        if self.ser is not None:
            self.ser.close()
        print('Release')

    @dbus.service.method('org.bluez.Profile1',
                         in_signature='oha{sv}',
                         out_signature='')
    def NewConnection(self, path, fd, properties):
        if self.ser is None:
            self.ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
        self.fd = fd.take()
        print('NewConnection(%s, %d)' % (path, self.fd))
        for key in properties.keys():
            if key == 'Version' or key == 'Features':
                print('  %s = 0x%04x' % (key, properties[key]))
            else:
                print('  %s = %s' % (key, properties[key]))
        io_id = GLib.io_add_watch(self.fd,
                                  GLib.PRIORITY_DEFAULT,
                                  GLib.IO_IN | GLib.IO_PRI,
                                  self.io_cb)

    def io_cb(self, fd, conditions):
        ser = self.ser
        data = os.read(fd, 64)
        # print(data)
        ser.write(data)
        
        res = bytes()
        eol = False
        while not eol:
            if ser.inWaiting() > 0:
                char = ser.read()
                if char == b'\r':
                    eol = True
                res += char

        # print(res)
        os.write(fd, res)
        return True

    @dbus.service.method('org.bluez.Profile1',
                         in_signature='o',
                         out_signature='')
    def RequestDisconnection(self, path):
        print('RequestDisconnection(%s)' % (path))

        if self.fd > 0:
            os.close(self.fd)
            self.fd = -1


def main():
    dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)

    bus = dbus.SystemBus()

    manager = dbus.Interface(bus.get_object('org.bluez',
                                            '/org/bluez'),
                             'org.bluez.ProfileManager1')

    mainloop = GLib.MainLoop()

    adapter = dbus.Interface(bus.get_object('org.bluez',
                                            '/org/bluez/hci0'),
                            dbus.PROPERTIES_IFACE)
    discoverable = adapter.Get('org.bluez.Adapter1', 'Discoverable')
    if not discoverable:
        print('Making discoverable...')
        adapter.Set('org.bluez.Adapter1', 'Discoverable', True)

    profile_path = '/foo/baz/profile'
    server_uuid = '00001101-0000-1000-8000-00805f9b34fb'
    opts = {
        'Version': dbus.UInt16(0x0102),
        'AutoConnect': dbus.Boolean(True),
        'Role': 'server',
        'Name': 'SerialPort',
        'Service': '00001101-0000-1000-8000-00805f9b34fb',
        'RequireAuthentication': dbus.Boolean(False),
        'RequireAuthorization': dbus.Boolean(False),
        'Channel': dbus.UInt16(1),
    }

    print('Starting Serial Port Profile...')

    profile = Profile(bus, profile_path)

    manager.RegisterProfile(profile_path, server_uuid, opts)

    try:
        mainloop.run()
    except KeyboardInterrupt:
        mainloop.quit()


if __name__ == '__main__':
    main()

requirements.txt

bluedot==2.0.0
certifi==2023.11.17
charset-normalizer==3.3.2
dbus-python==1.3.2
future==0.18.3
idna==3.4
iso8601==2.1.0
pyserial==3.5
PyYAML==6.0.1
requests==2.31.0
urllib3==2.1.0