aioble: Connecting to the Apple Media Service (Pico-W)

Hi,

I'm trying to use a Pi Pico W to connect to the Apple Media Service, but I'm running into a few issues.

async def connectBLE():
    connection = await aioble.advertise(
        _ADV_INTERVAL_MS,
        name="AMS",
        services=[_AMS_UUID],
        appearance=0,
        manufacturer=(0xABCD, b"1234"),
    )
    print("Connection from", connection.device)
    return connection

_AMS_UUID = bluetooth.UUID("89D3502B-0F36-433A-8EF4-C502AD55F8DC")
_AMS_ENTITY_UPDATE = bluetooth.UUID("2F7CABCE-808D-411F-9A0C-BB92BA96C102")
_ADV_INTERVAL_MS = const(250000)

async def main():
    ams_service = aioble.Service(_AMS_UUID)
    aioble.register_services(ams_service)

    connection = await connectBLE()
    ams_service = await connection.service(_AMS_UUID)
    ams_entity_update_characteristic = await ams_service.characteristic(
        _AMS_ENTITY_UPDATE
    )
    await ams_entity_update_characteristic.subscribe(notify=True)

This'll connect, find the services, characteristics but then throws:

Traceback (most recent call last):
  File "<stdin>", line 160, in <module>
  File "uasyncio/core.py", line 1, in run
  File "uasyncio/core.py", line 1, in run_until_complete
  File "uasyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 139, in main
  File "aioble/client.py", line 430, in subscribe
  File "aioble/client.py", line 295, in write
GattError: 5

On the .subscribe(notify=True) bit, not sure how / if I can look up the GattError: 5 bit for more info?

There is a CircuitPython implementation here, https://docs.circuitpython.org/projects/ble_apple_media/en/latest/index.html

Which uses a "Service Solicitation" advertisement - what's the method for constructing that in aioble? I'm guessing custom adv_data & resp_data but I'm unsure of the format, etc.

That implementation also pairs to the connecting device, but when I insert a await connection.pair() I get

Traceback (most recent call last):
  File "<stdin>", line 161, in <module>
  File "uasyncio/core.py", line 1, in run
  File "uasyncio/core.py", line 1, in run_until_complete
  File "uasyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 124, in main
  File "<stdin>", line 99, in connectBLE
  File "aioble/device.py", line 256, in pair
  File "aioble/security.py", line 171, in pair
ValueError: unknown config param

Which I guess is due to the Pico-W implementation not (currently?) supporting something in ble.config(bond=bond, le_secure=le_secure, mitm=mitm, io=io)

Thanks

Start with aioble/client.py around subscribe() and write(), then inspect aioble/device.py and aioble/security.py around pair() and the BLE configuration parameters. Compare those paths with the linked CircuitPython Apple Media Service implementation and the Pico-W BLE capabilities. Done means the supported advertising, subscription, and pairing requirements are established, with any necessary aioble changes clearly scoped.