[aioble] After timeout, reconnection is successful. (Peripherals are always powered off)

Start with aioble/central.py:_connect and review the related state handling in aioble/device.py and aioble/client.py. Reproduce on the Raspberry Pi Pico W using the provided script with the peripheral powered off, then retry the connection. Done means a timeout leaves no false connected state and the retry does not proceed as connected or fail during service discovery.

The other device is powered off. However, after a connection timeout, it appears to be connected when retried. In fact, it is failing.

I'm not a native speaker, so sorry if my writing is wrong.

• Environment

  • Raspberry Pi Pico W with RP2040
  • MicroPython v1.24.0 on 2024-10-25
  • IDE:Thonny

• Steps to reproduce

  1. Power off the peripheral device.
  2. Timeout occurs when trying to connect.
  3. Retry and the connection succeeds. (It actually fails.)

• Code used for testing

from micropython import const
import asyncio
import aioble
# import test_aioble as aioble

import sys


_TARGET_DEVICE_ADDR = const("d7:de:4c:f4:56:e5")


async def gather(ai):
    ret=[]
    async for x in ai: ret.append(x)
    return ret


async def device_details(connection):

    if connection is None:
        return

    try:
        services = await gather(connection.services())
    except asyncio.TimeoutError as e:
        print("Timeout. (discovering services)")
        sys.print_exception(e)
    except Exception as e:
        print("Error (discovering services): {}".format(e))
        sys.print_exception(e)
    else:
        if services is None or len(services) <= 0:
            print("\n\"Service\" not found.")
            return
        
        for s in services:
            print("\t", s)


async def print_details(device):

    connection = None

    # connecting to device
    try:
        print("\nConnecting to {} ... ".format(device), end="")
        connection = await device.connect(timeout_ms=2000)
    except asyncio.TimeoutError as e:
        print("Timeout.")
        sys.print_exception(e)
    except Exception as e:
        print("Error: {}".format(e))
        sys.print_exception(e)
    else:
        print("Connected.")
        await device_details(connection)
        await connection.disconnect()


async def main():

    device = aioble.Device(aioble.ADDR_RANDOM, _TARGET_DEVICE_ADDR)

    while True:
        await print_details(device)
        r = input("\nenter return (to retry) / q(uit). > ").strip()
        if r.upper() == "Q":
            sys.exit(0)


asyncio.run(main())

• Output

MPY: soft reboot
MicroPython v1.24.0 on 2024-10-25; Raspberry Pi Pico W with RP2040

Type "help()" for more information.

>>> 

>>> %Run -c $EDITOR_CONTENT

MPY: soft reboot

Connecting to Device(ADDR_RANDOM, d7:de:4c:f4:56:e5) ... Timeout.
Traceback (most recent call last):
  File "<stdin>", line 47, in print_details
  File "aioble/device.py", line 149, in connect
  File "aioble/central.py", line 140, in _connect
  File "aioble/device.py", line 94, in __exit__
TimeoutError: 

enter return (to retry) / q(uit). > 

Connecting to Device(ADDR_RANDOM, d7:de:4c:f4:56:e5, CONNECTED) ... Connected.
Error (discovering services): can't convert NoneType to int
Traceback (most recent call last):
  File "<stdin>", line 24, in device_details
  File "<stdin>", line 14, in gather
  File "aioble/client.py", line 128, in __anext__
  File "aioble/client.py", line 120, in _start
  File "aioble/client.py", line 193, in _start_discovery
TypeError: can't convert NoneType to int

enter return (to retry) / q(uit). > 

• How to fix it
  I added exception handling because of the following problem. (It is not a good idea to fix it in this place.)
  • When the timeout occurs, the variable "_connection" in aioble is not in the correct state.
  • When the timeout occurs, the internal state of the module "bluetooth" seems to remain connected.

# https://github.com/micropython/micropython-lib/blob/master/micropython/bluetooth/aioble/aioble/central.py#L107

async def _connect(
    connection, timeout_ms, scan_duration_ms, min_conn_interval_us, max_conn_interval_us
):

                << Omitted >>

    try:
        with DeviceTimeout(None, timeout_ms):
            ble.gap_connect(
                device.addr_type,
                device.addr,
                scan_duration_ms,
                min_conn_interval_us,
                max_conn_interval_us,
            )

            # Wait for the connected IRQ.
            await connection._event.wait()
            assert connection._conn_handle is not None

            # Register connection handle -> device.
            DeviceConnection._connected[connection._conn_handle] = connection
    except:
        device._connection = None
        ble.gap_connect(None)
        raise
    finally:
        # After timeout, don't hold a reference and ignore future events.
        _connecting.remove(device)