BLE disconnect event crash

[callmeduncan]

CircuitPython version

Adafruit CircuitPython 7.3.0 on 2022-05-23; Adafruit ItsyBitsy nRF52840 Express with nRF52840

Code/REPL

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

import time

import adafruit_ble
from adafruit_ble_adafruit.adafruit_service import AdafruitServerAdvertisement
from adafruit_ble_adafruit.temperature_service import TemperatureService

# PyLint can't find BLERadio for some reason so special case it here.
ble = adafruit_ble.BLERadio()  # pylint: disable=no-member

connection = None

while True:
    print("Scanning for an Adafruit Server advertisement...")
    for adv in ble.start_scan(AdafruitServerAdvertisement, timeout=5):
        connection = ble.connect(adv)
        print("Connected")
        break

    # Stop scanning whether or not we are connected.
    ble.stop_scan()

    if connection and connection.connected:
        temp_service = connection[TemperatureService]
        while connection.connected:
            print("Temperature:", temp_service.temperature)
            time.sleep(1)

Behavior

This is the 'ble_adafruit_simpletest_client.py' from 7.x bundle, I am also running 'ble_adafruit_simpletest.py' on a second board to connect with it.
If I cause the connection to drop by rebooting / interrupting the board running 'ble_adafruit_simpletest.py' the other board running 'ble_adafruit_simpletest_client.py' locks up.
REPL can no-longer be accessed
Mass storage is still working

Description

This seems to affect all 7.x releases

On 6.3 it crashes in the same way if the board is powered on from cold, however if you power on, ctrl+c to the REPL, ctrl+d to resume and then disconnect the other side it doesn't crash, but it does not drop out of the while connection.connected: loop.

Additional information

https://forums.adafruit.com/viewtopic.php?f=60&t=191584&p=926989
supervisor.disable_ble_workflow() does not seem to help

[DavePutz]

Looks like CP is stuck in the

    while (!read_info.done) {
        RUN_BACKGROUND_TASKS;
    }

loop in common_hal_bleio_gattc_read(). The BLE_GAP_EVT_DISCONNECTED event is not being handled in _on_gattc_read_rsp_evt(), which means that read_info.done will never become true. I am not sure, however,
what is the right thing to do when the disconnect happens. I tested handling the disconnect and setting read_info.done
with a len of 0; but that just led to a TypeError in adafruit_ble/characteristics/float.py

[tannewt]

Could you set done and then check if disconnected after the loop? If disconnected, then throw a ConnectionError. Thanks for looking into this @DavePutz

[FoamyGuy]

I confirmed this does now raise the ConnectionError on 7.3.x branch.

I tested with a Feather Bluefruit Sense and CLUE devices both using builds made from 7.3.x branch.

Output on the device running the _client.py code is now:

Traceback (most recent call last):
  File "code.py", line 28, in <module>
  File "adafruit_ble/characteristics/float.py", line 46, in __get__
  File "adafruit_ble/characteristics/__init__.py", line 246, in __get__
  File "adafruit_ble/characteristics/__init__.py", line 142, in __get__
ConnectionError: Not connected

Code done running.

I think this issue can be closed now, but wanted to check if anyone else knew of anything else still outstanding?

[callmeduncan]

Thanks for sorting this!
Only thing that might still need to be done is the ble examples need updating to catch the ConnectionError condition.

[dhalbert]

Fixed by #6513 (7.3.x) and #6495 (main)