How do I connect microbit with BLE and listen for button press events?

I think this might be an XY problem. What I have understood is that you want to send a button press from the micro:bit to the RPi via Bluetooth Low Energy (BLE). If that is the case, then there is a more efficient way to do this.

In the Bluetooth Profile for the micro:bit there is a button service and a button A status characteristic that can be used. Their UUIDs are:

BTN_SRV = 'E95D9882-251D-470A-A062-FA1922DFA9A8'
BTN_A_STATE = 'E95DDA90-251D-470A-A062-FA1922DFA9A8'

You need to set up the GATT server on the micro:bit. The most efficient way to do this is using https://makecode.microbit.org/#editor to create the following:

If you don’t have Bluetooth on the left-hand menu then click on the cog in the top right of the screen, select Extensions, and then select Bluetooth to replace the Radio extension.

The GATT client code on the RPi can be simplified by using the pydbus library for the D-Bus bindings.

With Bluetooth, rather than have a while loop and keep polling the micro:bit, it is more efficient to have an event loop that subscribes to notifications from (in this case) the Button A characteristic. The function I have named btn_handler is called each time the micro:bit button A is pressed or released.

The code below doesn’t do the initial pairing between the micro:bit and the RPi. As pairing is a one-off provisioning step I do that manually.

Here is example python code for the RPi that responses to Button A on the micro:bit being pressed…

from time import sleep
import pydbus
from gi.repository import GLib

DEVICE_ADDR = 'DE:82:35:E7:CE:BE' #  micro:bit address
BTN_A_STATE = 'E95DDA90-251D-470A-A062-FA1922DFA9A8'

# DBus object paths
BLUEZ_SERVICE = 'org.bluez'
ADAPTER_PATH = '/org/bluez/hci0'
device_path = f"{ADAPTER_PATH}/dev_{DEVICE_ADDR.replace(':', '_')}"

# setup dbus
bus = pydbus.SystemBus()
mngr = bus.get(BLUEZ_SERVICE, "https://stackoverflow.com/")
adapter = bus.get(BLUEZ_SERVICE, ADAPTER_PATH) 
device = bus.get(BLUEZ_SERVICE, device_path)

device.Connect()

while not device.ServicesResolved:
    sleep(0.5)

def get_characteristic_path(dev_path, uuid):
    """Look up DBus path for characteristic UUID"""
    mng_objs = mngr.GetManagedObjects()
    for path in mng_objs:
        chr_uuid = mng_objs[path].get('org.bluez.GattCharacteristic1', {}).get('UUID')
        if path.startswith(dev_path) and chr_uuid == uuid.casefold():
           return path

# Characteristic DBus information
btn_a_path = get_characteristic_path(device._path, BTN_A_STATE)
btn_a = bus.get(BLUEZ_SERVICE, btn_a_path)
# Read button A without event loop notifications
print(btn_a.ReadValue({}))

# Enable eventloop for notifications
def btn_handler(iface, prop_changed, prop_removed):
    """Notify event handler for button press"""
    if 'Value' in prop_changed:
        new_value = prop_changed['Value']
        print(f"Button A state: {new_value}")
        print(f'As byte: {bytes(new_value)}')
        print(f'As bytearray: {bytearray(new_value)}')
        print(f'As int: {int(new_value[0])}')
        print(f'As bool: {bool(new_value[0])}')

mainloop = GLib.MainLoop()
btn_a.onPropertiesChanged = btn_handler
btn_a.StartNotify()
try:
    mainloop.run()
except KeyboardInterrupt:
    mainloop.quit()
    btn_a.StopNotify()
    device.Disconnect()