Add descriptors, response callback, notify for esp32 - #2

import utime
import bluetooth

bt = bluetooth.Bluetooth()
bt.active(True)
bt.advertise(1000, 'MicroPython')

# callback
def receive(char, msg):
    # echo
    characteristics[1].notify(msg)
    print(msg)

characteristics = [
    bluetooth.Characteristic(
        0xFF01,
        bluetooth.FLAG_WRITE | bluetooth.FLAG_READ,
        receive = receive
    ),
    bluetooth.Characteristic(
        0xFF02,
        bluetooth.FLAG_NOTIFY,
        descriptors = [
            bluetooth.Characteristic(bluetooth.UUID_CHAR_CLIENT_CONFIG, bluetooth.FLAG_WRITE | bluetooth.FLAG_READ)
        ]
    )
]

bt.add_service(0x00FF, characteristics)
gc.collect()

while True:
    characteristics[0].wait() # waiting new message, async
    utime.sleep_ms(100)