WIPY 3.0 can't read device NOTIFY characteristic

[LukeHally]

Hi Everyone. Thanks in advance to any help you can give me.

I just received my Wipy 3.0 and Track last Friday. I watched some videos Saturday morning and got lat long and modified the class to give me atomic clock time within a couple of hours, awesome! Connected to a BLE device and read out the services and characteristics in an hour, great!

I’ve got stuck though, trying to read the value of a notify property. I can detect that the property exists and get it’s UUID, properties, instance. But can’t read the actual value of the data. I can connect with a BLE scanner on my phone and with an arduino+HM10 and read the value so know the device is working.

It is giving me this error: OSError: the requested operation failed

A google hasn't turned up much. Is it possible to read notify and indicate properties with the Wipy?

Here is my code, slightly modified from the Pycom repo:

from network import Bluetooth
import binascii
import time
bt = Bluetooth()
bt.stop_scan()
bt.start_scan(-1)

while True:
    adv = bt.get_adv()
    if adv:
        mfg_data = bt.resolve_adv_data(adv.data, Bluetooth.ADV_MANUFACTURER_DATA)

        if bt.resolve_adv_data(adv.data, Bluetooth.ADV_NAME_CMPL) == 'earconnect':
            print('connected to: {}'.format(bt.resolve_adv_data(adv.data, Bluetooth.ADV_NAME_CMPL)))
            conn = bt.connect(adv.mac)
            services = conn.services()
            for service in services:
                time.sleep(0.050)
                if type(service.uuid()) == bytes:
                    print('Reading bytes from service: {}'.format(service.uuid()))
                else:
                    print('Reading chars from service: %x' % service.uuid())
                chars = service.characteristics()
                for char in chars:
                    #if ((char.properties()) & (Bluetooth.PROP_READ or Bluetooth.PROP_INDICATE or Bluetooth.PROP_NOTIFY)):
                    if ((char.properties()) & (Bluetooth.PROP_NOTIFY)):
                        #below returns the expected uuid
                        print('char uuid: {}'.format(char.uuid()))
                        print('char instance: {}'.format(char.instance()))
                        print('char properties: {}'.format(char.properties()))
                        #line below fails with error: OSError: the requested operation failed
                        print('char read: {}'.format(char.read()))
            conn.disconnect()
            break
    else:
        #print('ADV does not exist')
        time.sleep(0.050)

[LukeHally]

In case someone else comes along looking for a solution to this problem. Simply add this callback before the while loop:

def char_notify_callback(char):
    char_value = (char.value())
    print("Got new char: {} value: {}".format(char.uuid(), char_value))

And update the char condition:

if ((char.properties()) & (Bluetooth.PROP_NOTIFY)):
                        characteristic.callback(trigger=Bluetooth.CHAR_NOTIFY_EVENT,
                                                handler=char_notify_callback,
                                                arg=None)