pc_ble_driver_py.exceptions.NordicSemiException: Characteristic value handler not found

RE: pc_ble_driver_py.exceptions.NordicSemiException: Characteristic value handler not found

Karl Ylvisaker — Mon, 11 Jul 2022 12:35:52 GMT

Hello again, Marc

Ah, yes, it should indeed be Value Handle, not Handler* you are right.
Thank you for sharing the fix to your issue - I am glad to see that it is now resolved! :)

Please do not hesitate to open another ticket if you should encounter any other issues or questions in the future.

Good luck with your development!

Best regards,
Karl

RE: pc_ble_driver_py.exceptions.NordicSemiException: Characteristic value handler not found

marto — Mon, 11 Jul 2022 11:54:09 GMT

In fact, the error message tricked me. It should probably be `value handle` and not `value handler`.

After realizing that value_handle could be specified and debugging the search for handles, I realized that I had to specify that my UUID is vendor specific.

The fix:

from pc_ble_driver_py.ble_driver import driver

[…]

UUIDS = {
    'base': "0000XXXX-1212-EFDE-1523-785FEABCD123",
    'led': 0x1525,
    'button': 0x1524,
}

def uuid(key):
    """Parse a string and returns a BLEUUID"""
    string = UUIDS[key]
    return list(bytearray.fromhex(string.replace('-', '').replace('X', '0')))


def build_uuid(key):
    """Build a nordic BLEUUID from a key (led, button)"""
    return BLEUUID(UUIDS[key], BLEUUIDBase(uuid('base'), uuid_type=driver.BLE_UUID_TYPE_VENDOR_BEGIN))

What's strange is that googling for BLE_UUID_TYPE_VENDOR_BEGIN + python does not give a lot of answer.

Marc.

RE: pc_ble_driver_py.exceptions.NordicSemiException: Characteristic value handler not found

Karl Ylvisaker — Mon, 11 Jul 2022 11:51:16 GMT

Hello Marc,

[quote user=""]I do not know how to install a value handler and could not find documentation about it.[/quote]

Yes, unfortunately the documentation for the pc-ble-driver-py is very sparse. Fortunately, both it and the the pc-ble-driver are very similar, since they both just expose the serial interface to the connectivity device, so a lot of the time it can be helpful to take a look at the usage and inline comments from the pc-ble-driver too.

[quote user=""]status, data = self.adapter.read_req(new_conn, build_uuid('button'))[/quote]

Could you show where you set the new_conn value, and the contents of the build_uuid function?

Best regards,
Karl