Some USB device properties are only accessible if the user has the
appropriate permissions. Handle libusb1 errors to graciously skip
showing details for these devices.
Subscribe command will enable notify or indicate events from the
characteristic, depending on supported characteristic properties, and
print received values to the output window.
Unsubscribe will stop notify or indicate events.
Rename find_attribute() to find_characteristic() and return a
characteristic for a set of UUIDS, a characteristic for an attribute
handle, or None.
Print read and received values has a hex string.
Add an unsubscribe implementation to gatt_client.py. Reset the CCCD bits
to 0x0000. Remove a matching subsciber, if one is provided. Otherwise
remove all subscribers for a characteristic, since no more notify or
indicates events will be comming.
authored-by: Michael Mogenson <mogenson@google.com>
Syntax is `write <attribute> <value>`. Supports a value of type string,
hexadecimal string, or integer.
Ex:
- `write 180D.2A38 hello`
- `write 180D.2A38 0xbeef`
- `write 180D.2A38 123`
Write with response method is used if supported by characteristic,
otherwise write without response.
Add a find_attribute() method to consolidate common logic of finding a
characteristic or attribute handle in `do_read()` and `do_write()`.
Tested with run_gatt_server.py example to verify sent data.
