BLE Questions regarding GATT and reading data

[avela011]

Hey folks. I am semi-new to this whole embedded systems thing but I'm attempting to read packets from a Bluetooth Device over GATT.

Code: Select all

def scan():
    ble = BLERadio()
    print("scanning")
    found = set()
    scan_responses = set()
    # By providing Advertisement as well we include everything, not just specific advertisements.
    for advertisement in ble.start_scan(ProvideServicesAdvertisement, Advertisement):
        addr = advertisement.address
        if advertisement.scan_response and addr not in scan_responses:
            scan_responses.add(addr)
        elif not advertisement.scan_response and addr not in found:
            found.add(addr)
        else:
            continue
        if ("GotWay" in str(advertisement.complete_name)):
            print(advertisement.complete_name)
            print()
            connection = ble._adapter.connect(addr, timeout=10 )
            print(connection)
            
            for service in connection.discover_remote_services(service_uuids_whitelist=None):
                    print(service)

                    for char in service.characteristics:
                        print(char.READ)

Here is what I have so far to try and read some data from the device. However, what I'm getting back is this:
code.py output:
scanning
GotWay_55575

<Connection>
Service(UUID(0x1800))
8
8
8
8
8
Service(UUID(0x1801))
8
Service(UUID(0x180a))
8
8
8
8
8
8
8
8
8
Service(UUID(0xffe0))
8


Any help would be appreciated to move forward. I'm just not sure why I'm receiving a bunch of 8s and nothing else as I'm having trouble finding any examples/documentation to help guide me in this process.

[tannewt]

I think the 8s are the char.READ constant.

What device are you connecting to? Generally you'll need to define a Service class for the particular service you want to connect to.

[avela011]

Hey tannewt. Thanks for the reply:
Essentially I am trying to read the basic data sent out from an Electric Unicycle. Unfortunately there are no data sheets for such a device, but the only thing I've found publicly available that does it is this repo here: https://github.com/freestyl3r/euc-dash/ ... /begode.js

However I am trying to figure out how to make sense of the js and translate it to what I'm attempting to do in Circuit Python via the Feather.

[tannewt]

CircuitPython is more declarative with its BLE API. So you'll need to create a service class with one characteristic where the UUIDs match: https://github.com/freestyl3r/euc-dash/ ... #L97-L100=

It looks like it then replies with packets of different types.

This is very similar to MIDI so that may be a good place to start: https://github.com/adafruit/Adafruit_Ci ... le_midi.py

[avela011]

Alright, thats starting to make more sense. Appreciate it!
I'll follow the lead and see where it gets me