Add support for chipsea / OKOK 2.0 scales

[inzanity]

For now only handles weight, impedance is read, but not used for
anything, algorithms not known.

The scale does not indicate whether it is sending the weight in kg or in
lbs, always assuming kg.

Based on findings from #496

[oliexdev]

thanks for your work but could rewrite your code that you don't overwrite connect/disconnect and onDiscoveredPeripheral. You can put the logic in onNextStep and onBluetoothNotify

[inzanity]

I didn't figure out a way to get the advertisement data any other way, am I missing something?

[oliexdev]

You need to turn on the notification in onNextStep with:

        switch (stepNr) {
            case 0:
                //Tell device to send us weight measurements
                setNotificationOn(WEIGHT_MEASUREMENT_SERVICE, WEIGHT_MEASUREMENT_SERVICE);
                break;
         }

Then you will receive any weight advertisement in onBluetoothNotify.

The WEIGHT_MEASUREMENT_SERVICE and WEIGHT_MEASUREMENT_SERVICE could be different but the default values are:

    private final UUID WEIGHT_MEASUREMENT_SERVICE = BluetoothGattUuid.fromShortCode(0xfff0);
    private final UUID WEIGHT_MEASUREMENT_CHARACTERISTIC = BluetoothGattUuid.fromShortCode(0xfff1);

[inzanity]

The device is a pure broadcaster and does not advertise any GATT services (nor characteristics). All the data is simply in a manufacturer specific data field in the advertisement.

The fields present in the advertisement are:

• 02 01 04: flags = BLE_GAP_ADV_FLAG_BR_EDR_NOT_SUPPORTED
• 04 09 04 09 41 44 56: name = ADV
• 16 ff ... = 23 bytes of manufacturer specific data

As far as I understand, this data would only be received in the onDiscoveredPeripheral() callback in BluetoothCommunication.java which throws the ScanResult object away and stops receiving updates after the first received package (which contains only the very first measurement, likely quite close to zero).

Still, this is the only way I've perceived this kind of broadcaster-listener can be implemented without altering BluetoothCommunication.

[oliexdev]

that would be really strange, could you do step 2 from https://github.com/oliexdev/openScale/wiki/How-to-reverse-engineer-a-Bluetooth-4.x-scale and post the results here?

[inzanity]

openScale_2021-03-04_09-57.txt

When I click on the scale, it pops up a never ending spinner.

[oliexdev]

you are using an old version of openScale?

But if its not work please use the BLE scanner app.

[inzanity]

This is all that I got with BLE Scanner, which says the same, not connectable and 3 fields in the advertisement.

[oliexdev]

ok that would be the first scale without an Bluetooth service but if its works I will merge it. Do you have maybe a photo of the scale for out gallery (same camera angle like the other ones)? I can't use the official one due copyright reasons.

And thanks for your work. 🥇