(BLE) Ability to remove default GATT services by code

[orklann]

Currently, I make a custom GATT services, and It just works only by removing some default GATT services in pxt.json like this:

"yotta": {
        "config": {
            "microbit-dal": {
                "bluetooth": {
                    "dfu_service": 0,
                    "event_service": 0,
                    "device_info_service": 0,
                    "security_level": "SECURITY_MODE_ENCRYPTION_NO_MITM"
                },
                "gatt_table_size": "0x700"
            }
        }
    }

In the above config, it removes dfu_service, event_service, device_info_service, it works fine. But after I publish my package, it would better with zero config for the users to just use my package. So I wonder if I can remove these 3 service in my package with code (in C++)?

[jaustin]

@orklann another option would be to leave these as compile time options but make them configurable in MakeCode in the same way that security_level is... Would that work well for you?

From a micro:bit point of view, turning these off makes it hard to guarantee that the apps will work smoothly (we currently tell people you don't need to enter 'Pairing/Bluetooth' mode to connect to your device if you have the Bluetooth package included, but this would change that)

Is this a way to save RAM, or something else?

[orklann]

@jaustin yes, it also works by making the same configuration in MakeCode.

Is this a way to save RAM, or something else?

My custom GATT service was coded in C++, and exposed to MakeCode via Typescript, actually I don't know why It does not work without turning off some default GATT services, and so it's not about saying RAM or something else.

I think I should make some notices to the users of my package to turned off some default GATT services via the configuration files in MakeCode, thanks for your suggestion.

[pelikhan]

Unfortunately most BLE options are C++ precompiler options and cannot be changed at runtime.

Note there's more discussion about controlling BLE memory at https://github.com/lancaster-university/microbit-dal/issues/390