Explore what happens for native bluetooth if you have an open link hex on the device

[microbit-matt-hillsdon]

Even in BT mode I think the PF service will be open, but the V2 secure DFU service will not be. So on iOS I observed that we don't pair when we expect to (start notifications on partial flashing) and DFU fails to do so.

What about V1?

Does microbit-foundation/nordic-dfu#4 help at all?

[martinwork]

All services and characteristics in both application and Bluetooth modes should have the same security.

I think a "no pairing required" MakeCode project, with "security_level": null in pxt.json does not build correctly, but replacing null with "SECURITY_MODE_ENCRYPTION_OPEN_LINK" via Edit Settings As Text works.

microbit-foundation/codal-microbit-nrf5sdk#13
lancaster-university/codal-microbit-v2#257

[microbit-matt-hillsdon]

Thanks @martinwork. I'll pick this one up later. After our discussion it did turn out that my "just works" hex was indeed not actually just works (tested via Android nrf Connect app) so thanks for pointing out that possibility.

Once I poked MakeCode enough to get a "just works" version I got the typical CreateAI flow working. But I'll need to come back to flashing on top of an open link hex. Using the hex I had before, I do think I observed PF not require pairing and secure DFU requiring it (again tested via nrf Connect app).

[martinwork]

I do think I observed PF not require pairing and secure DFU requiring it (again tested via nrf Connect app).

That sounds right: the Bluetooth mode bits are open but the DFU mode ones aren't.