bluetooth with "no pairing' requires extra line in pxt.json to work correctly

[thomasjball]

Now that Web Bluetooth is more prevalent, it's easy to create web apps that can connect to the micro:bit over Bluetooth without the pairing dialog. However, this does not work properly without hand editing the pxt.json.

For a good explanation, see https://cardboard.lofirobot.com/lofi-control-app-info/

To make the board discoverable over bluetooth you have to properly set PROJECT SETTINGS in MakeCode (individual for each project!)

go to (GEAR ICON) -> PROJECT SETTINGS
Set project settings sliders to NO PAIRING
Next click EDIT SETTINGS AS TEXT
scroll down to section about BLUETOOTH and add this line: “pairing_mode”: 0,

The fix here is for MakeCode to add the pairing_mode line when "No Pairing is selected".

[martinwork]

Thomas Ball (@thomasjball) I don't think adding pairing_mode:0 is a good idea. It only appears to be a fix for the problem "your board is not discoverable by the app", and breaks the hex for mobile app use.

The problem is demonstrated in the video at around 4:00: no pairing required is selected, but the micro:bit still is not discoverable.

The bug is that MakeCode fails to use the updated no pairing required settings for the next build.
microsoft/pxt-microbit#5996

The simplest workaround is to set the pairing mode and other settings in a new project, before adding any extension or code. Then MakeCode seems to use the correct settings.

It's a caching bug - the "bad" project might well work on a different computer. Often, switching back to just works will start using the no pairing required settings, and vice versa

I think pairing_mode:0 appears to fix the problem because it triggers MakeCode to update its build settings, not that pairing_mode:0 affects discoverability. The setting for that is whitelist.

With pairing_mode:0, the micro:bit becomes unusable with the mobile apps, because it can't display the Bluetooth mode pattern for identification.

I did not find any description for the other problem mentioned: "your board crashes ofter connecting"

By the way., I noticed that the line"security_level": null is missing in the screenshot below the video

It might be good to change the default no pairing required setting to

"security_level": "SECURITY_MODE_ENCRYPTION_OPEN_LINK"

because null triggers a CODAL bug
lancaster-university/codal-microbit-v2#257

This project should work with the lofirobot website, and the mobile apps
https://makecode.microbit.org/_FX58fyCRrAMV