How do I (simply) do a non-connectable advert on nRF52 using SDK 15?

[Michael McClary at CloudLeaf]

I am porting a peripheral project from nRF51822 on SDK 11 to nRF52832 on SDK 15.  Currently I'm using15.0, with S132 6.0.0.  I used the template project for an initial pattern for working with SDK 15.

One thing it needs to do is (if I have the term right): "Peripheral Advertiser", i.e.

• When unconnected it advertises normally, as a connectable peripheral.
• While connected it advertises as unconnectable (so other centrals can still SEE it), but otherwise identically.
• When the connection is ended, it reverts to the connectable advertisement.

I am having difficulty finding any simple explanation for how to do this.

• Nearly everything I found was for earlier SDKs - but advertising changed massively between 14 and 15.
  • Under 15 it seems to have switched to advertising structures managed by the soft device in the latter's storage,
  • addressed by a handle/index rather than a pointer
  • not to be modified on-the-fly, but replaced by a new one (and the old one unavailable for reuse until the soft device has finished some post processing on it)
  • The automatic turn-on of advertising on connection drop (on_disconnected()) sets the type to BLE_ADV_MODE_DIRECTED_HIGH_DUTY, rather than, say,
• The closest I did find on SDK 15 was https://devzone.nordicsemi.com/f/nordic-q-a/32824/dynamically-updating-advertising-data-in-sdk-15/126346#126346,
  • That seems to be an in-process debug of a rotating-triple-buffer scheme that is also supporting on-the-fly modification of the contents of the advertisement in other ways.
  • It also seems to involve replacing components/ble/ble_advertising/* with a roll-your-own substitute.

Can someone give me (or give me a pointer to) a simple (or as simple as practical under SDK 15) scheme for just doing the basic keep-advertising-while-connected, switch-between-connectable-and-unconnectable function.

============

(I WILL be needing on-the-fly adjustment of the manufacturing field in another month or so, so info on that would also be nice.  But I need the above right away.)

Thanks.

[Vidar Berg]

Hi,

We made some major API changes to the scanner and advertising API to support the new BT 5 features. I was planning to make a simple example based on the template project in SDK 15.0.0 Today but ran out of time. I hope I can get it done Tomorrow. 

[Michael McClary at CloudLeaf]

"We made some major API changes to the scanner and advertising API..."

I see that.

I notice that, after disconnect, ble_advertising.c seems to spend some time doing directed advertising to the previous central, first fast, then slow, before opening up to others.  (I haven't checked to see whether it then shuts down after another timeout.)  I take it this is to give the previously connected central a crack at reestablishing the connection if the disconnect was unintentional.

That could be problematic, if other centrals don't "see" directed advertising.  The idea here (and the reason we want the nonconnectable advert while the peripheral is connected) is that the other centrals should be able to detect the presence of the peripheral, even if they don't want to connect to it.  Right now, when the peripheral is connected to one central (and perhaps for a while after the disconnect) the peripheral "disappears" to the others.  If ble_advertising.c does behave as described, even if the unconnectable advertisement makes it stay visible while connected, it might still disappear for a while afterward, while the previously connected central gets its exclusive opportunity to reconnect.

[awneil]

v15.3.0

[awneil]

awneil said:

With nRF Connect on Android, I can still see advertising when it's connected to another device - but there is nothing to indicate that it's non-connectable advertising

With nRF Connect Desktop v2.6.2 on Windows I see:

"Fast Advertising":

Address type: RandomStatic
Advertising type: Connectable undirected
Services: Device Information
Flags: LeGeneralDiscMode
BrEdrNotSupported
LeOnlyLimitedDiscMode
LeOnlyGeneralDiscMode
Appearance:00-00

"Non-connectable advertising":

Address type: RandomStatic
Advertising type: Scannable undirected
Services: Device Information
Flags: LeGeneralDiscMode
BrEdrNotSupported
LeOnlyLimitedDiscMode
LeOnlyGeneralDiscMode
Appearance:00-00

So does the fact that it just says "Scannable" - mean that it is non-connectable?

awneil said:

if I press the 'Connect' button, nRF Connect will try to connect

Same on Desktop!

[awneil]

Vidar Berg said:

It appears to be an Android limitation

'#~$£%%~##@@  !!

  

But the article goes on to say:

"The problem is on devices prior to Anroid 8.0"

My phone is Android 8.0 - and I still don't see it.

[awneil]

awneil said:

does the fact that it just says "Scannable" - mean that it is non-connectable?

Aparently so:

If I change

adv_params.properties.type = BLE_GAP_ADV_TYPE_NONCONNECTABLE_SCANNABLE_UNDIRECTED;

to

adv_params.properties.type = BLE_GAP_ADV_TYPE_NONCONNECTABLE_NONSCANNABLE_UNDIRECTED;

Then nRF Connect Desktop does, indeed, say:

Address type: RandomStatic

Advertising type: Non connectable undirected

Services: Device Information

Flags: LeGeneralDiscMode 

BrEdrNotSupported 

LeOnlyLimitedDiscMode

LeOnlyGeneralDiscMode

Appearance:00-00

But it will still try to connect!

[awneil]

On Android 8.0, there is no 'Connect' button for the Non-Scannable, Non-Connectable advertising.

On Android 6, the 'Connect' button is always there - Scannable on Non-scannable.

So it looks like there is a flaw in nRF Connect, too.

[awneil]

awneil said:

On Android 8.0, there is no 'Connect' button for the Non-Scannable, Non-Connectable advertising

Actually, that's not quite true.

It seems that nRF Connect is just not very good at keeping that button in-sync with the type of advertising!