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Re: Zephyr Low Level BLE Radio question

Chettimada, Vinayak Kariappa
 

> I still do not see any parameter where I can set my own frequency… This is the main part that I have been working on for a while now.

Does this mean I DO have to use the ll_sw files?

 

There are no standard HCI interface to set application defined radio frequency, this will be against the Bluetooth specifications.

 

Refer to Bluetooth Specification V5.2, Vol 6, Part B, section 4.4.2.1 Advertising channel index selection:

 

Advertising events use three predefined primary advertising physical channels.

Primary advertising channel indices are either used or unused.

For AUX_ADV_IND and AUX_CHAIN_IND PDUs, the secondary advertising

channel index used in the Channel Index subfield of the AuxPtr field is

implementation specific. It is recommended that sufficient channel diversity is

used to avoid collisions.

 

In the Zephyr BLE controller, advertising extensions is experimental, and the function that fills the advertising channel can be found here:

https://github.com/zephyrproject-rtos/zephyr/blob/master/subsys/bluetooth/controller/ll_sw/ull_adv_aux.c#L788

 

 

>Bit 10 telling to make use of the extended advertising (which I assume are the 255 byte payload messages). It usually sends a smaller header packet first on the primary channels that points to the actual data packet.

 

Correct.

 

>Bit 15-17 disable the advertising on the normal advertising channels. Does this mean that the previous process behaves differently? Or just skip the first ‘small header’ part?

 

These bits decide the `advertising event` on the primary channels, to use channel 37, 38, and 39. The `small header` is repeated in these channels inside a standard `advertising event`, and that is what is selected by these bits.

For further details please refer to Bluetooth specifications.

 

-Vinayak

 

From: steven ghekiere <stevenghekiere@...>
Sent: 15 December 2020 20:51
To: Chettimada, Vinayak <vinayak.kariappa.chettimada@...>; Marciano Preciado <marciano@...>
Cc: users@...
Subject: RE: [Zephyr-users] Zephyr Low Level BLE Radio question

 

 

Hey Vinayak,

 

Thanks for the reply!

 

I had a quick look at the extended advertising links you mentioned.

 

I assumed the general GAP protocol does similar stuff (as you showed) but doubted that it could just set data on a set channel.

I still do not see any parameter where I can set my own frequency… This is the main part that I have been working on for a while now.

Does this mean I DO have to use the ll_sw files?

 

(Wrote this as I was reading through your provided documentation)

As I understand, the ‘bt_le_adv_param parameter of the create method’ has a 32 bit options field (0-17 actually used?).

In these options we have:

  • Bit 10 telling to make use of the extended advertising (which I assume are the 255 byte payload messages). It usually sends a smaller header packet first on the primary channels that points to the actual data packet.
  • Bit 15-17 disable the advertising on the normal advertising channels. Does this mean that the previous process behaves differently? Or just skip the first ‘small header’ part?

 

 

Thanks!

 

Steven

 

 

From: Chettimada, Vinayak
Sent: dinsdag 15 december 2020 20:17
To: stevenghekiere@...; Marciano Preciado
Cc: users@...
Subject: RE: [Zephyr-users] Zephyr Low Level BLE Radio question

 

Hi,

 

If you are building a Bluetooth Low Energy application using Zephyr, then you should use the public APIs, not call internal subsystem functions unless you know what you are doing.

 

I think you are looking for the below mentioned options when calling bt_le_ext_adv_create (https://docs.zephyrproject.org/latest/reference/bluetooth/gap.html#c.bt_le_ext_adv_create)

https://docs.zephyrproject.org/latest/reference/bluetooth/gap.html#c.@...

https://docs.zephyrproject.org/latest/reference/bluetooth/gap.html#c.@...

https://docs.zephyrproject.org/latest/reference/bluetooth/gap.html#c.@...

 

These are for the primary advertising channels, auxiliary PDU channels selection is controller implementation specific.

 

If you are not using Bluetooth Low Energy stack, then you should refer to nRF52840 product specification for implementing your proprietary radio protocol.

 

>The low-level bluetooth controller is tragic. I’m sure it’s incredibly useful, but the use of nicknames and acronyms at every corner are not useful. Perhaps if there were comments that could help too

 

Contributions to improve the code, comments and add new features are always welcome.

 

Regards,

Vinayak

 

 

From: users@... <users@...> On Behalf Of steven ghekiere via lists.zephyrproject.org
Sent: 15 December 2020 19:48
To: Marciano Preciado <marciano@...>
Cc: users@...
Subject: Re: [Zephyr-users] Zephyr Low Level BLE Radio question

 

Hey Marciano,

 

Thanks for the quick reply!

I’d have to agree on the acronyms and such.

 

What do you mean that ‘somebody can help us’?

 

Thanks

 

Steven

 

 

 

From: Marciano Preciado
Sent: dinsdag 15 december 2020 19:15
To: stevenghekiere@...
Cc: users@...
Subject: Re: [Zephyr-users] Zephyr Low Level BLE Radio question

 

Hey Steven!

 

I’d have to agree! The low-level bluetooth controller is tragic. I’m sure it’s incredibly useful, but the use of nicknames and acronyms at every corner are not useful. Perhaps if there were comments that could help too, but there aren’t. 😭

 

I hope somebody can help us out.

 

Best,

Marciano Preciado
Embedded Systems Engineer
PassiveLogic Inc.
Mobile 801-800-1184

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On Dec 15, 2020, at 7:11 AM, steven ghekiere via lists.zephyrproject.org <stevenghekiere=hotmail.com@...> wrote:

 

 

Hey there,

 

I’m a student working on a project using a Nordic nRF52840 device.

 

The past month or so I’ve been trying countless times to implement some BLE low level methods, first using Nordic SDK and now Zephyr.

More specific, I’d like to be able to set and receive the frequency to transmit data using the bigger 255 byte non-connectable broadcast beacons.

 

I asked about this on the Nordic SDK QA, which pointed me to use the newer low level BLE Zephyr API. (https://github.com/zephyrproject-rtos/zephyr/tree/master/subsys/bluetooth/controller/ll_sw/nordic)

I got some advice in the #Bluetooth channel in the Zephyr Project Slack, who pointed me to use the “lll_chan_set()” method.

However documentation is lacking, to say the least. 

I’ve been struggling and doing this the trial-and-error way but I simply cannot make sure I send something correctly if I can’t receive anything.

 

Therefore, I would really really appreciate it for some clear guidelines, documentation, code snippets, or maybe even a chat on Slack with someone who knows how this works.

Since I’m working with deadlines I’m getting quite stressed and agitated so I REALLY would appreciate some help 😊.

 

Looking forward to your answer,

Steven Ghekiere

 

 

p.s: You can find me on the Zephyr Project Slack (email steven.ghekiere@..., name Steven Ghekiere). Feel free to respond there if this seems easier.

 

 

 

 
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