Spacing between advertising packets

RE: Spacing between advertising packets

Edvin — Tue, 04 Aug 2020 10:30:39 GMT

Indeed. I have seen that before as well. If I remove one of the channels, the sniffer will stop because it is waiting for that packet. If you set up a central project that will scan without connecting, and you print the advertisement channel of the received packets (you may want to add some custom filter of the address or packet, to print only advertisements from one particular device). The advertising report will contain information on what advertising channel the packet was picked up on. Not ideal for sniffing, because you can't follow into a connection, but you can use it to verify that you are only advertising on the channels that you are supposed to.

Best regards,

Edvin

RE: Spacing between advertising packets

deknoob — Tue, 04 Aug 2020 10:01:20 GMT

You are right Edvin, it was the issue with nRF sniffer. With some tricks I am now able to capture two advertising packets on ch37 followed by ch38 and then it gets stuck because ch39 is masked.
Thank you for your help

RE: Spacing between advertising packets

Edvin — Mon, 03 Aug 2020 13:04:08 GMT

Hello,

How do you determine that you don't receive any advertisements at all? I don't think you will be able to see any advertisements using the nRF Sniffer, because it will be waiting for an advertisement on channel 37 before it switches to channel 38, and then 39.

Does the log indicate that you are starting the advertisement? what does sd_ble_gap_adv_set_configure() return? What does sd_ble_gap_adv_start() return?

BR,

Edvin

RE: Spacing between advertising packets

deknoob — Sat, 01 Aug 2020 06:28:08 GMT

Hello,

I am trying now to change advertising channel map. I use fresh install of SDK17, sd140 and blinky example for evaluation.

When I insert this line in advertising_init

    adv_params.channel_mask[4] = 0x80;

just before

    err_code = sd_ble_gap_adv_set_configure(&m_adv_handle, &m_adv_data, &adv_params);

I don't get any advertising at all. To double check, I comment that line and then it works as it should.

What am I doing wrong here.

RE: Spacing between advertising packets

deknoob — Wed, 15 Jul 2020 02:44:02 GMT

Thanks, I see what you mean. I will experiment and hopefully figure out how to set it up.

RE: Spacing between advertising packets

Edvin — Tue, 14 Jul 2020 13:57:17 GMT

Hello,

You can only have one active advertisement set at the time, so it is not possible to have 3 of these in parallel. You can have one that times out and then update it, as you describe, but I believe that the softdevice will give you the timeout when the last advertising packet has been transmitted (but I am not sure). So you may need to use an additional app_timer for this.

One alternative is of course to not use the softdevice, but set up your own advertisements. Although it may be a bit more work on checking how to properly put together the advertising packets, you will have full control of the radio at all times. However, if your advertisements include a scan response, this is quite a bit more complex, because that would also require scanning and replying to scan responses.

Best regards,
Edvin

RE: Spacing between advertising packets

deknoob — Tue, 14 Jul 2020 02:45:41 GMT

Hello,

My device will be advertising with around 10 second advertising interval. I just realised I could set channel map to ch. 37 and then start advertising with 3.1 second interval and advertising duration of 3 second. Then do the same for ch. 38 and so on. Would this work? Or will soft device not allow duration shorter than interval?

Thanks

RE: Spacing between advertising packets

deknoob — Mon, 13 Jul 2020 17:03:01 GMT

Thank you for quick answer.
Yes, I can see it's hardly justifiable to do it outside the soft device. And this method could result in higher power consumption due to increased CPU activity and timer run. But good to know anyway.
Best regards.

RE: Spacing between advertising packets

Edvin — Mon, 13 Jul 2020 13:48:44 GMT

Hello,

Using the softdevice that is not possible without configuring this between each advertising event. You can set a channel map for your advertising, but this remains unchanged until you manually change this channel map. This means that you need to configure the advertising setup every 300ms.

If you want to set a channel mask, you need to adjust some functions in ble_advertising.c.

The reason for this is that the channel mask is stored in p_advertising->adv_params.channel_mask, and p_advertising is set to 0 inside ble_advertising_init(). Add something like:

p_advertising->adv_params.channel_mask = MY_CHANNEL_MASK;

before sd_ble_gap_adv_set_configure().

Then you can e.g. use a timer to trigger ble_advertising_advdata_update(), which you need to call before you call advertising_start() again. You possibly also need to call advertising_stop before both of these.

Remember to also change ble_advertising_advdata_update() to set the new channel mask.

Best regards,

Edvin