Odd scanning behaviour since NCS 2.6.1

[Phobios]

Hi,

I'm seeing a slow and odd scanning behaviour since I updated my toolchain and NCS to 2.6.1.

To my setup:

• I have two NRF52840, one acting as peripheral, the other as central.
• The peripheral is connected to the central with connection parameter: 200ms, latency 9
• Additional I'm sending an advertisement Beacon every 100ms

In the central I've set the scanning parameter "scan interval" and "scan window" to 200. According to this post and the answer this is the right way to do it. Also I have a name and a mac filter running. https://devzone.nordicsemi.com/f/nordic-q-a/109512/scanning-parameter-settings-to-get-the-most-advertisements-but-also-handle-connections

Now to my problem:

• Flashing the central with NCS 2.5.1 everything works fine. I have a solid connection to the peripheral and almost every advertisement package is received, so ca. 10 per second
• Flashing the same code with NCS 2.6.1 I'm only receiving 1 or 2 advertisement packages every 3 seconds.

Do you have any idea why the behaviour has changed? Did you change anything in the scanning section during the last release?

Thanks and Best Regards,

Phobios

[Amanda Hsieh]

Hi, 

• Flashing the central with NCS 2.5.1 everything works fine. I have a solid connection to the peripheral and almost every advertisement package is received, so ca. 10 per second
• Flashing the same code with NCS 2.6.1 I'm only receiving 1 or 2 advertisement packages every 3 seconds.

Do you use the same peripheral device for these two situations? What is the NCS version and application on the peripheral device? Could you use the nRF Sniffer for Bluetooth LE to check the advertisement packages?

We are currently understaffed due to the summer vacation period, so delayed replies must be expected. I am sorry about any inconvenience this might cause.

Regards,
Amanda H.

[Phobios]

Yes the peripheral device is the same. Same hardware & same firmware for the tests. It uses NCS 2.6.1

I don't have the sniffer at hand, but I checked the advertisements with the NRF Connect App - I receive them at a rate of 10Hz (100ms); so the peripheral is definitely working.

[Amanda Hsieh]

Could you try the latest v2.7.0? Do you see the same issue?

[Phobios]

With v2.7.0 it's the same behaviour as with v2.6.1. But I've done some more tests and I have narrowed it down. You see, in my system I have more than one peripheral connected. And as soon as I establish a second connection the problem occurs and I miss a lot of advertisement packages. So the facts are:

• One peripheral connected and sending out beacons: Everything is fine with 2.5.1, 2.6.1 and 2.7.0
• Two peripherals or more connected and sending out beacons: Only 2.5.1 works, with 2.6.1 and 2.7.0 I'm getting nearly no advertisement packages

The peripherals itself all have 2.6.1, and the advertisements are sending out fine (checked with mobile phone and nrf Connect App)

[Amanda Hsieh]

Have you tried other scan parameters besides interval = window = 200ms?