How to calculate advertising interval please?

[PingISTL]

Dear Support

I am developing a central application, scan and send out scanned packets via UART to host MCU, where I am thinking of calculate the advertising interval by simply comparing arriving time difference between two advertising packets.  But I found that the result I obtained are quite different with the nRF Connect App shows, and changes a lot, I have a question to ask:

- Is it possible to get advertising interval after UART transmission? there must some time lost between sending and receiving, will the time lost affect the result?

Thank you!

Ping

[Kenneth]

Hello,

The intention is to use periodic advertisement feature for this functionality:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/samples/bluetooth/periodic_adv/README.html

If you want to "follow" legacy advertisment packets, have in mind that in BLE there is a 0-10ms random delay between each advertisment packet as specified by BT core spec.

Best regards,
Kenneth

[PingISTL]

Hello, Kenneth

Thank you for reply!

I am not developing peripherals to do periodic advertising, just simply want to scan any peripherals doing advertising, Am I able to follow them if they are not doing periodic advertising? I don't mind random delay of 0-10ms, the interval between packets on UART receiving line is much big than that, so I wonder whether the original interval is lost over the transmission.

For normal peripherals which not doing periodic adverting,  there is a minimum and maximum interval specified, does this mean their intervals is random between the specified ?

Regards!

Ping

[Kenneth]

Hi,

A peripheral device can advertise any interval between few ms to several seconds, there is no information in the advertisement packet about how frequently it does the advertismenet. As a central device you can only set a scan window and scan interval and hope for the best.

Kenneth

[PingISTL]

Thank you, Kenneth

So, for a particular peripheral, does this mean I am not be able to measure its advertising interval by scanning two packets and calculate the time interval in between?

Regards!

Ping 

[Kenneth]

Yes and no. Have in mind though the peripheral can change the interval.

edit: and that the measurement might be influenced by a up to 10ms random delay.

Kenneth