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CC2650DK: SmartRFStudio packet Rx Timestamps don't align with transmitting interval configured for a beacon

Steven Flores
Prodigy 40 points

Part Number: CC2650DK

Capturing packets over-the-air from a BLE using iBeacon format:

I find that with SmartRFStudio 7 and SimpleLink CC2650 Development Kit, the interval between each beacon is off by tens of ms, from what I configured the beacon interval for.  Meanwhile, using the SmartRF Packet Sniffer in combination with the CC2540 USB the packet intervals are within 1-2 ms which is what I expect.  Is this a known issue and if so, is there a fix for it?

I would prefer to use SmartRFStudio and the CC2650DK, because I can capture packets to a text file that I can then process through Excel to get statistical metrics.  With SmartRF Packet Sniffer, there isn't a way that I've found to collect large numbers of packets that can be easily fed into Excel.

Thanks in advance for any assistance that can be provided!

Regards, Steve Flores

Additional information:

I see in SmartRFStudio the following timestamps for the beacon above:

14:09:04.216
14:09:04.372
14:09:04.621

The above intervals come out to 156ms between 1 and 2, and 249ms between 2 and 3.  Yet, the configured interval for the beacon itself is 100ms.  When I check with SmartRF Packet Sniffer, the absolute times show 101ms to 103ms between each packet.

  • 0
    TI__Guru** 106705 points
    Hi Steven,

    Basically, SmartRF Studio is designed as general (PHY) RF test Tool, not an accurate packet sniffer. What you are seeing might just be a limitation with the tool.

    I am notifying one of our Tools guys about your post to provide some more details here.

    Cheers,
    Fredrik
  • 0 in reply to Fredrik K
    Prodigy 40 points

    Thank you Fredrik!  Looking forward to another update with more info.

  • 0 in reply to Fredrik K
    TI__Genius 12900 points

    Hi,

    Fredrik's answer is correct, this is a limitation of how SmartRF Studio handles packet timestamps. The SmartRF Studio timestamps are set by the host machine when the packets are parsed. For example, if there is a lot of traffic on the USB bus, this affects the timestamp, since packets may arrive with a delay. Similarly, if you have other processes running on the machine, this can also affect the timestamp.

    The SmartRF Packet Sniffer can dump data to the .psd format. I know others have written a script that parses the psd file into some format that they can then use to dump into e.g. Excel. The PSD format is explained in the SmartRF Packet Sniffer documentation.

    Hope this helps :)

    TIABO

  • 0 in reply to TIABO
    Prodigy 40 points

    Thanks Tiabo!  I did find a few posts from individuals who wrote parsing routines, as well as a couple who managed to send RF Sniffer captures directly to Wireshark, which I have started using.  My challenge with this method is how to dissect a BLE beacon packet like one using the iBeacon format (for example), as opposed to Zigbee which is what the posts have been focused on.  I chose this method, because the parsing routines seem to have issues with the BLE iBeacon packets.

    Anyway, that's for another group.

    Thanks again!

    Steve