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CC2340R5-Q1: Extra LFOSC PPM

sjmizuta
Intellectual 315 points
Part Number: CC2340R5-Q1

Tool/software:

Hello, TI Team,
We are currently in the process of verifying the Extra LFOSC PPM feature. Specifically, we have put a peripheral enabled with LF RCOSC into a packet loss state while connected to a central device, and observed the expansion of the reception window through current.
In experiments where the central device's Connection Interval was set to 200ms and Supervision Timeout to 10 seconds, and the peripheral's ExtraPPM was set to 10,000 ppm, we observed an expansion of approximately 4-5ms immediately after packet loss, which gradually extended to about 15ms just before the Timeout. Since 200ms with 10,000 ppm corresponds to 2ms, this extension seems significantly larger than expected. Is this behavior as you intended? Furthermore, it is puzzling that the behavior remained consistent even when ExtraPPM was set to 50,000.
If you have documentation explaining the detailed operational mechanism of this feature, please let us know. Additionally, is it possible to expedite the expansion behavior?
Best Regards.



  • 0
    TI__Guru 56215 points

    Hi,

    When the device is missing packets consecutively, the window widening will not only consider the LFOSC PPM accuracy, it will also account for the window widening defined in the bluetooth specification.

    Therefore, you will see the RX window opening wider and wider, and this is expected. 

  • 0 in reply to Christin Lee
    Intellectual 315 points

    Hi,

    Thank you for your response.
    I realized that my understanding of the Core Specification was insufficient. Could you please confirm if my understanding below is correct, just to be sure?

    ・Window Widening = (txSCA + rxSCA) / 1,000,000 * Time_of_last_sync + 16µs
    　(The above Window Widening is added to the front and back of the original reception window)

    Furthermore, after varying the ExtraPPM and verifying, we confirmed that a time of (ExtraPPM / 1,000,000 * ConnectionInterval * 2) is added to the Window Widening immediately following packet loss.
    Is this correct? If not, could you provide the correct formula?

    Additionally, when we set ExtraPPM to 500/1500/5000/10000, we observed that the window expanded up to ExtraPPM = 10000, but there was no change in results when set to 50000.
    If there is an upper limit for ExtraPPM, could you please let us know?

    Lastly, when using the CC2340R5-Q1 without LFXT, could you recommend the appropriate ExtraPPM setting?

    Best Regards.