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SIMPLELINK-CC26X2-SDK: Multi role (scan + advertise)

eteom
Intellectual 370 points

Part Number: SIMPLELINK-CC26X2-SDK

Hi,

When enabling scan and advertise simultaneously delays of up to 500 ms for sending advertisements were observed for advertising interval 100 ms. While pointed out that timing delays can occur trying to scan and advertise at the same time since the CC26x2 is trying to interleave advertising/connection events, reducing scan window and scan interval from 500ms to <100ms seems to mostly avert this issue. So is it right to conclude that during a scan window advertisements get blocked? While reducing scan window and scan interval to say 30ms is acceptable, will this increase chance for packet loss due to delay in channel switching or other delays during which device is not scannin, since these would occur much more frequently with the changes. Cant find any mention of delay between scan windows, is there any documentation, I'm assuming about 100uS. Also just to confirm during a scan window it scans in only one channel, i.e channel switching is window to window,right?

Thanks in advance

  • 0
    TI__Guru 73541 points
    Hi Eteom,

    There is an internal prioritazation in the BLE scheduler that will decide whether to scan, advertise or attend a connection event if these are in conflict.

    If you are in a connection with zero slave latency, connection events will always have the highest priority. In this case, scanning can be scheduled if there is enough time between connection events (about 15 ms required).

    I don't fully understand your situation. Is your device simultaneously scanning, advertising and in a connection? Is the device the master or the slave in the connection?

    For definitions of scan window, scan interval and scan duration, please see the BLE scanning and advertising Simplelink Academy lab: dev.ti.com/.../

    In this situation I think it would be useful to look at the RF pins, to get an overview over the timings in the situation. Can you attach a logic analyzer to the RF pins and post a capture? (You can find instructions for routing the RF pins in the Technical Reference Manual (http://www.ti.com/lit/swcu185 ), chapter 13.3.2.1 Control External LNA/PA (Range Extender) With I/Os.
  • 0 in reply to Marie H
    Intellectual 370 points

    The device would be peripheral + observer role, it will not be in a connection. Continuous scan is enabled after scan is initialized, and it sends advertisements at 100ms interval. For any advertising interval less than scan window, interval the advertisements were sent at an interval greater than scan window, scan interval. So leading to assumption that the advertisements cannot be sent during a scan window. Is this assumption correct or is there some other reason for this?I will look into RF pins for scan timings, the link provided answers the other question.

  • 0 in reply to eteom
    TI__Guru 73541 points
    Hi Eteom,

    As far as I know, this is expected behavior. If you want your device to advertise at 100 ms, you should set the scan window lower than 100 ms.