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GAP Observer channel restriction

Jacob Portukalian
Prodigy 90 points
Other Parts Discussed in Thread: CC2541

Hello,

I would like to be able to restrict the channels being scanned by a GAP observer/central on a CC2541.  I can't seem to find anything in the documentation that suggests a way to do this.  Am I missing something or is this not possible with the current stack?

Thanks,

Jacob

  • 0
    Guru 22270 points

    Hello Jacob,

    I have only seen restrictions applied to the advertising channels in the source code for peripheral devices. http://e2e.ti.com/support/wireless_connectivity/f/538/t/270443.aspx

    The only place I have seen where you can listen to a specific channel is in the PacketSniffer.  It is probably just the  software filtering out the other channels.

    There does seem to be some wording in the BLE v4.0 that states that the Link Layer shall use all advertising channels when scanning. 

    If you are trying to reduce the amount of time for scanning, you can reduce the size of the scanWindow and scanInterval.

    Thanks,

  • 0 in reply to Greenja
    Prodigy 90 points

    Thanks for the response, even though it doesn't conclusively answer my question.

    I want to restrict the scan channel because I'm trying to see if that reduces the amount of fluctuation in the RSSI measurement.  I'm trying to understand the physics of the RSSI measurement, not optimize battery life at the moment.

  • 0 in reply to Jacob Portukalian
    Guru 22270 points

    I can't provide you with a definitive answer on this one.  I can only suggest options.  

    Instead of trying to restrict scanning, you can restrict the advertising to just one channel and observe the effects on the RSSI.

    Another suggestion would be to use one of the RF tools found in the TI program folder to do your analysis.  You can use the SmartRF Studio or the Link Quality Monitor found in the  Wireless Tools program folder.

    Thanks,

  • 0 in reply to Greenja
    Prodigy 90 points

    Thanks for the tips.  I'm using off-the-shelf beacons right now but I'll try using a dev kit as a beacon with the channels restricted to see if that helps.