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Observer scan rate

Gergo Zsiak
Intellectual 855 points

Other Parts Discussed in Thread: CC2540

Hi All,

I have the following configuration:

  • CC2540-based gadget which broadcasts one message in each 100 ms (tested, sniffer can see all messages).
  • CC2540 USB stick with hosttestapp and on a PC my Python framework for communicationg with it, now configured for observer role.

The problem is, that on the PC can receive only 1-2 scan responses per second on average. I tried to change the following parameters:

  • maximum number of scan responses in init message,
  • minimum time to perform scanning, when performing General Discovery proc,
  • scan interval used during Link Layer Scanning state, when in General Discovery proc (mSec),
  • scan window used during Link Layer Scanning state, when in General Discovery proc (mSec).

After device init I start an active discovery with discovery mode "All", and  I do it always when the previous one has ended. I can't find a good configuration which receives all of the data.

Do you have any ideas? What is the theoritical limit for message rate in observer mode?

Thanks in advance,

Gergo

  • 0
    TI__Mastermind 23440 points

    Hi Gergo,

    You can try to turn off filtering advertisement reports on the dongle via HCI.

    -Type : 0x01 (Command)
    -Opcode : 0xFE30 (GAP_SetParam)
    -Data Length : 0x03 (3) byte(s)
    ParamID : 0x21 (TGAP_FILTER_ADV_REPORTS)
    ParamValue : 0x0000 (0)
    Dump(Tx):
    01 30 FE 03 21 00 00

    Best regards,
    Aslak

  • 0 in reply to Aslak N.
    Intellectual 855 points

    Hi Aslak,

    Thanks for your response, now I can reach about 5-6 responses in one second, however, it is still less than what is expected. My current settings are:

    • max scan responses: 8
    • filter duplicate responses: 0
    • min scanning time in general: 5000
    • scan interval in general: 8
    • scan window in general: 8

    Once a scan has finished, a new discover is stareted, therefore the device scans continouosly. Any ideas to increase speed more?

    Thanks,

    Gergo

  • 0 in reply to Gergo Zsiak
    TI__Mastermind 23440 points

    Hi Gergo,

    Not many ideas. Though if you use a longer scan interval and window you may get more responses. My only reason for thinking this is that the low interval may cut off the reading of some frames while they are being sent.

    Best regards,
    Aslak 

  • 0 in reply to Aslak N.
    Genius 3345 points

    Perhaps it's switching its RF frequency for the scan when some advertisements are being sent.

    The Sniffer operates on a single fixed frequency, so it can see everything broadcast at that frequency.  I think the observer mode scan you're using switches between the three advertising frequencies, so sometimes a broadcast advertisement can get missed.