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CC3200MOD: Active scanning with hidden SSID, probe requests

Roger Meier
Prodigy 110 points
Part Number: CC3200MOD
Other Parts Discussed in Thread: CC3200

Hi,

We experience some connectivity problems with networks with hidden SSID.

In this case, my understanding is:

1) ANY access point MAY or MAY NOT respond to an active probe request if the SSID is specified NULL in the request

2) only access points with the correct SSID MUST respond to an active probe request if the SSID is specified in the request

Related to this, I have several questions for which I couldn't find an answer in the documentation:

- Are probe requests from the CC3200 containing the SSID or not? - if not, it means depending on the security settings, an AP might or might not respond to the request?

- Knowing the SSID, is there a way to "scan" a network with active probing? - what I would like to achieve is to (a) scan all access points in range with a given SSID (b) try to connect to each of them individually (c) generate a report which (d) would allow to identify an access point that is not configured correctly or not connected to the internet.

- with sl_WlanGetNetworkList command, I understand there is a limitation of 20 stations (I assume a circular buffer?). Will this limitation also apply for the NWPs "active probing" before it connects to an AP? Because of this limit, if there are 30 stations and only 1 of them is configured to a specific SSID, is it possible that the CC3200 actually only rarely "sees" this one station, even when the SSIDs are visible and even if the signal strength of this 1 access point is OK?

Thanks!

- Roger

  • 0
    TI__Guru 63006 points
    Hi Roger,

    The CC3200 uses a combination of broadcast probe requests (SSID=0) and dedicated ones (SSID=<network name>).
    The dedicated probes will be sent upon slWlanConnect or based on available connection profiles.
    The WLANGetNetwork should include all the available networks.

    BTW. the list includes Access Point (networks) names. Stations are devices that connects to an AP and will not appear in the list.

    br,
    Kobi
  • 0 in reply to Kobi Leibovitch
    Prodigy 110 points
    Hi Kobi,

    Thanks, very helpful! - I think I was able to achieve what I wanted.

    In regards to the limitation of 20 stations with sl_WlanGetNetworkList call, are you able to describe how this list is updated from the NWP if there are more than 20 access points in range of the CC3200? (is it a circular buffer that contains the most recently seen access points, or is there some filtering based on RSSI or other?) - it is quite frequent that we have more than 20 access points in range and it would be useful to know if we do several sl_WlanGetNetworkList, e.g. with 50 ms delays, we could get a full list.

    Best,
    - Roger
  • 0 in reply to Roger Meier
    TI__Guru 63006 points
    Hi Roger,

    The filtering of the scanned APs is based on RSSI.
    Retries in a "static" and congested environment are not supposed to show access points with very low RSSI.

    br,
    Kobi