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What is the difference between general and limited discoverable/adv mode?

Aaron Lee1
Prodigy 40 points

Hi,

Can anyone tell me what is the difference between DEVDISC_MODE_GENERAL and DEVDISC_MODE_LIMITED?

if the answer is discovering "general" or "limited" advertisement then my question will be the difference of broadcasting advertisement with GAP_ADTYPE_FLAGS_LIMITED.

Thanks in advance..

  • 0
    Intellectual 260 points 
    // Use limited discoverable mode to advertise for 30.72s, and then stop, or
// use general discoverable mode to advertise indefinitely
//#define DEFAULT_DISCOVERABLE_MODE             GAP_ADTYPE_FLAGS_LIMITED
#define DEFAULT_DISCOVERABLE_MODE             GAP_ADTYPE_FLAGS_GENERAL

    It says just there in the source code what the difference is.
    The LIMITED mode your Perhipheral is discoverable (it advertises) for 30 seconds,
    in the GENERAL mode the Perhipheral advertises always (as long as it is powered and NOT connected).

    The general mode is often used in setups where you do not have a user interface (no keys for pressing).

  • 0 in reply to Burak Ozhan
    Prodigy 40 points

    Hi Burak,

    Yes, i'm aware of that... maybe i didn't explain clearly about my doubts. In the scan discovery you can select the scan mode as either LIMITED, GENERAL, or ALL... This makes me think there is a difference between Limited and General advertising, if it's just advertising time then it doesn't make sense to have scan discovery mode selection since General and Limited is all the same..

    Anyone knows why have General and Limited selection in  scan discovery mode? thanks

  • 0 in reply to Aaron Lee1
    Intellectual 290 points

    hey Aaron, the difference is about the discoverable TIME, not about the discoverable characteristics, it is LIMITED because after certain time (~30secs) you won't be able to "see" the BLE device anymore unless you reset it or take out and put back again the battery.

    Again the label "GENERAL & LIMITED" talks about TIME constraints not Characteristics.

    Regards

  • 0 in reply to Andrew Ricci
    Prodigy 105 points

    Hi Jeong,

    I have a simple question about the limited discoverable mode. I understood that it limits the device's advertising time at bootup; what I would like to know is if it is possible or not to restart the 30.72s advertising cycle of my device while it is operatiing, from the software, without having to remove and put back its batteries.

    Best regards,

    Robin

  • 0 in reply to Robin Beilvert
    Prodigy 50 points

    Hi Robin,

    Yes it is possible to restart advertising any time:

    uint8_t advStatus = 1;
// Change the GAP advertisement status to enable.
GAPRole_SetParameter(GAPROLE_ADVERT_ENABLED, sizeof(uint8_t), &advStatus);

    Patrik

  • 0
    Prodigy 130 points
    The use of the advertising modes is up to the application. Because General Discoverable Mode is only supposed to be used for 30.72 seconds maximum, a Peripheral can use it to "stand out" among other advertising devices for a short time. A Central can then filter these devices because of the flag.