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what is different between TGAP_CONN_SCAN_INT and TGAP_CONN_EST_SCAN_INT.

Ji-won Lee
Genius 3630 points

Hi TI team,

I don't understand exactly the difference between TGAP_CONN_SCAN_INT and TGAP_CONN_EST_SCAN_INT.

#define TGAP_CONN_SCAN_INT            12  //!< Scan interval used during Link Layer Initiating state, when in Connectable mode (n * 0.625 mSec)

I don't understand why this comment is mentioning about 'in Connectable mode' along with "initiating state".

on core v4.2 spec, the connectable mode or connection establishment procedure are used as a different and separate meaning according to peripheral or central device role.

#define TGAP_CONN_EST_SCAN_INT        23  //!< Scan interval used during Link Layer Initiating state, when using Connection Establishment proc (n * 0.625 mSec)

And, my guess is that TGAP_CONN_EST_xxx illustrates that the macro is used after/when connected, that is, connection is establlshed, for example, TGAP_CONN_EST_INT_MIN or TGAP_CONN_EST_SUPERV_TIMEOUT or TGAP_CONN_EST_LATENCY.

if the same concept is being used in naming the macro, is TGAP_CONN_EST_SCAN_INT  for after connected and then just to scan for another devices?


Please let me know.

Ji Won

  • 0
    TI__Genius 11740 points
    Hi Ji Won,

    I see your confusion - the comments can appear to be cryptic. We've noted your feedback, thank you!

    TGAP_CONN_SCAN_INT, and TGAP_CONN_EST_SCAN_INT are just values recommended from the Bluetooth Core Specification ( for two different cases. The common factor here is that the link layer is said to be in the initiating state: the LL will be listening on advertisement channel indices for a duration specified by the scan window and interval. The difference is related to the pattern you pointed out:

    TGAP_CONN_SCAN_INT describes the scan interval when a connection has already been formed - and you're scanning for background information. You'll find that this is much larger than TGAP_CONN_EST_SCAN_INT

    TGAP_CONN_EST_SCAN_INT describes the scan interval when establishing a connection. Much faster than TGAP_CONN_SCAN_INT.

    If you want more information regarding the recommendations checkout: 9.3.11 Connection Establishment Timing Parameters in Vol 3, Part C of the BLE Core Specifications.

    Regards,
    -Rebel
  • 0 in reply to A. Rebel
    Genius 3630 points

    HI Rebel,

    Thanks for your detail explanation.
    These two macro naming is anyway somehow different from the naming pattern of the others for when and after a connection is established like TGAP_CONN_EST_INT_MIN or TGAP_CONN_EST_SUPERV_TIMEOUT or TGAP_CONN_EST_LATENCY.

    I will remember this TGAP_CONN_SCAN_INT is to scan for another devices when/after connected.

    Thank a lot again.

    Ji Won