4 Replies Latest reply on Aug 29, 2016 8:46 AM by MiTo_1583836

    BLE_CEN_CFG intervals and windows

      Regarding parameters in BLE_CEN_CFG ...


      "high_scan_duration" means how long to be in high scan state?

      "high_scan_interval" slots means do a scan every this many slots?

      "high_scan_window" slots - what means this?


      How long is 1 slot ?


      When does central state machine change from high scan to low scan?

      How can we keep it always in high scan mode?



        • 1. Re: BLE_CEN_CFG intervals and windows

          Scan is not about sending packets, but about putting radio in to the listen mode, i.e. listening for advertisement packets.  Interval defines the time between two consecutive scans.  Window is the duration of one scan. 1 slot is 0.625 milliseconds.  Defaults for high duty scan are interval 96 and window 48.  The radio will start listening every 60msec and will listen for 30msec, then it will go to sleep or do whatever else in needs to do.  Defaults for low duty scan are 2048 and 18.  Meaning every 1.28sec listen for 11.25msec.


          High Scan Duration is how long to perform high duty scans in seconds before switching to low duty scan.  If you always want to stay in the High Scan mode you can start the timer for the High Scan Duration, and then start High Scan again.

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          • 2. Re: BLE_CEN_CFG intervals and windows

            Is it possible to increase the window up to 90% of the interval? Is Interval 96 and window 87 still a safe option (from the stack point of view)?


            That would be for designs that require active scanning to perform a connection as quickly as possible with a sensor.



            • 3. Re: BLE_CEN_CFG intervals and windows

              Theoretically you should be able to scan 100%.  But it would be easy to test. I saw application scanning 32/30. You can also scan 100% and have another connection.  The stack should be smart enough to interrupt the scan, service connection and go back to scan again.

              • 4. Re: BLE_CEN_CFG intervals and windows

                Thanks Victor for the quick answer, really appreciate it!