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APP_ADV_DIRECT_INTERVAL

astella

To the kind attention of Nordic support team,

We would like our BLE nRF52 based product to reconnect as fast as possible.

My question is: are there side effects in having directed interval too small?

I mean, could have energetic implications, but anything else bad to consider?

How low can we set it?

Thank you for your kind advise.

Best regards

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  • +1

    Hello,

    We would like our BLE nRF52 based product to reconnect as fast as possible.

    When you say reconnect, do you mean as a result of an accidental disconnect - such as if the connections times out?
    You can see all the possible advertising types here, for the fastest reconnection you should use the BLE_GAP_ADV_TYPE_CONNECTABLE_NONSCANNABLE_DIRECTED_HIGH_DUTY_CYCLE.
    What is your applications latency requirement with respect to reconnection?

    My question is: are there side effects in having directed interval too small?

    The main side effect of having a very small advertising interval is the increased power consumption.

    I mean, could have energetic implications, but anything else bad to consider?

    The smaller the interval between advertisements, the bigger the current consumption will be. This is because the radio consumes a lot of power, and therefore the more you use it, the higher your average current draw will be. You should also consider the fact that if the disconnected device frequently disappears or changes the directed advertisement will not work, and will thus be wasted. This is something worth considering when using directed advertisements if the peer will often change.
    Since the directed high duty cycle advertising advertises with an interval less than 3.75 ms, this is quite extreme in the BLE sense, and is mainly meant for cases where low latency reconnection is important, and power consumption is less important.
    The directed high duty cycle advertising can maximally advertise for 1.28 s, to avoid impeding surrounding wireless traffic.

    How low can we set it?

    The directed advertising interval? This depends on your central, but I assume it will start scanning again immediately upon a connection termination, in which case you wont have to advertise for very long, if the central is still within range. If there is a lot of noise in the environment, or that the accidental disconnection likely happened because the central moved out of range, you will need to advertise for longer, to compensate for the possibility that the central does not see all the advertising packets.
    If this happens, it is advisable to rather move to slower directed advertisement.

    Best regards,
    Karl

Reply
  • +1

    Hello,

    We would like our BLE nRF52 based product to reconnect as fast as possible.

    When you say reconnect, do you mean as a result of an accidental disconnect - such as if the connections times out?
    You can see all the possible advertising types here, for the fastest reconnection you should use the BLE_GAP_ADV_TYPE_CONNECTABLE_NONSCANNABLE_DIRECTED_HIGH_DUTY_CYCLE.
    What is your applications latency requirement with respect to reconnection?

    My question is: are there side effects in having directed interval too small?

    The main side effect of having a very small advertising interval is the increased power consumption.

    I mean, could have energetic implications, but anything else bad to consider?

    The smaller the interval between advertisements, the bigger the current consumption will be. This is because the radio consumes a lot of power, and therefore the more you use it, the higher your average current draw will be. You should also consider the fact that if the disconnected device frequently disappears or changes the directed advertisement will not work, and will thus be wasted. This is something worth considering when using directed advertisements if the peer will often change.
    Since the directed high duty cycle advertising advertises with an interval less than 3.75 ms, this is quite extreme in the BLE sense, and is mainly meant for cases where low latency reconnection is important, and power consumption is less important.
    The directed high duty cycle advertising can maximally advertise for 1.28 s, to avoid impeding surrounding wireless traffic.

    How low can we set it?

    The directed advertising interval? This depends on your central, but I assume it will start scanning again immediately upon a connection termination, in which case you wont have to advertise for very long, if the central is still within range. If there is a lot of noise in the environment, or that the accidental disconnection likely happened because the central moved out of range, you will need to advertise for longer, to compensate for the possibility that the central does not see all the advertising packets.
    If this happens, it is advisable to rather move to slower directed advertisement.

    Best regards,
    Karl

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