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BLE Multi-Link connection - Maximum devices

believer

Hi,

I am currently using NRF52832 with SDK17.0.0.

As I know, a BLE central device can reach up to 20 peripheral devices.

So if I use an Android App as a central device, can I have more than just 20 connections?

Thank you.

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  • 0

    Hi,

    I doubt so, because an Android device will limit the number of concurrent connection to only 7 as defined with BTA_GATTC_CONN_MAX (please see Android Bluetooth stack).

    Also, the SoftDevice limits total number of concurrent connections to 20 (i.e. as central + peripheral). However, it should be possible to maintain more than 20 non-simultaneous links, i.e. maintain number of connection handles below the limit.

  • 0 in reply to Mishka
    Mishka said:
    However, it should be possible to maintain more than 20 non-simultaneous links, i.e. maintain number of connection handles below the limit.

     I don't think so. The limitation is in the SoftDevice's scheduler and memory. The maximum number of linked devices depends on how much memory you've got and how much memory is required for each link depending on the content of the linking information. 

    -Amanda H. 

  • 0 in reply to Amanda Hsieh

    Hi Amanda,

    thanks for the clarification. With "non-simultaneous links" I mean that it's possible to know about more than 20 devices (i.e. keep bonding information), but not get into formal connection with them. On central, the application scanner may catch some more devices and the app could decide to drop few existing connections in favor of the new discovered. Will that work?

    I admit it's unfair to call this kind of operation a link. Sorry for the confusion.

  • 0 in reply to Mishka

    Hi Mike,

    Mishka said:
    With "non-simultaneous links" I mean that it's possible to know about more than 20 devices (i.e. keep bonding information), but not get into formal connection with them. On central, the application scanner may catch some more devices and the app could decide to drop few existing connections in favor of the new discovered. Will that work?

    The limit of 20 is 20 concurrent links at the same time, that is 20 devices that are in a connection right now. We do not have a number for how many bonds the application can store (this is outside the scope of the SoftDevice, who only controls the current connections.)

    So yes, the application can do as you suggest.

    -Amanda H.

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  • 0 in reply to Mishka

    Hi Mike,

    Mishka said:
    With "non-simultaneous links" I mean that it's possible to know about more than 20 devices (i.e. keep bonding information), but not get into formal connection with them. On central, the application scanner may catch some more devices and the app could decide to drop few existing connections in favor of the new discovered. Will that work?

    The limit of 20 is 20 concurrent links at the same time, that is 20 devices that are in a connection right now. We do not have a number for how many bonds the application can store (this is outside the scope of the SoftDevice, who only controls the current connections.)

    So yes, the application can do as you suggest.

    -Amanda H.

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