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[antoine98]

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[Sigurd]

Hi!

The security itself should not have an impact on the throughput . Likely something else changed, like connection interval, PHY used, etc

[antoine98]

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[Sigurd]

Hi!

Could you try to capture a sniffer trace, one for the fast speed and one for the low speed case.

https://www.nordicsemi.com/Products/Development-tools/nRF-Sniffer-for-Bluetooth-LE

[antoine98]

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[Sigurd]

Could you save the traces, and upload them here?

[Sigurd]

Hi,

You have many more numbers of packets sent each connection event with the fast one. The slave always have the MD(More Data) bit set, and the connection event goes on as long as possible.

With slow one, the slave send a few packets, and then the slave indicates that is does not have more data to send:

And the connection event ends. So it seems from the log, that you are not queueing up packets fast enough, and the connection event ends.