nRF52840 - s140 - MTU and DLE explain

RE: nRF52840 - s140 - MTU and DLE explain

Nikosant03 — Thu, 17 Dec 2020 11:23:40 GMT

Thanks Keneth,

I will have some tests with the sniffer as well.

RE: nRF52840 - s140 - MTU and DLE explain

Kenneth — Thu, 17 Dec 2020 10:14:40 GMT

The first figure on the page I linked show this I believe:
https://www.novelbits.io/bluetooth-5-speed-maximum-throughput/

So in essence it is 7 bytes overhead, so if "exchanged" DLE max size is 50bytes then I agree that the "effective" payload will be 43bytes in each packet.

RE: nRF52840 - s140 - MTU and DLE explain

Nikosant03 — Thu, 17 Dec 2020 09:08:26 GMT

Hi Keneth,

I noticed I mistake with my calculations. The ATT payload should be 43bytes..

1st packet: 50Bytes (7bytes overhead + 43bytes ATT Payload)

2nd packet: 50Bytes (7bytes overhead + 43bytes ATT Payload)

3rd packet: 50Bytes (7bytes overhead + 43bytes ATT Payload)

4th packet: 50Bytes (7bytes overhead + 43bytes ATT Payload)

5th packet: 35Bytes (7bytes overhead + 28bytes ATT Payload)

43+43+43+43+43+28 = 200bytes

Also in here I read that when there is fragmentation the L2CAP overhead do not added to the fragments as shown from the figure below

With that saying I am not sure If my calculations are correct.. Whould you please refine?

RE: nRF52840 - s140 - MTU and DLE explain

Kenneth — Tue, 15 Dec 2020 12:27:21 GMT

Hi, this seems right, you may also find this page useful that also take into account some of the other parameters that affect throughput:
https://www.novelbits.io/bluetooth-5-speed-maximum-throughput/

Kenneth