nRF Connect not supporting DLE on Android or IPhone

[Jim]

When we try and stream BLE data to the nRF Connect app on an Android or IOS phone the app accepts our requested for an MTU of 244 or 160 respectively, however it does not accept our request for DLE. As a result are MTU packets are broken down into 27 byte packets which  takes many connection intervals rather than just one hence our throughput is much lower.

When we use nRFConnect for windows via an nRF dongle we do not get these issues, the dongle accepts our request for our MTU of 244 and DLE.

Do the Nordic nrfConnect apps actually support DLE, or is something else causing this issue?

[Jørgen Holmefjord]

Hi,

It should be supported in Android version of nRF Connect at least. I just tested, and the phone sends a LL_LENGTH_REQ update automatically after the MTU exchange. Are you sure that your phone supports DLE? I tested with a Huawei P30 Pro.

The release notes for nRF Connect for desktop also mentions support for DLE. I do not have iPhone to test with, but I would be surprised if it is not supported.

Best regards,
Jørgen

[Jim]

Hi Jørgen

I think you are correct the particular phone I was using did not support DLE, I tried testing our firmware using a different Android phone as central device and everything work as expected.

From looking at the BLE specs it doesn't appear that DLE is a mandatory requirement for BLE V4.2 or V5, is there as way of checking which Android phone models support DLE without physically testing them?

Kind regards,
James

[Jørgen Holmefjord]

You can check the Bluetooth SIG listings for the phone model. If you are a member, you should be able to read the ICS details and look for the "LE Data Packet Length Extension" in the "LL (Low Energy Link Layer)" section.