Issue using SKY66112-11 FEM with Distance Measurement Example on NORA-B126 (nRF5340)

[_lumac]

Hello Nordic Team,

I’m currently developing a BLE ranging device using the u-blox NORA-B126 module, which integrates an nRF5340 SoC and a Skyworks SKY66112-11 FEM.

I’m encountering an issue when running the distance measurement (DM) example. The symptoms are as follows:

• When the FEM is properly configured, the distance measurement example does not perform any ranging measurements, it appears idle with no error messages.

• When the FEM configuration is removed, the example runs for around 5 minutes before halting unexpectedly.

• The FEM appears to function correctly by the way; for instance, it yields a notable -23 dB improvement when tested with the LBS (LED Button Service) example, which suggests proper PA/LNA operation.

We are configuring the FEM as described in the NORA-B1 System Integration Manual, starting from page 19, with GPIO forwarding and MPSL settings in the board support package, following NCS v2.0+ guidance.

I’m using the DM example without any code modifications, except enabling the FEM as per documentation. It’s unclear if the DM stack has built-in support or limitations when used with MPSL FEM routing. If any diagnostic tools or debug flags could help trace radio state transitions or FEM behavior, I’m open to suggestions.

Questions:

1. Is the Distance Measurement (DM) example compatible with the use of a FEM (e.g., SKY66112-11)?

2. If so, are there additional or missing FEM configuration steps (e.g., GPIO forwarding, MPSL FEM driver setup, Kconfig, DTS, etc.) that are required for the DM example to function correctly with a FEM on the nRF5340/NORA-B126 platform?

Thanks in advance for your support!

1856.NORA-B1_SIM_UBX-20027617.pdf

[_lumac]

Hi PaKa,

Thank you for the clear and direct answer. I appreciate you confirming that the Distance Measurement (DM) / NDT stack is not compatible with FEMs.

My primary goal for integrating the SKY66112-11 FEM was to significantly extend the ranging distance for our application. Your suggestion to use the FEM in bypass mode makes sense as a workaround to get the example running, but it would unfortunately defeat the purpose of using the FEM in the first place.

From your perspective, is there any recommended Nordic solution or development path to achieve long-range distance measurements that can leverage a FEM? Or is this use case currently outside the scope of the existing stack?

Thanks again for your help!