Direction finding - number of IQ samples limited to 82 when sampling CTE with 4MS/s rate (spacing=250ns)

[Thibault]

Hi

I'm using direction finding connectionless_rx project from NRF Connect SDK 1.7.1 with NRF52833 and I want to sample the CTE with a 4MS/s sampling rate (sample spacing=250ns).

I successfully modify params to achieve the 4MS/s sampling rate in radio_df.c. The signal I get after my changes is sampled at 4MS/s as expected.

However, I only get 82 samples. Sampling a 160us CTE with a 4MS/s sampling rate should result in 160*4=640 samples. In HCI.h I found the max number of sample definition B_HCI_LE_CTE_REPORT_SAMPLE_COUNT_MAX and change the value 0x52 (82 int) to 0x280 (640 int). However, this definition seems unused in the project and after this change I still get 82 samples.

What additional change should I do to get the 640 samples?

 

Thanks

Thibault

[Kenneth]

Hello,

It's not a supported feature. Currently only 1us sampling is supported. The HW can support longer/faster, but the implementation does not. So this would require customizing the code, you would unfortunately need to dig deep into the code if you want to try to get longer than 82.

Kenneth