Antenna switching

[theo17]

Hi

I have a question concerning AOA.

I have already make a tx (with nrf52833) and a rx (nrf52833 too) and i succeed to receive the CTE and the IQ sampling with the antenna onboard but now i want to use an antenna array as receptor. My question is that : wich pins on nRF52833 are configured in the program "direction_finding_connectionless_rx" for control antenna switching ??

If you can help me i'm more than interested

[Didrik Rokhaug]

Hi,

You can find (and change) which pins are used for antenna switching in the nrf/samples/bluetooth/direction_finding_connectionless_rx/boards/nrf52833dk_nrf52833.overlay file.

Best regards,

Didrik

[theo17]

Thank you so much for the reply !!

I modified the wrong files (i have a copy of my project and i change the wrong files) but now it's right i can see the good signal on the pins 3 and 4!

But now i had another question because i have the impression that my program doesn't receive the IQ data for all the antenne. Can you help my on that too ?

Here is the modified fonction in the main to print IQ data :

Here is what my nrf52833 receive:

[Didrik Rokhaug]

To me it looks like you have all the 45 samples you should have. What makes you think that you don't get all the IQ data?

I would also like to add that the IQ data itself isn't very useful. You also need an (antenna specific) direction finding algorithm to convert the IQ data into a vector form.

Nordic will not provide the direction finding algorithm, and customers/users are expected to get that elsewhere. In order to use the IQ data you get from the beacon you will need an AOA algorithm, which we don't provide. There is no point in looking at the raw data as it needs to be converted into vector form to review it properly. You can check out this page for information on the various formulas used to translate IQ data between polar and rectangular form.

[theo17]

The data are wrong because i disconnect my antenna number 3 (my antenna array have 4 antenna) and when i look at the IQ data i don't see any 0 or very very low values for IQ

[Didrik Rokhaug]

Even though one of the antennas are disconnected, you will still get a sample from it (assuming that you sample it), and it is not given that you will get low values.

I cannot see anything obviously wrong from the screenshots you have attached, but as I said in my previous reply, you must figure out most of the SW yourself.

P.S. I see that I am missing a link in my previous reply. I have added it now.