Colibri iMX6ULL: Bluetooth seems to connect only with antenna in AUX

Hi team,

I’ve been helping a customer use Bluetooth recently in our Colibri iMX6ULL and I’ve been struggling a bit to get Bluetooth to work in a single antenna configuration, so I’ve been doing some tests and I would greatly appreciate some confirmation.

I always start with the following just to confirm that Bluetooth is running:

systemctl start bluetooth.service
systemctl enable bluetooth.service
connmanctl enable bluetooth

Coming from the V1.0 with a single antenna configuration, I tried a single antenna that even though is not optimal, I believe it should minimally work. So I connected the antenna to the MAIN terminal. However I’ve been unable to connect to anything, or get the colibri-imx6ull to appear in the other device. I’ve also tried the single antenna configuration, but without any changes (which led me to think this would probably be only for WiFi connections). Also, it made me think that 2 antennas would also be needed.

So, in one of the tests, I simply changed the antenna port of the antenna used from MAIN to AUX which, for my surprise, Bluetooth worked as expected and connections where picked up as well as the V1.0A. For confirmation, I asked Azurewave for the module datasheet, and indeed: The AUX terminal is also for the Bluetooth and no reference for BT can be found in the MAIN terminal (A bit counterintuitive I must say…)

Would you kindly confirm that there is no problem to leave the MAIN terminal unconnected for a only? Or ius there any change needed to change the PHY configuration in case we are not using WiFi at all to make it “safe”?

Thanks and kind regards,

Hey @alvaro.tx!

Did you try using a 50 ohm terminator in AUX and the antenna in MAIN? It’s the recommended setup here and we have a customer using this configuration.

Hey @gustavo.tx , thanks for the answer. No, I haven’t. I’ve seen the setup but I’m not completely sure if it would apply to BT (as opposed as WiFi). Do you happen to know any MHF4 50 ohm terminator?

@alvaro.tx I haven’t found an MHF4 50 ohm terminator easily available. Apparently the customer was going for a MHF4 to SMA adapter (like the ones shipped with our antennas) then using a SMA 50 ohm terminator.