RE: Thingy53 ESB and FEM

Kenneth — Thu, 29 Aug 2024 11:05:52 GMT

Sorry no.

Kenneth

RE: Thingy53 ESB and FEM

carefree — Thu, 29 Aug 2024 09:55:02 GMT

Does Gazell support FEM?

RE: Thingy53 ESB and FEM

Petri Haavisto — Mon, 03 Jun 2024 17:57:47 GMT

Hi!

Thank you for the confirmation!
I tried again and it is now working, at least to some extent.
My initial problem was that when I took FEM into use (CONFIG_MPSL_FEM=y) I also did the following:
CONFIG_MPSL_FEM_NRF21540_RUNTIME_PA_GAIN_CONTROL=y
CONFIG_MPSL_FEM_POWER_MODEL=y

These are both explained in the link you provided and they seemed like a good idea when I actually wanted to control the power dynamically;-)
However, this did not compile for Thingy53 and I made the quick (wrong) conclusion that FEM is not supported.
Now that I looked into this again, I noticed that it was only the setting CONFIG_MPSL_FEM_POWER_MODEL that causes the problem. It will not compile complaining that "undefined reference to `mpsl_fem_power_model_to_use_get'". I verified this with the simplest esb_prx() sample code by just adding that config parameter, and it will not work. This is not a problem and using the power model would have only been a nice extra.

I am still confused about whether this CONFIG_MPSL_FEM_NRF21540_RUNTIME_PA_GAIN_CONTROL really allows me to set power freely within the FEM range. The role of CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA and CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTB is a bit unclear since parts of the link seem to suggest that only those two values should be used. That does not make much sense so I assume it means something else. I have not yet been able to measure whether TX power actually changes more than between two different values.

Regarding ANT1/ANT2 choice, my current assumption is that there simply is no need to use ANT2. I don't think that I can just control antenna selection externally from FEM control since the same line is connected to FEM power-down pin. Since there is no run-time option in ESB to switch antennas (and hence power-down the FEM) I am sure ESB would get confused if FEM would be powered down. I only wanted to have run-time switching between the antennas for test purposes, but compile-time changing is fine as well.

However, this question is clear to me now. Thank you for a very quick response!

Petri

RE: Thingy53 ESB and FEM

Kenneth — Mon, 03 Jun 2024 11:26:24 GMT

Hello,

Yes it's supported, see here:
https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/protocols/esb/index.html#ug-esb

Each time a transmission is triggered, the ESB protocol will update the output power according to the latest that was provided by esb_set_tx_power(). You can see how this is handled by the update_radio_tx_power() that occurs internally in the ESB protocol:
https://github.com/nrfconnect/sdk-nrf/blob/main/subsys/esb/esb.c#L1106

If you need to select antenna pin, then this must be handled directly by the application by controlling the ANTSEL pin.

Kenneth