PlatformIO Zephyr Settings for nrf21540 FEM

RE: PlatformIO Zephyr Settings for nrf21540 FEM

mwill195 — Tue, 16 May 2023 15:04:03 GMT

Thank you for your reply Bendik, testing is working reliably for now!

RE: PlatformIO Zephyr Settings for nrf21540 FEM

Bendik Heiskel — Tue, 16 May 2023 14:49:00 GMT

Hi,

Based on my understanding of the configs, this should be the correct timing values to use.

The most important part of the timing is that the FEM must be in TX/RX mode before the radio activity starts, if is too late the start of a TX or RX packet will be cut off leading to problems with the connection. Additionally if the PA is turned on after the SoC have started transmitting there will be ringing on the transmitted signal leading to a very wide band of noise around the transmitting frequency.

Since you are planning on moving over to the nRF connect SDK after PoC the current timings should be OK as long as you are not having problems with the connection. If you want to be on the safe side you could increase the offsets to make sure the FEM is ready before the radio starts transmitting/receiving.

Best regards,

Bendik

RE: PlatformIO Zephyr Settings for nrf21540 FEM

mwill195 — Tue, 16 May 2023 14:30:51 GMT

Replying to my own question, I have read over the timings again and gone with the following for our PoC:

CONFIG_BT_CTLR_GPIO_LNA_OFFSET=11

CONFIG_BT_CTLR_GPIO_PA_OFFSET=11

CONFIG_BT_CTLR_GPIO_PDN_CSN_OFFSET=18

This is taking the PDN/CSN offset to be PD to PG time - i.e. the time after releasing power down that we can select TX/RX EN. 18 used (17.5).

The PA and LNA offsets are taken as the time from PG to TRX (the same for both), 11 used (10.5).

Testing works but I would still like to dig into the code to prove to myself it is operating within the timing parameters of the FEM.