TX gain control when using nrf5340 + nrf21540.

RE: TX gain control when using nrf5340 + nrf21540.

Sigurd Hellesvik — Wed, 14 Jun 2023 11:28:39 GMT

Can you read over the answers in nRF21540 SPI Gain Dynamic Control and see if you still have the same questions after that?

If you do still have questions, it would be useful if you list "expected TX power" and "measured TX power" outputs.

Edit:
Also, can you send me your build/zephyr/zephyr.dts file?

Regards,
Sigurd Hellesvik

RE: TX gain control when using nrf5340 + nrf21540.

Noah_iR — Wed, 14 Jun 2023 00:33:40 GMT

When I read "NRF_RADIO->TXPOWER" register in decimal, it will appear as below.

1. CONFIG_BT_CTLR_TX_PWR_ANTENNA=0........ TXPOWER : 244

2. CONFIG_BT_CTLR_TX_PWR_ANTENNA=5........ TXPOWER : 251

3. CONFIG_BT_CTLR_TX_PWR_ANTENNA=10........ TXPOWER : 0

4. CONFIG_BT_CTLR_TX_PWR_ANTENNA=15........ TXPOWER : 0

This value is output the same whether I set the mode pin to ACTIVE_HIGH or ACTIVE_LOW in the dts setting of the nrf21540 FEM.

Of course, depending on the mode pin setting, there is a difference of about 10db when measured with Tektroxix's Spectrum Analyzer.

Based on the results measured so far, it seems that the library fixes the gain of FEM to a specific value(10db for nrf21540) and lower SoC's TX gain based on that value.

RE: TX gain control when using nrf5340 + nrf21540.

Sigurd Hellesvik — Tue, 13 Jun 2023 10:52:58 GMT

Hi,

[quote user=""]But when I measured it with an spectral analyzer, there was a difference of about 13db.[/quote]

How much did you measure?

Can you read out the output power from the nRF5340?

You can do this by reading the TXPOWER register.
This can for example be done while debugging.

Regards,
Sigurd Hellesvik