nRF21540 Tx Gain Configure

[lshlin]

Hello,

I use ST's mcu + Atmel radio IC + nRF21540 as the FEM. Use Atmel radio IC's IO to control the TX_EN and RX_EN pins for nRF21540 automatically.

I want to change the nRF21540 Tx gain, but not use the default value.  I only configure the nRF21540 NRF21540_REG_CONFREG0's TX_GAIN to 0~31, MODE and TX_EN clear to 0. And then use two IO to  control the TX_EN and RX_EN pins, MODE pin connect to GND. But seems the Tx Gain always is the default value (about 20dB), the user Tx gain is invalid.

If I set the NRF21540_REG_CONFREG0's TX_EN bit to 1 when write TX gain, the user TX gain is valid.

Can I use like this? If it's not, How to change the diffrent Tx gain and use the IO switch the Tx and Rx.

My question is if I clear TX_EN bit of CONFREG0, and the TX gain of CONFREG0 I set was invalid, it seems use the default value (20dB).

[Kenneth]

If I set the NRF21540_REG_CONFREG0's TX_EN bit to 1 when write TX gain, the user TX gain is valid.

Can I use like this?

This is inline with the description in the product specification:
"The Gain word can be set in the same SPI write cycle as TX is enabled from the Program state"
Ref: https://infocenter.nordicsemi.com/pdf/nRF21540_PS_v1.0.pdf 

Kenneth

[lshlin]

Thanks! Yes, I write the TX gain, MODE and TX_EN bits of NRF21540_REG_CONFREG0 at the same time in face. 

In other word if set TX_EN bit to 1 and the TX_EN pin 1, the user TX gain in CONFREG0 is valid, else if clear TX_EN bit to 0 and the TX_EN pin 1, the user TX gain seem invalid?

I want to configure different TX gain and use the TX_EN, RX_EN pins to switch the TX/RX state (It's fast enough). How to configure the REG0~REG3 to let it work.

[Kenneth]

I think figures 2 to 6 and table 4 describe operation states? It's only in program state that it is possible to configure the nRF21540 and set to other states.

Kenneth

[lshlin]

In 5.1: "When PDN is set to 1, the device is activated and
enters Program state. All registers will contain reset values when the device enters Program state."  The PDN pin equivalently  power down + reset register functions. Ididn'trealizethat regs will reset even not lost power.