Connection of nRF21540 via SPI interface only

[backstreet.devisor]

Hello everyone!

Please tell me if I can connect nRF21540 to a microcontroller using only 4 SPI pins (SCK, MOSI, MISO, CSN) and control it completely? At the same time I want to leave MODE, RX_EN, ANT_SEL, TX_EN, PDN pins unconnected. 

Thank you.

[backstreet.devisor]

Thanks for the answer!
What if you do the opposite, connect only the MODE, RX_EN, ANT_SEL, TX_EN, PDN pins to the microcontroller, and leave the SPI pins unconnected? Is it possible to do it this way? I need to connect the nRF21540 to the microcontroller with as few pins as possible, but the software implementation should not be too complicated.

[Bendik Heiskel]

Using only GPIO is possible and supported in the nRF Connect SDK.

With only the GPIO interface only 2 different TX gain settings can be used, by default these are 10 and 20 dB.

https://infocenter.nordicsemi.com/topic/ps_nrf21540/chapters/device_control/doc/tx_power_control.html?cp=7_0_0_4_3

If only one antenna is used the ANT_SEL pin does not have to connected to the MCU, and can be grounded directly, this will default to always use the ANT1 pin. This brings the minimum number of MCU pins needed down to 4, MODE, RX_EN, TX_EN and PDN.