For SPI, libraries do not treat as CS (although it is shown in some diagrams.) This is just a GPIO pin, but it typically get connected to "CE" (for Chip Enable -- e.g. take chip out of standby.)  It is typically logic LOW.  On the CC1101 it is used for GDO0 (general purpose IRQ).

Generic GPIO uses PB2.

CHECK: "LPTIM1.OUT/COMP1 IN+"

Devices:
- NRF24L01[SPI] (CE)
- NRF24L01[SPI] (CE)
- CC1101[SPI] (GDO0)