Notice that the CSN line on the radio module is connected to SCK ... The master then switches the pin back to input, allowing the nRF24L01+ to control the line, but doesn’t read yet.

[Necromant] wrote a library to flash his microcontroller over an RF link using an NRF24L01 wireless communication module. The NRF24L01 is a cheap RF module that can be easily integrated into ...