Nordic nRF905 Radio IC library for AVR microcontrollers.
For an Arduino version of the library see HERE.
https://blog.zakkemble.net/nrf905-avrarduino-librarydriver/
Copy the ./nRF905 folder to your project and add
#include "nRF905/nRF905.h"
to the source files that use the library.
Examples in the examples folder.
Also have a look at nRF905_config.h, that's where you can change which pins are used and things.
Zak Kemble