@Unbioctian take a look at /usr/lib where the library shared objects are kept and /usr/include where the header files are kept. You'd notice some library objects do not have corresponded header files. The i2c C library is available for you and is called libonioni2c. The source code can be found in our GitHub repo. For more info on compiling C/C++ on the Omega please refer to our official documentation and i2c C Library