Help on driving i2c module

i’m beginner in PX4 but i have good basis on programming and digital electronic.
I would like to drive i2c/pcm module (i.e. with my Pixfalcon board.
I tried to do some simple expetiments, by modifying px4_simple_app example.
Do you know what is the library i have to use? i see many function related to i2c into /modules/px4iofirmware/i2c.c but i can’t find a way to import the library.
do you have any suggestion? need your help
thank you