In General the question in the title, but there are a couple of nuances.
Google immediately shows github and it would seem - ready:
But I was not able to pick their environment, CodeVisionAvr, the compiler swears.
I really found nothing (don't exclude that was looking bad).
Found several manuals how to raise without all the libraries, but it is too tricky and written in 2009-2012, and to necroposting wrong.
Briefly about the project:
2 атмеги328 master and slave, respectively, the slave is free only 2 pins, though any (i.e. or the UART, or i2c) the master must transmit 2 bytes of information - 2 number: the cell number and the value that you want to put here.
The master should keep the communication on the UART (for receive commands over), and occasionally send these 2 numbers to the slave.
And optional can occur 3 ADC module (or a special IC, attiny44 or(or something like that)) from which you want the wizard to retrieve the values upon request.
Sobstvenno i2c and therefore want that all hung on one bus.