I2C libraries for attiny85-like AVR micros

A pair of I2C libraries for AVR micros with USI two-wire mode capabilities (developed and tested on attiny85’s, but portable - in theory! - to similar devices with the proper pin changes) + a bunch of examples both with primary and secondary devices.

The goal here is to use them as the main entry point when dealing with I2C in future projects (and improve them over time, of course!), so there’s also a fully functional micro-example of a primary device reading from a secondary device and writing into a third secondary one.

• Github repo with more info about how the libraries work
• Project page on hackaday.io
• Schematics for the example devices