While messing around with twi (that’s what atmel calls i2c) some time ago, i built this little device that does nothing more than listening to the bus and display all the bytes it receives on a two-digit 7-segment-display in hex-format. the motivation for this project was not only “i need this thing” but also “i’m tired of coding and want to solder something. and i have to get rid of these displays anyway”. the schematic and layout was done in eagle. an atmega8-controller (overkill) handles bus and display. the whole device is powered by the bus.
here’s two pics:
yes, i forgot one line 😦