For a definition of the I2C interface try.... here this is my simplified
description. The most useful fact for the hobbyist to remember is that the I2C interface clock
maybe stopped. The spec' is from zero to a max frequency. This can be very useful when developing an interface
if there isn't a shed full test equipment available. Just write the code to enable single stepping of the clock and use
a led probe on the buss.
Other project's......links below.