For a circuit that uses the I2C buss in an AM Radio with PLL synthesized tuning, frequency set from the PC printer port. here

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......

The three transistor's at the top of the diagram allow the parallel port to be used in a simple manner. Splitting the data into seperate read and write buss.

AM PLL Synthizer Radio