With all the processing power under the hood of the Atmel ATtiny13 and ATtiny2313 micros, it’s not too difficult to get them interfaced to the I2C bus: some Basic and embedded assembly code will do just nicely.

The I2C bus (a.k.a. IIC or inter-IC bus) as well as integrated circuits designed to work on it, have been described numerous times in this magazine, just look at references [1] and [2] for two recent articles. Although there exist hundreds of ICs with I2C compatibility, each and every one of these will have one specific function it was designed to handle. For example, humidity sensing, relay driving, LCD controlling, data memorising, push button activity detection, keyboard decoding, bus current boosting — you mention it, it’s all available, and cheap too!