Some of these chips, though, don’t have native SPI or I2C interfaces; instead, everything is done through a USI, or Universal Serial Interface module.

However, for the price, they also often pack in additional interface options like USB-serial and I2C, along with higher update rates. I Need Fast Updates!

A recent newsletter mentioned a testing and debugging module called the “Bus Pirate” that helps people overcome problems with serial buses. People can simulate bus operations for 1-Wire, I2C, SPI, ...

The circuit shown can be used to interface multiple serial devices to the I2C bus, even if they lack the extended-addressing capability required. Information transfer be-tween ...