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I2C
The Inter-integrated Circuit (I2C) Protocol is a protocol intended to allow multiple “slave”digital integrated circuits (“chips”) to communicate with one or more “master” chips. Like the Serial Peripheral Interface (SPI), it is only intended for short distance communications within a single device. Like Asynchronous Serial Interfaces (such as RS-232 or UARTs), it only requires two signal wires to exchange information.
Many of the sensors used in the lab will use the I2C protocol. Therefore it is important that you understand what I2C at a fundamental level before you can use it. The sparkfun I2C page provides an excellent introduction so start with that first. Afterwards, the i2c-bus.org website will give a great primer as well as additional resource