One of the important pieces of information that might be useful for your project is its direction of travel. This could be given by a GPS unit, but a GPS unit can be expensive, and it often doesn't work well inside buildings. You can also just "keep track" of the direction associated with your hardware, but you'll need to carefully update this whenever your project might move. Using a compass frees you from always having to keep track, and will also allow you to avoid inaccuracies that can accumulate from inaccuracies in your control system. So, let's learn how to hook up a digital compass to the Galileo.

There are several chips that provide digital compass capability; one of the most common is the HMC5883L 3-Axis Digital Compass chip. This chip is packaged onto a module by several companies, but almost all of them result in a similar interface. Here is an image of one by a company called SainSmart, that is available at a number of online retailers...