Much of the software in this project is very similar to the Intruder Alarm project, so just a few things are highlighted here.

Firstly, there is the USB functionality. You might go looking in the code for it, but it isn’t there! The IOIO libraries are written in such a way that there is literally no code to write to make the app work with Bluetooth. This means that we could do any of the projects in this book with Bluetooth instead of USB, without changing a line of code. Well, this is not quite true, as the project in the next chapter relies on being able to turn the pins on and off quickly, and Bluetooth is not quite fast enough.

Code worth highlighting in this project is that used to write to the SD card. The method that does this is called appendToFile: