“The BeagleBone is a inexpensive, credit-card sized computer with many I/O pins. These pins can be easily controlled from software, but it can be very mysterious what is really happening. To control a general purpose input/output (GPIO) pin, you simply write a character to a special file and the pin turns on or off. But how do these files control the hardware pins? In this article, I dig into the device drivers and hardware and explain exactly what happens behind the scenes. (Various web pages describe the GPIO pins, but if you just want a practical guide of how to use the GPIO pins, I recommend the detailed and informative book Exploring BeagleBone.) This article focuses on the BeagleBone Black, the popular new member of the BeagleBoard family. If you’re familiar with the Arduino, the BeagleBone is much more complex; while the Arduino is a microcontroller, the BeagleBone is a full computer running Linux. If you need more than an Arduino can easily provide (more processing, Ethernet, WiFi), the BeagleBone may be a good choice.”