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.
The BeagleBone uses the Sitara AM3358 processor chip running at 1 GHz – this is the thumbnail-sized chip in the center of the board above. This chip is surprisingly complicated; it appears they threw every feature someone might want into the chip. The diagram below shows what is inside the chip: it includes a 32-bit ARM processor, 64KB of memory, a real-time clock, USB, Ethernet, an LCD controller, a 3D graphics engine, digital audio, SD card support, various networks, I/O pins, an analog-digital converter, security hardware, a touch screen controller, and much more. To support real-time applications, the Sitara chip also includes two separate 32-bit microcontrollers (on the chip itself – processors within processors!).
The main document that describes the Sitara chip is the Technical Reference Manual, which I will call the TRM for short. This is a 5041 page document describing all the feature of the Sitara architecture and how to control them. But for specifics on the AM3358 chip used in the BeagleBone, you also need to check the 253 page datasheet. I’ve gone through these documents, so you won’t need to, but I reference the relevant sections in case you want more details.
Adafruit has had paid day off for voting for our team for years, if you need help getting that going for your organization, let us know – we can share how and why we did this as well as the good results. Here are some resources for voting by mail, voting in person, and some NY resources for our NY based teams as well. If there are additional resources to add, please let us know – adafruit.com/vote
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.