Single-board computers such as the BeagleBone Black have become more popular due to their low cost of entry for an entire computer, however often lack robust I/O or require a convoluted amount of code to achieve simple hardware tasks.
A neat solution is to communicate with an external microcontroller, and in this example by Joshua Datko you can learn how to upload not only Arduino sketches (in .hex file form) to a bare Arduino-compatible microcontroller circuit and also enable serial lines between the BeagleBone and the MCU for further communication.
If you're wanting to experiment with your own Arduino-compatible circuits, then you'll need a an ATmega328P MCUs with Arduino Uno bootloader:
This is the same Atmel AVR ATmega328P microcontroller used in the official Arduino Uno, as well as our Eleven, EtherTen, USBDroid, and other boards. Perfect for building your own Arduino-compatible project directly on a breadboard or on a custom PCB, or for replacing the MCU in an existing board. Comes with the Arduino Uno bootloader pre-installed. Better still, it even has a special label stuck on top with details of the pinout, so you don't even need to look up the datasheet when connecting it up in your project! For more information and to order, click here!