Product Review: Charlieplexed SparkFun 8×7 LED Array

abccharlieplexedledsanimatedI recently picked up the new SparkFun LED Array – 8×7 to try out some hardcore charlieplexing, and so far it’s been working great.

Quoting Wikipedia, charlieplexing is

“…a technique for driving a multiplexed display in which relatively few I/O pins on a microcontroller are used to drive an array of LEDs. The method uses the tri-state logic capabilities of microcontrollers in order to gain efficiency over traditional multiplexing.”

Charlieplexing itself is a simple idea and can be an extremely efficient way of making an LED grid. However, laying out the wiring of a charlieplexed grid, whether on a breadboard or a PCB, can be complicated and require a bit of thinking. It’s easy to layout a grid with 12 or 20 LEDs, but once you start trying to make grids with 30 or more LEDs, it gets a little crazy.

I love SparkFun’s 8×7 LED Array because it eliminates the need to go through the long process of designing and wiring together the grid. Plus it’s in a neat compact module that can be easily embedded. Out of the box, all I had to do was solder on headers and plug it directly into the digital pins on my Arduino. I didn’t need to wire any external resistors, as they’re already built into the board.100_5200

SparkFun has made an Arduino library for controlling the array that allows you to easily write text and draw shapes and do other interesting things on the grid. However, I wanted to use my array with my Raspberry Pi’s GPIO for the purpose of making an archaic internet-connected game system. I’ve written a single-file class in Python 3 for controlling the array with the Raspberry Pi’s GPIO, called pythonic-charlie, and you can find it here (my first legit GitHub repo! Woot woot!). It’s still under development, and still has bugs that need smoothing, but it allows you to display a list of coordinates, test the grid to verify that it’s wired properly, and display a neat little screensaver. I’m currently working on something that will display text. example-wiring

If you ever wanted to learn how to charlieplex LEDs, SparkFun’s 8×7 LED Array is a really great place to start.

smilefrowncharlieplexedledarrayanimation

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