Another way to look at Charlieplexing


Charlieplexing is a technique that allows you to drive a larger number of LEDs than wouldn’t be possible with the same number of I/O pins on a traditional multiplexed matrix. If we lost you there just think of it as lots of blinky lights connected to a small number of pins. It works by leveraging the one-way nature of a diode. Current will only flow through an LED in one direction so if you hook up your display in a clever way you can drive multiple LEDs from one I/O by switching the polarity of that pin between voltage and ground. [M.Rule] recently looked at using Charlieplexing with LED modules. His conceptual approach to the problem is different from those we remember seeing before and it’s worth a look.

Instead of just using the formula to calculate how many LEDs he can drive [M.Rule] is using a table of I/O pins to establish how many and in what order these displays can be connected. Each colored set of blocks represents an LED module. The graphic above shows how 18-pin can be utilized. He even filled in the unused pin combinations with input buttons.


  1. brian says:

    Great writeup! Detailed, good figures, easy to understand. All writeups should strive to have the same quality as this one. Plus who doesn’t love the blinkenlights ;)

  2. Bogdan says:

    This is really brilliant work!

    Except that, at hobby level, i would always prefer to make a tiny board with shift registers+driver on each led array. Then all boards connect with 6 wires.

  3. Where is a good place for a tutorial on this? I’d like to make a big audio visualizer display in my new house (one day if I can stop buying every electronic along the way). What are some other good electronic projects places as I trying to learn more by building, seems to make more sense to me that way.


  4. static says:

    Far out, thanks for directing us to this.

  5. says:

    His posts make you wonder how Szczys ever learned how to spell his last name.

  6. Wolfy says:

    “… than would be possible…”

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