LED Life and Charlieplexing


Yesterday, we featured [Andrew]’s orientation aware camera. We want to highlight another one of his projects: LED Life. It’s a 6×5 LED matrix playing Conway’s Game of Life. He used the low power MSP430 like our e-paper clock. The best part of the writeup is his explanation of how Charlieplexing works. Microcontroller GPIO pins generally have three possible states: output high, output low, and input. This combined with the directional nature LEDs and some creative wiring means you can run a large matrix of individually addressable LEDs with just a few IO pins. Instead of just flipping the IO pins on and off you change their assigned state. Have a look at [Andrew]’s site for some great illustrations of how the system works. A video of his LED Life board is embedded below.

7 thoughts on “LED Life and Charlieplexing

  1. Thats a really interesting way to use the GPIO of a MCU. I would have never thought to utilize the input state to control an output.

  2. This charlieplexing is very interesting, only drawback seems to be that he only turns on one LED at a time. Of course (he mentions it) he could lit up more than one at a time, but probably this will soon draw too much power. Amplifier stage would be necessary then (and a more complex one than for normal matrix multiplexing), killing the simplicity of the design.

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