First of all, do you know what this “Charlieplexing” is? It is an electronics techniques, which developed by Charlie Allen, a genius and talented engineer at Maxim.

According to Charlieplexing theory, it’s involved minimizing the use of I/O pins on a microcontroller to drive a maximum number of LEDs. In addition, the n drive pins can be used to drive n digits with the n-1 segment. This also means, the n drives can be used to control the n²-n LEDs!

Charlieplexing can easily drive a seven-segment display of up to 9 digits with the 9 I/O pins; while the standard multiplexed display will need at least 17 I/O pins to drive the same display. This shows that Charlieplexing is more efficiency than the multiplexed display.

The Maxim defined the Charlieplexing as “a display driver circuit to reduce pin-count”. This multiplexing method is used in their own LED display drivers. By using the Charlieplexing, you can apply the fancy dot matrix or clock display easily without even need to use many components!

By the way, create a Minidot 2 clock for yourself with this Charlieplexing method, would be a fascinating stuff that you’ve ever make before. Go on and try it now! [read]

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