http://jp.ic-on-line.cn/IOL/viewpdf/MM5450_246958.htm

Say goodbye to Multiplex, Charlieplex. Here comes a new challenger.

Charlieplexing is a technique proposed in early 1995 by Charlie Allen at Maxim Integrated Products 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 utilizes the tri-state logic capabilities of microcontrollers in order to gain efficiency over traditional multiplexing. Although it is more efficient in its use of IO, there are issues that cause it to be more complicated to design and render it impractical for larger displays. These issues include duty cycle, current requirements and the forward voltages of the LEDs.


source: http://en.wikipedia.org/wiki/Charlieplex

Arduino Charlieplex

It is created to help make readable charlieplex code. It hides the pinMode, and digitalWrite calls for the user.