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/**
\file blink-charlieplex.dox
\page blink_charlieplex Charlieplexing Example

<a href="http://en.wikipedia.org/wiki/Charlieplexing">Charlieplexing</a>
is a technique for multiplexing large numbers of LED's on a small
number of microcontroller output pins.  LED's are arranged in
complementary pairs and managed by the Charlieplex class.  For this
example we are going to use 3 output pins to drive 6 LED's:

\image html charlieplexeg.png

The technique can be expanded to even larger numbers of LED's.
See the documentation for the Charlieplex class for a description of
how to connect up larger numbers of pins in a Charlieplexed arrangement.

The first step is to initialize a Charlieplex object with the output
pins it needs to drive:

\dontinclude BlinkLED/examples/Charlieplex/Charlieplex.ino
\skip #include
\until charlie

Then in <tt>setup()</tt> we use Charlieplex::setLed() and
Charlieplex::setPwmLed() to set three of the six LED's to
the desired output values:

\dontinclude BlinkLED/examples/Charlieplex/Charlieplex.ino
\skip setup
\until }

Charlieplexing can only light a single LED at a time.  It is therefore
necessary to constantly scan the entire LED array, alternatively turning
LED's on and off.  The user's peristence of vision fills in the gaps.
To do this, we call Charlieplex::loop():

\dontinclude BlinkLED/examples/Charlieplex/Charlieplex.ino
\skip loop
\until }

The downside of Charlieplexing is that when multiple LED's are lit, each LED
will appear to be dimmer than if only a single LED was lit.  This can be
counteracted by using brighter LED's or smaller resistors.  The danger with
smaller resistors is that if the program crashes or locks up for some reason,
a large amount of continuous current could be fed through a single LED and
cause it to exceed its maximum rating and burn out.

The full source code for the example follows:

\include BlinkLED/examples/Charlieplex/Charlieplex.ino

A more complex example that performs a LED chase over the 6 LED's follows:

\include BlinkLED/examples/CharlieplexChase/CharlieplexChase.ino
*/