Imagine an 8x8 matrix of LEDs connected to an 8-bit port (with 8 suitable
R's).
To light one LED you make the two appropriate pins high and low, and all
other pins tri-state (input). The single LED will light up, and no other.
This is always possible, unless the two pins would happen to be the same
pin,
so in practice you can handle 8x7 LEDs with 8 pins.
This might sound a little cryptic, but try to draw it and you should
understand it.
It might even be possible to handle 8x7x2=112 LEDs by putting LEDs
anti-parallel. But beware of the PIcs current limits...
Wouter.

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From: Vernon Bradshaw <WVBradshaw@WORLDNET.ATT.NET>
To: PICLIST@MITVMA.MIT.EDU
Subject: More than 8 LED's from a single 8-bit port
Date: Friday, January 07, 2000 02:58

Is there a way to illuminate more than 8 LED's using a single 8-bit port.
I am tryin to have a block of ten LED's increase or decrease by one when I
press either an up or down button.

Thanks,

Vern Bradshaw
WVBradshaw@worldnet.att.net