Here's an interesting (and somewhat PIC-based) situation;
A customer has a requirement for a product that would have
an array of bicolor LEDs, the kind with two leads. Since the
necessary states of each LED include Off as well as red
and green, the obvious but messy way to drive them involves
connecting each LED lead to an output port. I.E. each LED
uses up two outputs.  This works great for just a few LEDs
but uses up port pins really fast!  We're talking some 50 or so
LEDs here.  :-(

One variation I thought of would be to connect one side of
each LED to a source of V+/2 and then tristate the output
to get the Off condition.  Better, but it still uses too many
i/o pins.  The code needed to do mutliplexing for power
reduction is a little scary too, but that can be dealt with.

Can anyone suggest a way to further reduce the i/o pin count
by some sort of clever matrix connection?  My poor tired brain
is just drawing a blank on this.

Brian Aase

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