Hi all. I had an idea for driving a bi colour LED using only one pin. My
basic idea is to get one switch and one bi colour LED (basically 2 LEDs
back to back) to work over just 3 wires. Here is a pic of the remote end
of this (drawn by hand as Roman has taken his page down):

         (-|>-)bi colour LED   _=_ Switch
      ,--(    )--,------------o   o--,
      |  (-<|-)  |                   |
      |          |                   |
      |          |                   |
      |          |                   |
      O          O                   O
     1          2                   3


1= PIC Output
2= +2.5 Volt
3= PIC Input


Basically the idea is to float one end of the LED in the middle of the
PIC output range so that when I output a low, one LED is forward biased,
and when I output a high, the other LED is forward biased. If I want the
LEDs off, I'd tristate the pin.

So...will this work? I'd have to make sure the LEDs have a forward
voltage of under 2.5V I guess. What will happen with the input pin? What
will the PIC do with 2.5V on an input? Is that a high (because it is
greater that .8V)? The other question is will this work over a long
wire? Since the currents are so low, will line drop become a factor,
making the voltage too low to forward bias the LEDs? I guess the other
question is how to generate the 2.5V. Could I use a zener, or is there
such a thing as a 2.5V zener?

Thanks,

Josh

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