Can you use bi-color leds, and pulse between the two to get yellow, or must you
have three seperate colors per LED?

If you get a bi-color led (bargraph or seperate) I can see a simple routine
which would only need to be called 100 times a second or so(5-10 instructions,
maybe), and would give you 3 easy to read colors from the LEDs or bargraph.  It
would take 1 pin per LED, and 1 extra pin with a buffer (two transisters).

Hook up one side of each LED to a pin (say seven LEDs).  Connect the 8th pin
(control pin) to the other side of all the LEDs (using a buffer, one pin won't
handle all the current).

I'm not going to work out the code, but the idea is:
Every time the routine is called, COMF the port.
Every other time the routine is called, XORWF the port with the green led byte.
On the opposite cycle, XORWF the port with the red led byte.
(each cycle you are either XORWFing the green or the red bytes with the port)
Any bit which is NOT set in either the green or the red data bytes will be
either yellow, or off.  To set an LED yellow, set it's value to the opposite of
the control pin's value.  To turn an LED off, set its value to the control pin
value.

-Adam

Frank Adlam wrote:
>
> I need to build a LED bar with single tri-colour rectangular LEDs.  Red,
> green and orange will be fine but other combinations can also be used.  If
> the tri-colour LEDs comes in bargraph package it will be very helpful.
> Where do I find it?  Have surfed the web but did not get what I liked.
> Maybe you have used the tri-colour LEDs before in a project, where did you
> source it and who makes it?
>
> Any help will be appreciated.
>
> Thanks for your help.
> Frank Adlam