> 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.

Multiplexing them in a "grid" arrangement (as others have
suggested) is probably the way that requires the least hardware.
Just a couple of transistors and resistors. A PIC I/O pin can
certainly supply enough current for an LED, but you still need to
be sure that the combined current for the max number of
simultaneous lit LED's doesn't exceed the rated current for a
port, or for the entire chip.  From the standpoint of software
overhead, a shift register would be about the easiest way to do
it. Just store the state of the LED's in a register (or two), and
shift out the contents whenever something changes. But then you
have to worry that the shift register chip can supply enough
current. Maybe could use super bright LEDs so you could get away
with less current. Micrel makes a couple of LED driver chips that
are basically just big shift registers with 15mA per pin
capability. One has 34 outputs and the other has 35. These also
provide current limiting so that you don't need a resistor for
each LED and can control the brightness of all LED's together.
Could also use it to control other things besides LED's, like
relays. Nifty chip, but may be hard to get. I had a few samples
of them several years ago.

Another idea is to use a 74hc138 to turn on any one of 8 LED's
using only 3 I/O pins. If you need more than one LED at a time,
you could multiplex using software, though it might be pretty dim
since each LED would only be on 1/8 of the time, so you would
probably want to use as much current as the chip can safely
supply. Two 74hc138's could select one of 16 LED's using 4 I/O
pins.

The 4017 that someone suggested was a pretty clever idea. That
could also be used to create a very large multiplexed array using
only a few PIC pins. For example, you could have a 6 X 10 array
using 8 I/O pins, but again it might be dim because of the low
duty cycle.


---
                                        Peace,
                                        William Kitchen

The future is ours to create.