> Thanks, that's a start, but not quite what I had in mind...looking for a PIC
> or similar microcontroller-driven set of multiplexed LEDs to allow roughly a
> 7 x 80 pixel field to be controlled.  Perhaps use a Hitachi LCD display and
> a few buttons for operator interface.  Any other suggestions will be greatly
> appreciated.

How big do you want it?  The HCMS 2975 has a 7*80 field :-)  I asked about
this earlier on the list, with no response so far.

But seriously, you might want to build your display the way they did.  A
320 bit shift register, with some latches.  Serially clock your data into
the shift register, then latch the display.  Shifting 5*7=35 bits and then
latching will cause the display to scroll.

The problem I'm running into with my displays (and I believe all my problems
are now related) is that current surges from the LEDs are causing my PIC to
brown out.  <sigh> HP recommends splitting the supplies, but when you have
pins like:
        Vled
        Vlogic
        GND

on the smaller displays, I have no idea how to wire them up without causing
ground loops.  Surely HP wasn't asking me to connect the grounds of two
different supplies together.  Perhaps they were...

Returning to our original subject, consider using separate supplies.

Jon Doran