How many digits do you need? 

This is a scheme where if you want 7 segments only (not necessarily 0-9 only), 
you can get away with 8 outputs from the PIC, and this will allow you up to 8 
digits.  But you have to use a non-multiplexed 7-seg display (ie: individual 
digits).  I'll try to re-derive it here ...

For the first digits, PIC outputs 0 thru 6 go to segments a thru g on digit 1, 
and output 7 goes to the common for digit 1.  For digit 2, use output 6 as 
the common, and send the rest to the segments.  Digit 3 will use output 5 for 
the common.

To turn display a number on any digit, set the common line for that digit low 
(assuming a CC display), and the others are set to either high (segment on) 
or floating input (segment off).  Don't set it low for off, or it will turn 
on another digit.  Now, all you need is some fancy footwork in code and 
you're good to go.

Cheers,
-Neil.




On Sunday 11 September 2005 06:14 am, Mike Harrison scribbled:
> On Sun, 11 Sep 2005 01:39:34 -0700, you wrote:
> >I vaguely recall an optimization where you could get by with less
> >than 7 connections to an LED display if all you wanted was the
> >digits 0123456789, but I'm not finding it via search, and just
> >looking at the digits isn't helping...  It may have involved some
> >logic (segment x is always NOT segment y), in which case it's no
> >use to me, but the half-memory is driving me batty...
> >
> >Any ideas?
> >
> >BillW
>
> Don't think there's anything you can do short of BCD encoding if you need
> 0..9 For a more limited range, e.g. the first digit of a 24 hour clock,
> there are some obvious savings to be made.


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