Yeap. Neat logic there!

John


--- "M. Adam Davis" <stienman@gmail.com> wrote:

> Since each LED on the bargraph is individually
> accessable (ie, both
> anode and cathode are separate from the other LED
> anodes and cathodes)
> then you can easily implement a multiplexing or
> charlieplexing scheme.
> 
> So you could drive 10 LEDs with 6 pins from the PIC:
> 1 pin goes to four of the LED cathodes (row 1)
> 1 pin goes to the other four led cathodes (row 2)
> 4 pins go to two anodes each (columns 1 through 4)
> 
> If you bring row 1 low, row two as input, then you
> can light any of
> the four LEDs on row one by bringing any of the
> columns high.
> 
> Then switch row 1 to input, bring low 2 low output,
> and do the same.
> 
> Swithc back and forth more than 30 times per second
> and users will see
> all the LEDs being operated at once.
> 
> Charlieplexing is a bit more complicated, but allows
> you to control 20
> LEDs from 5 pins, or 12 LEDs from 4 pins, etc:
>
http://www.instructables.com/id/ED0NCY0UVWEP287ISO/?ALLSTEPS
> 
> -Adam
> 
> On 4/19/07, Edward King
> <edwardcking2001@yahoo.co.uk> wrote:
> > Hi!
> >
> > This is my first post, so hello to everyone on the
> list...
> >
> > I need to run a bargraph display from a PIC (exact
> type to be decided, but I have a range of 16F and a
> couple of 18F devices lying around).
> > The trouble is that due to space constraints, Im
> not really able to squeeze a 40 pin device in to the
> assembly and I dont have many GPIO lines left
> over...
> >
> > So my intention was to use a serial to parallel
> shift register to give me the required outs from a
> couple of pins. Trouble is that it seems only 8 bit
> SRs are common now (and the level meters / bargraph
> displays are all 10 part) so I was wondering how
> other people have done this.
> >
> > I tried looking through the archives, but I
> couldnt find anything where the designer has adopted
> this approach.
> >
> > EK
> > --
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