Hello Mark and Jai!

On Thu, 27 Mar 2003, Jai Dhar wrote:

> IF you mean she has 100 LED's to control, she will not be able to do it
> easy with an F84. You first of all need more output lines, and you will
> have to use shift registers to do so.

[snip]

> 8 Shift register's will be able to control 8 bits each, so that is 64
> bits in total. IF she is using a matrix style display (which I hope she
> is), then this will be ok since you will need only 25 lines... but if it
> is 1 pin per LED, then you might be better off with a PIC that can
> handle more IO.
>
> Quoting MarkIsrael@AOL.COM:
>
> > Please forgive this absolute dumb newbie question.

I feel foolish having also just asked one myself, but a little better
answering one that I also just answered within about the last 72 hrs. :)
After a while the solutions all become second nature.

> > I have a correspondent who is trying to control a
> > 20-by-5 LED display with a 16F84 PIC.  She can make
> > 8 lights flash by writing to PORTB (she's sent me
> > her C code, which is quite similar to what's at
> > <A
> > HREF="http://www-
> ee.eng.hawaii.edu/~sasaki/EE361/Fall01/quickovp.pdf">http://www-
> ee.eng.hawaii.edu/~sasaki/EE361/Fall01/quickovp.pdf</A>
> > ),
> > but how can she write to the rest of the display?

Jai, 'more pins' are not necessary because the SRs are cascadeable.

Mark see http://www.piclist.com and in the FAQ search box right there
enter port expander or hc595. That's nicest because it's clearable and
latchable.

Doesn't even need to use the whole PORTB on the segments as described in
that pdf, just add another SR.

Have a :) day!

jb

--
jim barchuk
jb@jbarchuk.com

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