Yep, the shift register is the way to go it looks like.     Ordered some of
these shift registers yesterday.  You are right, I'll have 22 lines plus 1
or 2 for the backplane(s)  I think this LCD has 2 commons, but they are not
multiplexed.

I got hold of a scrap LCD from the mfr for development that is about the
right size and has about the right number of segments.  This will get me off
the ground until I can get  cu$tom prototype$ from them.

I'll use 3 pins from the pic, one for serial data, one to clock in the
serial data, and one to clock it out of the shift register all at once.
Trying to get this last clock to be very isosynchonous will be critical to
getting a long term DC level on the lcd.  I've been using a 9V battery to
decode my scrap LCD (a no-no! Don't try this at home!) to see how it ticks.
Shows how simple driving an LCD can really be!

Yes, I would like to see the code you've developed, might save me a little
time.

Lawrence


----- Original Message -----
From: "Dwayne Reid" <dwayner@PLANET.EON.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, November 30, 2000 6:42 PM
Subject: Re: [PIC]: Custom LCD's are a pain in the..... Ask me later


> At 08:33 AM 11/30/00 -0600, Lawrence Lile wrote:
> >Thanks,  Paul, I didn't even realize Philips was into LCD drivers!
> >
> >I may also experiment with Dwayne Reid's suggestion of using shift
> >registers.  I have to count pennies on this project.
>
> Give it a try - you might be surprised at how easy it is!  One thing I
> probably forgot to mention - you need 22 SR outputs to drive the
> segments.  One of the remaining 2 outputs will drive the back-plane,
> leaving you one output pin that you can do with as you please.  It takes 3
> pins to drive the SR chain and you can get back 2 of those pins as inputs.
>
> Theoretically, you could knock the PIC pin requirement down to 2 pins by
> coupling either the data line or the clock line to the latch input via a
RC
> delay.  Works great on the TPIC6x595 but the 74hc595 does not have schmitt
> trigger inputs and the latch edge is too slow to work reliably.
>
> I've got ugly code I could share - its ugly because of the amount of stuff
> I get a lowly 12c671 to do.  But it works and it is maintainable.
>
> dwayne
>

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