gardenyu wrote:

> I'm building a 3 digit LCD display trying to use a Microchip's AY0438
> controller. I read the C18 compiler library and found there are some
> pretty good library functions for Hitachi HD44780 LCD controller.
> This is weird to me. Why do they write library functions for a driver
> which is not even their own product? I also noticed there are a lot
> samples everywhere for driving the Hitachi chip, and very few on
> AY0438 driver. It turns out for a starter, it is much easier to use a
> much more expensive chip (80 pin for Hitachi) to realize a very
> simple function.

Forgive me if this is stuff you already know but since you are comparing
the two it sounds like you haven't driven LCDs directly before.

The AY0438 is meant to drive LCDs with a single common(or maybe two or
three but roll your own common drivers). You can't drive a lot of
segments with those but the contrast is great and you can use them over
a wide temperature and voltage range.

The HD44780 is typically used heavily multiplexed with displays having
lots of commons so you can drive many segments. I have never used the
chip by itself, I've always bought a display that already incorporates
one on it. They are the most popular LCD driver chip and very very old.
But not obsolete.

If you decide you want to use an LCD with one to four commons I would
suggest looking at a microcontroller that already has an LCD drive
peripheral inside. Microchip makes some, although I've never used them.

The easiest way to get familiar with direct LCD drive might be the AVR
Butterfly board, Digikey has them for $20.

TI's MSP430F4xx series microcontrollers also have LCD drivers inside and
they are awesome chips.

Cheerful regards,

Bob
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