> Now, how does one controls one of those displays? How complex will it be?
> Will a pic do the job? Do I need external electronics?

I only have experience with one type of graphical LCD, which was
controlled by a T6963C, and was very happy with it. It needs around 11
I/O pins (8 for data, 3 for control signals. You could eliminate a pin
by putting an inverter between READ and WRITE and you might want to
add pins for the FONT SELECT and RESET pins, though don't need to).
Electrically most graphical LCDs will require a negative voltage. I
created that using th ICL7660, but I'm pretty sure you can program a
PIC to control a charge pump, in which case you'd only need 1-2
capacitors, and an additional I/O pin. You will also need a
potentiometer to control the contrast (10-20 kOhm, generally), and
sufficient power if you're going to use the backlight (mine drew 960
mA, so use a 7805 instead of a 78L05).

The T6963C has a big advantage over other LCD display controllers
(like the Hitachi HD61202) in that it has a built in font generator,
which means you don't have to program your own fonts (especially
initially, when debugging the system, this is VERY convenient).
Another advantage of using a T6963C over other LCD controllers is that
most T6963C controlled LCD displays have additional RAM memory on
board, that you can use to store and retrieve data. This greatly
expands the things you can do with your PICmicro (I got at least 4 KB
more RAM than needed to power the display). This memory can also be
used to "double buffer" your display, allowing effects like fine
scrolling and fluent animation.

Of course, there might be other controllers out there that have these
same advantages, this is just my experience with this one system.

A disadvantage of the T6963C is that it has no guarantee to the time
it takes to complete an operation. Usually they are pretty fast (5us
or so) but nowhere in the specification it states that it won't wait
for seconds before returning control. I understood that some other
controllers do have guaranteed times, which has two advantages: 1) you
don't have to program time outs, 2) you don't have to read from the
display, as you know that after a certain time the operation is
complete anyway.

I would not recommend controlling an LCD display directly from the
PICmicro. It is possible, but there are many issues that can be easily
avoided by using an existing controller, and generally these don't
make the LCD much more expensive.

Greetings,
Maarten Hofman.

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