Mauricio Jancic wrote:
> Hi,
> 
>             I'm going to need to use an LCD, a graphical one. I would like
> to know how to choose one. I know it's a big question. lets see.


Hi Mauricio,

I think Maarten's suggestions are extremely good. Let me give you some 
counter-information that may further enforce his points. I'm currently 
writing code to interface with a Varitronix 100X32 graphic LCD:

http://www.varitronix.com/catalog/glm1.html

It's based on the SED1520 controller - which is a really old part.

The biggest problem I'm having is that there is *no* documentation 
available for the display. When I finally managed to get through to a 
Varitronix FAE, they sent me a copy of the "data sheet" which 
unfortunately was devoid of any pertinent information. So I had to 
resort to Trial-and-Error to figure out how their device works. For 
example, there's no documentation describing the mapping between bits 
written to the SED1520 and pixels on the display. There's no 
documentation describing how the SED1520's should be initialized for 
this display. There's no documentation on the contrast voltage (other 
than it's maximum value). I could go on and on...

To make matters worse, the SED1520 data sheet appears to have been 
written by a junior engineer. I say junior because they've chosen to 
describe Vdd as "0V" and Vss as -5V. This is really obscure! Once you 
manage to get over that and sift through the data sheet, the only 
pertinent information you'll find is the page describing the SED1520 
commands. BTW, also make sure to get the "newer" data sheet and not the 
"older" one (there are no dates or version numbers on either - so good 
luck figuring which is which), because the earlier one was apparently a 
Korean to English translation by a non-native English speaker.

Since the SED1520 is ancient, it lacks some of the nice features of the 
T6963C. For example, there is no built in font or extra RAM for a 
display buffer. I'm using an 18f device to interface to the SED1520, and 
have plenty of room for both the font and display buffer. I've already 
written a script that can extract bit mapped LCD fonts, so I had no 
issue with that either.

The only reason to choose a SED1520 based graphic display over the 
T6963C based one is cost or particular features the display has to offer.

Scott
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