RE: AW: [avr-chat] LCD duty cycles, help please

[Rune Christensen]

Hello

On LCD with the HD44780 the contrast is changed by a 10k ohm potentiometer.
The same could be done here but I don't know the exact values. 

I think you need to create some kind of controller for the LCD. It could be
a microcontroller. You need precise timing and if it going to be used as a
graphical display you will need about 640*480/8 = 38400 bytes of dual port
memory.

/Rune


> -----Original Message-----
> From: James Dessart [mailto:address@hidden 
> Sent: Sunday, February 27, 2005 11:17 PM
> To: address@hidden
> Cc: address@hidden
> Subject: Re: AW: [avr-chat] LCD duty cycles, help please
> 
> 
> On Sun, 27 Feb 2005 21:25:52 +0100, Rune Christensen 
> <address@hidden> wrote:
> > The LCD is split into two sections upper and lower. That gives 240 
> > lines each and you will only be drawing one line in each 
> section for 
> > each step. That gives 1/240 and because of some speciel things the 
> > duty cycle is 1/242.
> 
> There's a timing diagram at 
> http://www.nyx.net/~jpurbric/lcd/timing.gif actually, very handy.
> 
> > The VLCD is a DC voltage that is constant. Just like the 5 volt for 
> > the circuit board. If you change the VLCD the contrast will change.
> 
> I was wondering about that. How would one adjust it? A potentiometer?
> 
> > How often do you need to update the display? Do you need to 
> use it to 
> > video or only to slow graphic/text?
> 
> I'm going to interface it to a Macintosh LC, an old 68020 Mac 
> running at 16 MHz. It's really just for fun and learning. :) 
> if the display is a little persistent and slow, that's 
> entirely fine. The motherboard's just sitting around doing 
> nothing anyway.
> 
> James
> 
---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 0508-4, 27-02-2005
Tested on: 27-02-2005 23:44:40
avast! - copyright (c) 1988-2004 ALWIL Software.
http://www.avast.com