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Re: using character LCD as display.

Thr original chipset is Hitachi HD44780 from memory - I have all the datasheets and interfacing schematics for PC parallel port at home which I can retrieve later this week for anyone who is interested. It shouldn't be hard to find these on the net though.

Interesting point #72: Character displays come in all shapes and sizes, 16x2, 20x2, 24x2, 16x4, 20x4, 40x4 (characters x lines) etc... All the displays except 40x4 use a single HD44780 controller. The 40x4 uses two HD44780 controllers. Because the PC parallel port has 3 outward control lines in SPP mode its possible to connect 3 displays to the same parallel port in 4 or 8 bit mode (with their data lines in parallel) and control them all simultaneously (with different data of course). The programming for single or multiple displays is ridiculously simple and easily determined from the datasheet. I might even have some sample code.

If you are experimenting with these make sure your parallel port is set to SPP (standard) in the bios, as ECP or EPP modes will cause you grief. Also when you are wiring the displays to the port it might be a good idea to use one on an ISA card because if you get the wiring wrong or something touches and you get a short-circuit the onboard parallel ports or laptop ports both like to burn and die.

Kind Regards,

Nick Bingham

----- Original Message -----
From: "Brian Empey, P.Eng." <>
Date: Wednesday, March 19, 2003 5:27 am
Subject: Re: using character LCD as display.

> Character displays have a parallel interface (they all use clones 
> of a
> Hitachi controller developed 20+ years ago).
> 
> You can use 8 or 4 data bits, there is one address line (command/data)
> one direction line (read/write) And a data strobe.
> 
> It is VERY easy to interface these to a printer port.
> The READ function is only used to poll the busy status, so you can tie
> it to WRITE mode, use only 4 data bits, and connect the 
> address/registerline to another data line.
> Thus, with 5 data lines and the printer STROBE going to the LCD STROBE
> you have connected the LCD to any device with a parallel printer
> interface.
> Just be sure to add a delay between characters since you can't 
> read the
> busy signal.
> 
> I did this back in the 80's ... probably have the code on 5" floppy
> somewhere........
> 
> Any device with serial or USB has an additional circuit board in there
> for translating (which will add to the cost).
> A 2x16 large character (1/2") STN with backlight and wide-temp range
> should cost you US$10- or less in low volume (under 1k pieces).
> A similar display in TN, normal temp, no BL is about U$5.50
> (STN LCD is higher contrast than TN -- [super-]twisted nematic liquid
> crystal display)
> 
> Brian
> 
> PS: NO, you cannot connect your VGA signal to a character display.
> Sorry.
> 
> Asher wrote:
> > 
> > "Jeremy" wrote:
> > >Has anyone out there used a Character LCD as a display.
> > >
> > >Anyway I was looking at something like:
> > >http://www.matrixorbital.com/products/lcd4041.htm
> > >could be put in a project box and strapped to my arm for
> > >travel.
> > 
> > I've used some similiar displays from Scott Edwards Electronics 
> [1] for
> > projects at work and they work well.
> > 
> > >I do a lot of hiking and am working on a hiking website...
> > >just thought a wearable could help me take notes and
> > >keep track of way points, etc etc.
> > >
> > >the LCD has a serial interface... anyone ever concert
> > >VGA to serial?
> > 
> > This'd be really tricky, you'd need a system running OCR software
> > looking at the VGA video! Far easier to design your user interface
> > device so that it can be hung off a standard serial port - the 
> serial> display can be directly connected, and it's pretty trivial 
> to make a
> > simple keyboard that can transmit serial data. Then you'd just 
> need a
> > suitably tweaked termcap entry and getty or similar running on the
> > serial port.
> > 
> > Asher.
> > 
> > [1] http://www.seetron.com/
> > 
> > --
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> -- 
> 
> Brian
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~
>  Brian Empey, P. Eng.
>      President
> 
> Technical Solutions Inc.
> Unit #1 7157 Honeyman St
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