From: Rich Webb
Subject: Re: Help: using (connecting) 4bit LCD on parallel port
Organization: Line Eater Memorial Fund
X-Newsreader: Forte Agent 1.92/32.570
Date: Sat, 16 Nov 2002 21:39:00 GMT
NNTP-Posting-Date: Sat, 16 Nov 2002 16:39:00 EST
On Sat, 16 Nov 2002 20:43:07 GMT, "Te" wrote:
>Let me start with- I'm not very technical, so if you can help, and are
>willing to help - I'll need any explanations in simple terms :) Also if you
>can, PLEASE PLEASE PLEASE email any response to me- I really want to make
>this work- and don't read the groups too often.
Then perhaps you'll not see the response but I prefer to answer public
questions in public.
>I purchased a 2x20 LCD display from bgmicro.com (the lcd1022), which has an
>equiv. controller to a hd44780. It has 10 pins connection pins (the link to
>a spec sheet is below), and from what I understood by the document on
>bgmicro's site, its a 4-bit interface (since its only using datalines 4-7
>only, and not 0-3). So by looking at a schematic for an 8bit lcd, I matched
>the pins from one lcd to the other (ie: vcc to vcc, d4 to d4, rw to rw, e to
>e, etc), and connected it to my parallel port. But all I'm getting is
>jibberish on the display :( I'm using a program called Smartie-LCD for
>display simple computer info (cpu temp, fan speed, etc)
From a quick look at the LCD Smartie page, it looks like it is written
to support 8-bit interfaces.
"Ok, i had some ppl from sweden who had 4 bit LCD's. One of them told me
that you could mod your 4 bit LCD to a 8 bit by soldering wires directly
to the chip. the codes next to the pins indicate tell you what wires you
can use in the above circuits Beware not to solder anything wrong!"
Interfacing to this type of display with only four bits is pretty
common. Basically, the module starts from power-on reset in 8-bit mode.
Wire the lower 4 bits to ground and command it via a little dance to go
into 4-bit mode -- which, conveniently enough, only requires you to use
the upper four bits. Using fewer pins is usually A Good Thing,
especially when interfacing to microcontrollers, which is why
nibble-wide modules are sold in addition to "regular" byte-wide.
There's no intrinsic reason why the software couldn't be written to
initialize and operate the display in 4-bit mode. However, until it is,
BTW, there's a copy of the Optrex manual available online at
Hang on to your 4-bit module (or trade it to another hobbyist) but
you'll need an 8-bit module to use with that application. Also, with
respect to the note above about soldering directly to the pins on the
controller -- be careful that the pins are not also connected to ground.
If you decide to go that route, you'll probably need to lift them from
the pads and solder directly to the pins.
Rich Webb Norfolk, VA