Build your own LCD for your computer

If you want to have your own LCD to show anything you want on your computer, you could build, connect and interface it with your computer and forget about buying one.

Parts used:

LCD from a credit card reader.
Variable resistor from an old monitor.
25 pin conector from a printer cable.
The wire from a floppy disk to the mainboard.



At first when we at began this project, we didn't have any idea on how to control a LCD, what we were trying to do was connect someway the LCD to a battery and some LEDs and do the test and error technique to understant how did it work.

credit card reader
opening the credit card reader

We need a LCD so we search for one, luckly we found an old credit card reader device, like the ones used on shops, just unscrewed it and remove the LCD (Liquid Cristal Display) the pins were very long so it was easy to connect to a board.

We manage to connect a switch block also on the board and a variable resistor for the brigthness

Searching on the net we found a that the chips our LCD have was HD4478 compatible, so it seems HD4478 it's a standard an found lots of information about it, then we began to play with it with the switches, but we only could send the initialization sequence to obtain the cursor and send the A letter to it, it begins to repeat the letter because we didn't use a clock to send it and it was done manually. It was a first step and learn a lot about HD4478 brain. Later on, we took an old printer cable and tried to do the same thing but using the computer to send the commands instead the manual switches, then we would be able to control timing.

It was a success we have some experience controlling the parallel port because our robot arm Sicario. We coded a simple rutine to send the rigth numbers to the LCD pins so, we were able to send the name "" to the LCD.
It was time to program some kind of driver to controll it, but another search on the net show us that it have been done by someone else (Michael McLellan), so we just go to his website and follow the instruccions.

I suggest you to go to lcd-mod website and read all the information and the wiring schema if you plan to try it yourself.

The software is named: lcdmod and its a driver to controll the LCD from Linux, it creates a /dev/lcd device so you can send commands to it. It works very well and an example showing actual time is on the package.

Once installed you could send any word you wish with this command:

echo -en "Hello World" > /dev/lcd

if you want to clean the screen, this especial sequence have to be sent:

echo -en "\033[J\033[H" > /dev/lcd

If you have a temperature control program you could show it on the display, or your PC free memory or show you a message when certain event happens. I used to show me who is now looking at my website, it works by checking the Apache log and every 5 seconds show the last IP that was on the server. The script is this:

while true;
    echo -en "\033[J\033[H`tail -n 1 /var/log/httpd/access_log |cut -f 1 -d " "` \r\n`tail -c 17 /var/log/httpd/access_log`" > /dev/lcd
    sleep 5s

The last step was to integrate it inside the computer on a 5 1/4 bay, the wheel on the rigth is from a old VGA monitor and controlls the variable resistor for brightness.

It's nice for you case modding and it's better if you do it yourself, I can also say that we found other LCD HD4478 compatible on old devices like laser printers that can be used, the only difference may be the columns and rows you will have to work with, but this is a parameter that lcd-mod could control.


I leave you this links were we found all the information we need:

Frequently Asked Questions about LCD projectors, Videoconferencing, DTV, computer presentations and a/v equipment
EPE FAQs & Resources
LCD Intro
CrystalControl Beta Test
Graphic LCD Controller/Module Info
LCD Drivers and Controllers by DME Technologies
2-Wire PIC LCD Interface by Myke Predko
Fil's FAQ-Link-In Corner: LCD Technology FAQ
Computer display projects
Overclockers Australia - Build your own printer cable LCD Display
LCDproc - Home
LCD (44780.htm) to parallel port scheme and C source
How to control a HD44780-based Character-LCD
Displaying Real Time System information on a LCD Display using LCDproc & lcdmod LG #76
lcdmod wiring for HD44780

Feel free to post your comments or suggestions on our Linux Forum.

DrDoom at, Necro_ at, Klmar at contributed to this article.

by DrDoom