Computer LCD Display Project

for system information

LCD display

This little and fairly quick project is to provide a means of displaying information such as CPU, system and hard drive temperatures, fan speeds (maybe), drive usage, and other stuff like email waiting and local weather.


3rd September 2004
I will build one or more simple units for testing purposes using some LCD displays that I have in my "junk box" and a connection to the parallel port of my computer as this requires virtually no extra components. The software will consist of one or more programs freely available on the internet with tweaks for my particular purposes. This wealth of free software supports very well a homebrew approach to LCD displays as well as many of the commercially available units. LCDproc, LCD Studio, LCD Smartie. There is even an LCD plug-in for WinAmp.
Plus there is free software produced by many of the LCD module manufacturers for use with their units such as Crystal Control

After I decide exactly what I am looking for, I may well purchase one of the excellent Matrix Orbital LCD displays with USB interface such as the LK202-24-USB. These displays come with extra features such as general purpose outlets for control purposes and software (LCDC). USB is the preferred method of connection for me as I currently use only 3 or 4 of the 8 USB 2.0 ports (still 2 unused headers onboard) on my ASUS P4P800 Deluxe motherboard and I wish to continue using my parallel port for my printer. (recent note: I have bought a new Canon iP5000 printer and it only supports USB but I still use the old printer from time to time)
I have looked into building my own USB interfaced unit but this seems tricky and expensive which is a shame given that I have several LCD displays laying about.

HD44780-based LCD modules

Pin assignment

The following information on pin assignment is the industry standard for character based LCD modules with no more than 80 characters.
Make certain to check the datasheet to identify pin 1 before making any connections.

Pin number Symbol  Level   I/O Function
1 Vss - - Power supply (GND)
2 Vcc - - Power supply (+5V)
3 Vee - - Contrast adjust
4 RS 0/1 I Data/Instruction select
0 = Instruction input
1 = Data input
5 R/W 0/1 I Read/Write select
0 = Write to LCD
1 = Read from LCD
6 E 1, 1->0 I Enable signal
7 DB0 0/1 I/O Data bus line 0 (LSB)
8 DB1 0/1 I/O Data bus line 1
9 DB2 0/1 I/O Data bus line 2
10 DB3 0/1 I/O Data bus line 3
11 DB4 0/1 I/O Data bus line 4
12 DB5 0/1 I/O Data bus line 5
13 DB6 0/1 I/O Data bus line 6
14 DB7 0/1 I/O Data bus line 7 (MSB)
15 VB+ - - Backlight supply +ve
16 VB- - - Backlight supply -ve


6th October 2004
Well I constructed a test display unit using one of my "junk box" LCDs and other stuff from this same junk box using the circuit below.
reg circuit It was connected to the parallel port and to a USB port to provide a 5V supply for the display itself. Basically all I used was the display, a piece of ribbon cable with 25-pin D male plug, a partial USB extension lead (socket end had been removed for another project) and a 5Kohm linear potentiometer to adjust display contrast as I couldn't find a 10Kohm pot in my junk box. I also did not use the 100 ohm pot as my display did not have a backlight. Still it all worked OK but would much prefer a backlit display in the final setup.

I have no intention of putting this particular unit into my computer but it has shown me that I should be able to do what I want with such a display. I have decided to buy one of the Matrix Orbital LCD units I mentioned earlier when I can afford one (they are not the cheapest things in the world).




Stay tuned for more.
*** Note that all of this is done at your own risk and I accept no responsibilty if you blow something up or burn your house down.


Last modified: 27th March 2005