LCD unit connected and working, currently showing MP3 song information on the LCD.
LCD unit connected and working, currently showing MP3 song information on the LCD.

This very simple module is driven purely by a computer parallel (printer) port. Almost no external components are needed; a few capacitors for voltage stabilization, a trimmer for the contrast adjustment and a resistor for the LED back-light. All communication is done directly over the parallel port data lines. The LCD is powered by an external 5 V power supply. It can’t be placed too far from the computer though since the recommended max length of a parallel cable is 15 ft.

Table of content

Software

Screenshot of LCD Smartie showing MP3 song information from Winamp.
Screenshot of LCD Smartie showing MP3 song information from Winamp.
Screenshot of LCD Smartie showing temperature values from some of my temperature loggers.
Screenshot of LCD Smartie showing temperature values from some of my temperature loggers.

I used LCD Smartie to drive and control the display. Things like MP3 song information, system temperatures etc. are available right out of the box. And they have a number of plugins available. If you want to show some custom data you can write it to text files and have LCD Smartie read and display the content of those files. It’s even able to cycle though a list of screens to show multiple pages of information, very cool.

LCD I/O

LCD pin Name Description Centronics pin DB25 pin
1 Vss GND 19 30 18 25
2 Vcc 5V
3 VLc Contrast (to a 10k variable resistor)
4 RS Register Select 31 16
5 R/W Read/Write (to GND)
6 E Enable 1 1
7 D0 Data 2 2
8 D1 Data 3 3
9 D2 Data 4 4
10 D3 Data 5 5
11 D4 Data 6 6
12 D5 Data 7 7
13 D6 Data 8 8
14 D7 Data 9 9
15 VB+ Backlight (120 ohm to 5V)
16 VB- Backlight (to GND)

Please leave a comment or tweet if you have any questions or feedback on this project.

Schematic drawing

Schematic drawing of an LCD connected to a parallel (printer) port.
Schematic drawing of an LCD connected to a parallel (printer) port.

Image gallery

Parts list

External links

Project: LCD unit driven by a computer parallel port by Thomas Jensen is licensed under CC BY-SA 4.0 with attribution required.

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  •   Created Nov 25, 2007
  •   Last modified 3 months ago

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