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LCD Display:

I didn't have room for a full VGA display, but definately wanted to see what songs were playing as well as possibly having feedback when searching for what song or playlist to play next. With this LCD character display and the Winamp plug-in, I can at least list the MP3 ID3 tags for the currently playing track. Perhaps if I change from Winamp to CAJUN, or some other program, I'll have more interaction with the LCD display, but for now, song information is fine.

The LCD display that I've chosen is a Seiko L4034 40x4 LED backlighted character LCD display. I can display four lines of text, each being 40 characters wide. Considering that the longest MP3 ID3 title can be a maximum of 30 characters long, I definately didn't want to get a 20x4 display. Since I drive at night, backlighting was a requirement.

This LCD display uses the popular HD44780 controller chip (actually two of them - each controlling 40x2), so it is fairly easy to find programs that interface with it. Two Winamp plug-ins, Michael Lynch's LCDisplayer and Nathan Stuart's WinLCD are both compatible with it, as well as CAJUN and some other MP3 programs. Many LCD character displays use this controller chip, and they are usually interfaced through the parallel port. The other common standard that I have seen uses a serial interface and has a built-in keypad controller which may be useful for some users. Matrix Orbital and Crystal Fontz make these types of displays.

I found my LCD display at eio.com for only $20, so it was a pretty easy choice. EL (electro-luminescent) backlighting would be neat, but it needs an inverter for AC power, adding cost. EL backlight displays often have a cool blue background, while the LED ones usually have a yellow/green or perhaps an amber color to the backlight. In the daylight, mine looks green. At night, it glows yellow/green. See the pictures below to see the specific colors.

This LCD display runs off of the parallel port. Since I have my infrared remote control running from a serial port, and at some point may put an automatic power on/off device onto the other serial port, I really needed a parallel port LCD display since I only have two serial ports. The wiring isn't trivial, but can be done with some patience. Here is the wiring schematic for Seiko's 40x4 character displays:

Seiko LCD to parallel port wiring diagram

NOTE: The wiring schematic shown on eio.com's webpage is wrong! It shows wires 10 and 11 transposed in the diagram, although the table is correct.

This LED backlight requires a +5V power source, so I just ran wires from a standard 4-pin Molex hard drive connector to the back of my custom computer case. I put a set of spring-loaded speaker connectors to the back of the case, and just run wires from there up to the dash where the LCD is mounted to get my 5V to power it. All other signals run from the parallel port. As the wiring diagram shows, there are two potentiometers that control the contrast adjustment for the LCD display, and the LED backlight brightness. Radio Shack didn't have the particular potentiometers that I wanted in a small size, so I got some micro-pots from a local electronics store, Cumberland Electronics.

While my prototype circuit works, I want things more compact and neat, as well as more reliable. To this end, I've designed a mini PCB that has a 18-pin header and a 25-pin D-subminiature header to connect the 18-pin LCD display unit interface to parallel port via a 25-pin straight-through printer extension cable. This PCB has provisions for mounting both potentiometers and a 2-pin power header for ground and the required +5V power. I'm waiting for the PCBs to be made, but here is the diagram showing the wiring details, as well as a DXF file of the PCB design if you think you can get one made yourself:

Seiko LCD to parallel port PCB design

Problem: About my only real problem with the entire system is that I have a certain amount of LCD display corruption. I have fiddled with the timing sections in both LCD Winamp plug-ins, as well as all of the various parallel port options (EPP, ECP, DMA, IRQ, etc.) in my BIOS. Neither of these things helped. I tried a shorter parallel cable, about six feet long, as a test and that didn't have any affect. The top two lines of the display are much better than the bottom two. They normally work correctly, but the bottom two sometimes display strange characters. The most common issue is when I have the song title centered, there is sometimes two occurences of the text. One is left-justified and overlaps itself in the center of the display. The bottom line often gets extra or misplaced characters. One odd thing, which is strangely consistent, happens when the last character on the second line is a ")". When this happens, the last two lines get completely non-readable with random characters for a few seconds or minutes, and then those two lines of garbled text often disappear, leaving only the two top lines showing. I have a second LCD display unit, and it does the same thing, so the unit itself isn't faulty.

Update: I've solved the problem that I was having with LCD display corruption. The latest versions of Michael Lynch's LCDisplayer plug-in for Winamp, versions .60 beta and newer, offer greater compatibility and tuning parameters for parallel port timings. These new parameters, along with more detailed documentation, allowed me to adjust my settings to work correctly with what I thought was a standard ECP parallel port. I thought that since it was a new motherboard, it wouldn't have any problems, but apparently I was wrong. I have to use the "Alternate Fast" compatibility mode and tweak the control and data delay values according to my processor speed. The good news is that it seems to work about as fast as the regular fully-automatic mode, but without the display corruption. Get the latest version of the plug-in, version 1.00, since it offers these changes as well as some nice additions.

These settings in my LCDisplayer vis_LCDisp.ini file work for my problematic LCD display: 

  [LCD]
  Port=378
  OpenMode=1
  Compatibility=3
  ControlDelay=2
  DataDelay=1900
  ShowInit=0

Hover over each thumbnail image for a brief description of the picture, and click the thumbnail image to open the full-size picture in a seperate window.

LCD before soldering LCD with 18-pin header soldered on LCD with 18-pin header soldered on

Bottom of LCD after soldering Prototype circuit for connecting LCD to parallel port and power LCD with black electrical tape covering the green PCB. Simple way to make it match the dark color of my dash bezel.

LCD wiring showing prototype connections to parallel port Dark closeup of LCD showing LED backlight color and original text layout Closeup of final LCD display unit custom mounted in the dash with and final text layout

LCD mounted in truck dash - daytime display LCD mounted in truck dash - night display showing backlight Completed installation showing LCD mounted in truck dash


This page was last updated on Friday, February 8, 2002

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