1) I used my PC's +5V line (the RED line!) for the +5v source for the LCD - IN CONJUNCTION WITH A 100-OHM RESISTOR! The controller chip got a little too hot for my comfort without this resistor. The power for my LCD runs through a standard DB-25 Male to Female connector (15') in my car which adds a bit of resistance itself. Be forwarned, some LCDs may burn up without a resistor!
2) Some LCDs require NEGATIVE voltage for contrast, while others need POSITIVE. Use a 10K - 100K potentiometer (rheostat/taper) for the contrast. Connect -5V to the left terminal, +5v to the right terminal, and pin 3 on the LCD to the center (variable) terminal. My LCD requires negative voltage to display anything, my friend's is close to ground. This is a sure-fire way to make it work. Note: -5V can be tapped from pin #4 on the com/serial port (use a 1K resistor).
3) Pins 1 and 5 on the LCD connect directly to ground. Ground can be sourced from either the black wires (any black wire) from your PC's power supply, or from any pin on the LPT between 18 and 25 (inclusive). Many people tie 18-25 together and to the ground but this is not needed - they are already grounded in your PC's motherboard. Thus ground can be gotten from any of these (I still used the black wire on the molex connector I got my +5v from to reduce clutter on my DB25 connector).
4) All green lines are data lines. The numbers in ()'s indicate where they go to on the LPT port (example: DB4 (6), connected to LCD pin 11, goes to the LPT pin #6. FYI: Radio Shack's DB25 connectors are labeled with these numbers, as are most connectors on the rear of PCs.
5) Pins 4 and 6 on the LCD are directly connected to the LPT (17 and 1, respectively) but are also tapped into the +5v line with 10K resistors. Use TWO resistors as pictured.
6) If your LCD is >2 lines, you may need to connect some lines differently. This works for any LCD of X chars by 1 or 2 lines with a Hitachi chip. I am not 100% sure on the differences but I believe that it's #6 on the LCD, enable, going to LPT 17 instead of 1, and 4 on the LCD, RS, going to LPT 16.
I cannot promise that this LCD schematic will work with any software other than the listed software. I know that this works for me and I know others whom it works for as well.
A few notes on the PC diagram:
To make setup and removal as simple as possible, I did the following:
1) I cut 10 wires from old christmas lights, each 18" in lengh. Since the wire was twisted-pair (it was actually twisted-triplet, I just took the light wire off), I used 5 pairs. I connected them to pins 1-9 and pin 17 on a male DB25 connector, and then connected the other end to the corresponding pin on another male DB25 connector, with the exception of running wire #17 from the PC to #10 on the second male connector.
2) I then ran the +5V to pin #23 on the second male DB25 connector, ground to the 24th, and -5V to pin #25. I used 12" of the double-stranded wire inside a molex connector (removing the pins and re-crimping the wires to the appropriate pins, with a 100-ohm resistor in series with the +5V line). This allows it to be "unclipped" from the PC. I used 18" of the wire connected to a 1k-ohm resistor, which was then connected to the 4th pin on the COM port, for the -5V (pin 25). On the LCD end, I connected a female DB25 connector to the appropriate pins on the LCD and the -5V to one end of the 10K potentiometer. Follow the schematic on the LCD page for more information. You will be using 13 out of 25 pins, meaning 12 can be used for a backlight on the LCD if it has one, and even the keyboard/keypad connection.
Doing this allows you to have a very simplified, and easy-to-troubleshoot wire setup. The LCD end was all contained behind the LCD in a custom-made plexiglass enclosure. The female end on the LCD was connected to the male end of the DB25 cable. The DB25 cable runs from my center "Console" to my trunk, where the female end is plugged into the (second) male DB25 connector.
PC molex connector:
=========
/ Y B B R \
============
Y = 12V (not used)
B = GND (both = gnd, same source! You can also use the PC's chassis as ground)
R = 5V
