A. Connection diagram of a LCD module

This is the original description by Nils Färber from src/lcd/lcd/driver/README. I adjusted the drawing to clarify the short cut between terminals 5 and 1 on the LCD module.

--------------- snip -----------------

25 pole       LCD
SUB D         Panel    Pin
---------------------------
18-25         GND          --+
              GND      1   --+--- \ Connect to
              R/W      5   --+
              +5V      2   ------ / Gameport
1             EN       6
2             DB1      7
3             DB2      8
4             DB3      9
5             DB4      10
6             DB5      11
7             DB6      12
8             DB7      13
9             DB8      14
14            RS       4

Pin 3 on the LCD is the LCD driver control voltage input, i.e. contrast regulation. My display shows very good contrast when wired directly to GND. Other display may need a real driver current. You can use a variable resistor (>= 20 kOhm) to do it like this

+5V ---+
       /
       \ <--+
       /    |
       \    |
GND ---+    +--- VL (Pin 3 - driver input)

The PC game port offers several +5V lines that can be used as power supply. You can use

  DB15 pins 1,8,9 or 15 for +5V
            4,5 or 12   for GND

But please try to verify this for your hardware because some soundcards may carry additional signals like a Midi port on those lines. A floppy or harddisk power connector serves also as power supply. Here use the red wire (+5V) and the black wire (GND). CAUTION: The yellow wire carries +12V which would toast your display immediately and may also damage your parallel port!

--------------- snap -----------------
[ top ]