Add Buttons Support via LPT port

[secadmin]

Hello,
***INTRODUCTION***
I looked through various LCD options including
beautiful but rather expensive 'brand name' LCD's being
connected via serial port/USB. As you see, I prefer
parallel port (later - LPT port) connected 'cheapie'
display (BTW, 40x4 isn't that cheap!). One thing I'm
constantly missing is buttons for my LCD. Yes, you'd
like to say about building a microprocessor-based board
for LCD with serial connection, and the buttons are a
pleasant add-on here. But I'm not about to go that hard
way. I'm a bit lazy.
***BODY***
While connecting former Centronics cable to the LCD, I
noticed a lot of signal wires being unused. While
investigating the LPT port specs I found that only
upstream signal is used (upstream = directed from host
to the peripherial device). I don't thing you're
amazed, as we don't read anything from an LCD (even R/W
pin is constantly grounded).
***IDEA***
There are several downstream wires on LPT port. They
aren't used. But they can be easily connected to
buttons (as we already got external +5V voltage).
***TECHNICAL DETAILS***
Here's the pinout of LPT port:
http://pinouts.ru/ParallelPorts/ParallelECP.shtml
And here are the circuts for interfacing LPT to LCD:
http://lcdsmartie.sourceforge.net/circuits.htm
As we see, pins 10-13,15 aren't used.
Upon cursory reading of port's specs pins 10-13 can be
used to transfer info to the host = the buttons can be
connected to them.
***QUESTIONS***
1)I'm not sure yet if our port driver 'port95NT' is
able to read the states of downstream pins. I'd be glad
if someone with this software knowledge could provide
me the details.
2)I'd like to know if such button support can be added
to the program.
3)The way of physical connection of buttons to the port
requires further investigation. I got electronics
experience so I'm able to do that.
***P.S.***
1)TIP: I made an external LCD (try putting 40x4 LCD to
the tower case!). The question was how to power the LCD
with no more wires. I used disconnected, unneeded wires
from the Centronics cable to power LCD. There are lots
of them to provide good current with little loss, but
they are to be connected in parallel. While looking
into opened 25pin parallel port plug, you may notice
there are plenty of room. I bought a 3mm power supply
connector and mounted inside the 25pin plug. 5V from
the PC is connected via 3mm coaxial connector. You can
also use external power supply to reduce risks of
short-circuit'ing the 5V line of main PSU on your
expensive PC system. I used iPAQ's power supply for
testing.
2) I have an amateur experience in Delphi programming
(like TCP/IP LAN chat). I can try to help in developing
LCD Smartie as I really like the program. I'm a
windoze system administrator and i'm interested in
writing some plugins to put on an LCD a server
statistics like the number of active users on shared
disks.

P.S. I also created the same topic in SourceForge's Feature Request Page

[Dirkus]

Seeing as my LCD is already endowed with terminal feeping creaturism, I'd like to see this as well. This was the one thing I had found myself wishing I could do. Ideas anyone?

[EvylRat]

I too would be interested in this for my headless server box. Have a push button or two on a PCI card (case cutting case) to cycle across screens quickly

[mattcro]

In case you missed it...

Buttons on LPT has been implemented as a Smartie plugin. You can have 4 buttons (up to 16 with some tricky wiring) on the same parallel port as your LCD.

See: http://forums.lcdsmartie.org/viewtopic.php?t=876

[EvylRat]

Thanks