Some demos, back when the Demo Scene was more lively, used the keyboard leds as an added visual fascination device of some sort.

Music on your adlib card, moving shapes on your 320x200 256 color display, and some 80s Knight Rider style moving light effect on your 3x1, 2 color keyboard led display.

Humanity was once hopeless.

I don't think that's useful. Some people apparently did.

On the hardware side of this idea: With a little soldering, you can turn any LED on your PC into a much more fun accessory.

For example, Instead of a single, tiny light blinking when your HD is accessed, you can wire the light to a whole rack of LEDs, so that your computer's thought processes are much more visual.

I took the front of an old modem (extra credit if you rememer what TR HR HS OH CD SD RD stand for) and soldered all the LEDs together. With some speaker wire, I spliced that to the light on the front of my PC. Now when I tell it to do my bidding, it tells me with big red lights "YES MASTER!!!"

Or you could use them for Winamp Visualization!
Stefan Slonevskiy has created a visualization plugin for everyone's favorite corporate sellout
It makes your keyboard lights act like an analyzer, adjustable sensitivity and everything!
Granted, it's a ridiculously random trinket, but I like trinkets
He has also created a C++ lib for those who want to include keyboard light tomfoolery in their apps
all this and more can be acquired at his website: http://www.slonsl.nyczone.net/index.php
I use my keyboard leds for three things: num lock flashes when someone sends me an aim message, caps lock flashes when someone says something on irc with my name in it, and scroll lock lights up when I have new mail.

It's quite easy changing the state of your leds if you're using linux. here is a perl example that works both in console and X:

#!/usr/bin/perl
open(FH, "/dev/tty1") or die "open";
ioctl(FH, 0x4b32, 1); # scroll lock on
ioctl(FH, 0x4b32, 2); # num lock on
ioctl(FH, 0x4b32, 4); # caps lock on
ioctl(FH, 0x4b32, 0); # all off
close(FH);

Remember to put some kind of sleep statement there if you want to see anything. Because this script calls ioctl(), it does have to be run as root.

This is a blinking script I use when my attention is needed:

#!/usr/bin/perl
use Time::HiRes qw( usleep );
open(FH, "/dev/tty1") or die "open";
ioctl(FH, 0x4b32, 0); # all off
while (1) {
ioctl(FH, 0x4b32, 2); usleep (50000);
ioctl(FH, 0x4b32, 0); usleep (50000);
$counter++; if ($counter == "10") { close(FH); exit; };
}

Other examples:

ioctl(FH, 0x4b32, 3); # scroll lock and numlock
ioctl(FH, 0x4b32, 6); # caps lock and numlock
ioctl(FH, 0x4b32, 5); # scroll lock and caps lock
ioctl(FH, 0x4b32, 7); # everything

Have fun!
While the above are all very interesting uses of keyboard lights, they still don't seem to qualify as "something useful". From my point of view, they're right up there with case mods in terms of usefullness.

But fear no more!

Your LEDs can be put to something that actually is useful in certain circumstances.

Which ones, you ask? Let's take the hypothetical situation in which you are stuck in a prison in the Phillipines, with massive amounts of free time, a laptop, and some important information to decrypt. Furthermore, you are quite certain that you're the victim of a massive conspiracy spanning some 50 years, and this conspiracy has the power to find out what's displayed on your monitor using Van Eck Phreaking.

So, pipe the output of your decrypted text to the keyboard lights. Make the lights blink in Morse Code to figure out what the text is. This will take you massive amounts of time, of course, but, after all, you're in prison. Also, you have the kind of ruthless discipline required to sit through the blinking of the LED and figure out what it's saying because of your sudden aversion to masturbation.

 

OK, I'll be honest. I didn't come up with this. Neal Stephenson did in his Cryptonomicon. But it's the one use of keyboard lights that's not utterly useless.

So, rejoice, conspiracy buffs, and take off that aluminum foil hat! You can now re-read your important JFK assasination theories using your keyboard! Hurrah!

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