Modern Blinkenlights

From: JP Hindin <jplist_at_kiwigeek.com>
Date: Fri Jun 18 17:41:17 2004

On Fri, 18 Jun 2004, Ethan Dicks wrote:
> On Thu, Jun 17, 2004 at 11:41:09PM -0500, Doc Shipley wrote:
> > Bah! I'll take the CPU-monitor LEDs on my BeBox any day!

> I've seen a pretty easy-to-build circuit to put one of those on a
> Linux box. I remember something about a simple resistor ladder
> network D-A and an LED bargraph chip from Radio Shack. The software
> just puts the load on a spare parallel port, so it's pretty low-impact.
> -ethan

I decided that if I could have a BeBox with LED meters, then I'd better
make myself my own.
I have eight LEDs (four green, two yellow, one orange, one red - fluke in
colour arrangement as I was ripping them off from old AT cases), each of
which has a 220 ohm resistor in series to a DB25 header. I used a spare
straight-through serial ribbon cable to hook it to the parallel port.

I use Linux's /proc/stat to read CPU load, and then a extremely simple C
library ("parapin") in XS coupled to a perl script (I do better with perl
than C) to turn the lines on and off.

Works a lot better than I would have imagined, considering how much of a
bodge job it is. I'm too embaressed to take pictures of the solder work,
lest I croak of shame.

JP
Received on Fri Jun 18 2004 - 17:41:17 BST