Modern Blinkenlights

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Jun 18 14:13:01 2004

> 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.

Are you serious? If so, I have to wonder if anyone can actually _design_
any more, or if they just throw standard modules together and hope it works.

Let me see if I understand this. You have a digital value (system usage),
on a digitial machine (the linux box). You convert it to analogue. You
then re-convert it to digital with a very low-res ADC (the LM3914 (I
guess) bargraph chip. Why not just output a suitable value on the
parallel port (which has 12 output lines IIRC) to directly drive the LEDs
(the 3914 drives 10 LEDs at most).

-tony
Received on Fri Jun 18 2004 - 14:13:01 BST