18 Jun
2004
18 Jun
'04
8:41 a.m.
On Friday 18 June 2004 20:13, Tony Duell wrote:
I don't know the one he's talking about but the most popular one all over
the web (and the one that i've got lying around from my old mail server)
just has 10 LEDs driven directly from the port with a common resistor.
alex/melt
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