Modern Blinkenlights

>> -----Original Message----- >> From: cctalk-bounces(a)classiccmp.org >> [mailto:cctalk-bounces@classiccmp.org] On Behalf Of Tony Duell >> Sent: Friday, June 18, 2004 3:13 PM >> To: cctalk(a)classiccmp.org >> Subject: Re: Modern Blinkenlights >> >> > 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 >>