Date: Wed, 30 Jul 2003 20:50:02 +0200
From: Marc Giger <gigerstyle@gmx.ch>
To: Pavel Machek <pavel@suse.cz>
Cc: John Bradford <john@grabjohn.com>, linux-kernel@vger.kernel.org,
       pgw99@doc.ic.ac.uk
Subject: Re: PATCH : LEDs - possibly the most pointless kernel subsystem
 ever
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In-Reply-To: <20030730174457.GI10276@atrey.karlin.mff.cuni.cz>
References: <200307301608.h6UG8YQJ000339@81-2-122-30.bradfords.org.uk>
	<20030730174457.GI10276@atrey.karlin.mff.cuni.cz>
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Hi All,

On Wed, 30 Jul 2003 19:44:57 +0200
Pavel Machek <pavel@suse.cz> wrote:

> Hi!
> 
> > > But this kind of blinkenlights needed pretty fast LEDs. (At 486
> > > time I decided that parport on ISA is fast enough..)
> > 
> > I'll buy some LEDs and build a parallel port connected LED panel
> > tomorrow...  Do you think the overhead of driving the LEDs would
> > have too much of a negative effect on system performance?  If so, or
> > if we

Yesterday I connected 8 LED's to the parallelport datalines. Today I
read this thread. What for a coincidence...
The goal of this "project" was to show the current cpu load. It works
great now! I can see randomly the LED's lightening up while I am writing
this mail:-))

> 
> I'm not sure. At 486 days I was pretty sure it did not matter. These
> days you might get 10% slowdown on some microbenchmark, or something
> like that. I do not think it can slow down common tasks.
> 
> My construction of LED lights is extremely flaky, and I'm afraid of
> burning printer port. At 486 days ports were expected to survive such
> abuse. Not sure if todays EPP/wtf ports can handle that.
> 								Pavel

At beginning I had some fear to connect LEDS directly to the parport,
because its an onboard controller (like the most mainboards have).
I don't notice system performance slowdowns. (CPU Load code was borrowed
from xosview:-))

My personal goal would be to controll a Dot-Matrix Display. The
Display should show something like the actual CPU temperature,
CPU-load, processes, s.m.a.r.t state, etc etc etc etc..........But my
problem is how to beginn with that. I would prefer to controll it with a
PCI card. Also I looked today at 68HC11 microcontrollers, which I can
connect to the serial port and transmit the needed infos.

Are there suggestions / comments / questions?

If somebody is interested to develop such a card / controller with me, I
will be pleased to hear from you!

Thank you

Marc
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