From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S273272AbTG3S4x (ORCPT ); Wed, 30 Jul 2003 14:56:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S273273AbTG3S4x (ORCPT ); Wed, 30 Jul 2003 14:56:53 -0400 Received: from www.13thfloor.at ([212.16.59.250]:32682 "EHLO www.13thfloor.at") by vger.kernel.org with ESMTP id S273272AbTG3S4v (ORCPT ); Wed, 30 Jul 2003 14:56:51 -0400 Date: Wed, 30 Jul 2003 20:56:59 +0200 From: Herbert =?iso-8859-1?Q?P=F6tzl?= To: Pavel Machek Cc: John Bradford , linux-kernel@vger.kernel.org, pgw99@doc.ic.ac.uk Subject: Re: PATCH : LEDs - possibly the most pointless kernel subsystem ever Message-ID: <20030730185659.GA7260@www.13thfloor.at> Reply-To: herbert@13thfloor.at Mail-Followup-To: Pavel Machek , John Bradford , linux-kernel@vger.kernel.org, pgw99@doc.ic.ac.uk References: <200307301608.h6UG8YQJ000339@81-2-122-30.bradfords.org.uk> <20030730174457.GI10276@atrey.karlin.mff.cuni.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20030730174457.GI10276@atrey.karlin.mff.cuni.cz> User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 30, 2003 at 07:44:57PM +0200, Pavel Machek 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 > > 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. parport uses 5V (actually a little less) so if you use normal (not extra super duper bright) leds and put a 1kOhm resistor in front of each led, then it will drain 5mA per led, which gives a total of 40mA for eight leds (for example) now for the parport: depending on the technology and the age of the circuit, it provides between 2 and 14mA output at >2.4V (the led usually requires less than 1.5V to operate) so this would be within the range ... but, if you want either extra brightness or extra security, you could provide +5V and use the outputlines as sink, which then is between 15 and 25mA ... anyway, parport should be short circuit safe, so the worst what could happen is, that the leds are not working ;) ... HTH, Herbert PS: I usually use 220Ohm and no external power ... > -- > Horseback riding is like software... > ...vgf orggre jura vgf serr. > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/