Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 30 Jul 2003 21:06:18 +0200 | From | Marc Giger <> | Subject | Re: PATCH : LEDs - possibly the most pointless kernel subsystem ever |
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On Wed, 30 Jul 2003 20:56:59 +0200 Herbert Pötzl <herbert@13thfloor.at> wrote:
> 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)
5mA per LED on the same line. 40mA if you connect all to the same dataline or GND-line.
> > 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 ;) ...
Are you sure?? I thought this is true for serial-port...
> > HTH, > Herbert > > PS: I usually use 220Ohm and no external power ...
The same here...
greets
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