[mythtv-users] LED recording indicator

[Brad Templeton]

On Tue, Jan 25, 2005 at 01:24:28AM -0600, Robert Denier wrote:
> Well the two most obvious ways are using a spare serial port or a 
> parallel port.  The most obvious that comes to mind is to take your 
> average IR blaster and duplicate it with a visible led rather than an 
> ir  one. 
> 

Seems to me that since he probably doesn't want the HDD LED to do the
job, it would make sense to just use that LED.  Remove it from the 
HDD jumper and connect it to your new source.

Many motherboards have an IRDA header on them that is not used, it
is meant to drive an IRDA LED.   I have not done this but I would take
a wild guess (test with voltmeter first) that you could probably just
put the HDD LED or some other front panel LED, and wire it to the right
two wires in the IRDA header, since that is set to run your LED.

Then you probably could turn it on in software.   The IRDA header
is sometimes just another COM port, sometimes it does high speed 
IRDA, multi-megabit.   Either way, if you send it data that keeps it
mostly on, it will light up.  The user won't see the flicker.

Or modify the driver to allow you to just turn it on and off.

This seems a lot easier.  If you don't use your IRDA header, and
few people do.

Other headers you could possibly use would be an extra com port
header (which will be at 12v though, so you need an additional resistor)
or possiby you even have a spare parallel port header, I have seen
them.   You will have USB headers which have +5v but that's on all the
time, I don't know if you can switch it off.   Their data ports will be
under the control of your USB drivers.

You also may have extra fan headers.  These tend to be 12v but use
a voltmeter.  More to the point, they often can have the voltage tuned
for variable speed fan.   You can probably turn them on and off in
software too.   Check voltage and add an appropriate resistor to get
the right voltage drop over your HDD LED.