[mythtv-users] Laptop - front end question...

Craig Huff huffcslists at gmail.com
Sat Sep 15 00:44:30 UTC 2007

On 9/14/07, David Brodbeck <gull at gull.us> wrote:
> Just brainstorming here -- If your laptop has a "wake on ring" feature in
> its BIOS, you might be able to interface that device to the serial port and
> avoid opening up the machine.  I think you'd just have to pull the RI (ring
> indicator) pin high.  This is pin 9 on a DB-9 serial port.  Note that RS-232
> uses negative voltages to indicate a logic 1, so that means applying -3 to
> -12 volts.  You could probably test it with a 9-volt battery before spending
> any money on hardware.

I have been working on a solution for my desktop that doesn't seem to wake
on USB events, even though it is supposed to, so I was testing the wake on
ring feature myself.  I was able to trigger a wakeup by applying +5v from
one of the 5vsb pins on the motherboard, so it might not be necessary to
come up with a negative voltage.  Considering I was testing with a voltmeter
probe as a jumper, it might just as easily have been the "disconnecting" of
the +5v that did it as opposed to the "connecting", but does it matter which
edge of a pulse?  Not in my book ;-)

I'd give that a whirl before I tried to come up with a negative voltage
solution.  It can be done, but why complicate things if you can get a
voltage source from the laptop's ports (like a USB port with standby power?)
ready-made for use to trigger the WOR.

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