[Soekris] net4521 GPIO for serial data

[Joseph Barstow]

Hi all,
     Quick question which may not have a very quick answer, but here
goes anyway:  How easy would it be to connect a GPS unit directly to
the GPIO pins of a net4521 and get useful data out of it?  The model
I'm using is the Garmin 15-H.  Although I know it's been batted around
here more than once before, I was unable to find conclusive evidence
one way or another.
     I should mention I don't have a background in low-level serial
programming, so I'm not even sure if it's possible to take a 4800bps
stream directly from the GPIO pins without a hardware intermediary.
Can it be done completely in software, and if so, could anyone give
some pointers or perhaps links to further my knowledge? Ideally I'd
like to do this using the GPIO as some sort of "virtual serial port",
which could then be accessed by GPSd.  I've looked through the User's
Manual for the SC520, but after 30+ pages, I still have no clue what
I'm actually dealing with.  I'm pursuing this because I need to add a
GPS data stream while maintaining use of both cardbus slots and the
serial console.

Thanks in advance,
Joe