if its an older nmea standard others have used different serial adapters to receive results.
http://forum.openmarine.net/showthread.php?tid=1003
Didier B did a good write-up pdf.
http://forum.openmarine.net/attachment.php?aid=253
http://forum.openmarine.net/showthread.php?tid=1003
Didier B did a good write-up pdf.
http://forum.openmarine.net/attachment.php?aid=253