Hi,

PROBLEM:

There is a bug in the serial port code of garble such
that it does not set the serial port it uses for the GPS
to raw mode.  Some ports, notably the /dev/ttyS0 etc. recommended by the README for connecting with the GPS do
some processing by default on the input so that the Garmin GPS data gets corrupted.

FIX:

Use /dev/cua0 or /dev/cua1 -- these ports do not do any processing by default.  Also, I think that running

stty -f /dev/gps raw

will also turn off all the  unwanted processing.  Replace
/dev/gps with the suitable device name.

There will be patch posted for this within the next few days.