"Meindert Sprang" wrote in message
...
"Pascal Goncalves" wrote in message
om...
Anibody can tell me the diferences betwen V3.1 and V2.0? Or better,
who have the NMEA 183 specs can send me a copy?

The NMEA specs are copyrighted material and can only be obtained, at a
cost,
from www.nmea.org.

I read somewhere that
the V 3.1 alows for more than one talker: this is true?

No. Data from more than one talker can only be combined using an NMEA
multiplexer.

Meindert



Hi,
Meindert is right, a multiplexer is necessary to combine talkers.
However, with the various versions of NMEA sentences and the resulting
compatibility problems, it is advantageous to purchase an "intelligent"
multiplexer, one that allows you to do NMEA conversions, insert extra fields
in a sentence, etc.
There is one such multiplexer on the market that allows you to convert
entire sentences "on the fly", e.g. to convert a GGA to a RMC sentence, or
to insert extra fields, to make your older equipment compatible with NMEA
3.01. It also allows you to suppress sentences that your software doesn't
need (filtering), change NMEA ID's and many more other functions. Of
course, the checksum is re-calculated and replaced after changes have been
made to the original sentence. All these functions are controlled by
user-definable directives in a script file and can be uploaded to the
multiplexer in a simple way.
The same multiplexer has a "data pacing" feature to slow down fast talkers,
such as some electronic compasses. It will also add extra safety to the
integrated system by switching automatically to a backup GPS when the
primary GPS stops outputting NMEA data. This happens more often than one
would think and usually at a time it is most inconvenient. So, this is
actually a multiplexer taken a few steps further.
All to good to be true? A Google search for "NMEA mux" will get you there.

Wout