"Bill Kearney" wrote in
:

So I'll go back to my guess that the application layer is the same
but the underlying layers (transport to physical) have been altered
to NMEA 2000.

Incorrect. The bridge cable is passive. The NG cabling, it appears,
just has extra wiring to accomodate the older SeaTalk network. I'm
guessing they did this to allow bringing older SeaTalk gear into the
network without having to run a lot of additional cabling. That is,
bring a line off an older SeaTalk-based transducer and tee it into a
new NG network. Leaves them an opening to attaching existing gear
(sensors, gauges and the like) to the new network. So if you pulled a
new NG 'backbone' network you would be able to connect any older gear
onto the cable without keeping the old network.

It would not have made much economic sense to go with the NMEA2k
protocol stack and not take advantage of the economies of scale
offered by standards-based chipsets.

-Bill Kearney

I'm lost. You say "incorrect" and then state that the cable is passive.
If it's passive, then the my statement is correct. Also, here's the link
to the document describing the SeaTalk protocol:

http://www.thomas-knauf.de/rap/seatalk2.htm

If you look at the datagram definitions, you'll see lots of parameters
which are highly specific to RayMarine equipment and have no mapping to any
NMEA sentances. I've never seen a document describing NMEA 2000, so I
can't comment on that. However, I can't imagine mapping the all of the
SeaTalk datagrams to NMEA 2000 and back. With tons of existing equipment
out there, you need to provide a method of backwards compatibility.

I just looked at the RayMarine ST70 documentation and you can bridge a
SeaTalk network onto a SeaTalkNG network through an ST70 instrument. There
is no way to directly connect a SeaTalk network to a SeaTalkNG network.

Also, you are NOT supposed to bridge a SeaTalk network to a SeaTalkNG
network with NMEA 2000 devices on it. I'm not sure what this implies.

-- Geoff
www.GeoffSchultz.org

Followup to msg on Wed, 5 Mar 2008 09:26:30 -0500, "Bill Kearney"
:
(Original msg on bottom)

I see ... that's why I have see some drawing where the net is tapped (
I mean terminated) like the ethernet PC net.

For NMEA 2000 I found as a good doc:

http://www.jackrabbitmarine.com/file..._Design_v2.pdf

Thanks
Manlio




"Manlio" wrote in message
.. .
Presented by Raymarine in 2007, I am unable to find around a white
paper or some clear and complete presentation of this protocol.
Someone may give me an hint ?

Isn't it just NMEA 2000 with different connectors?

To that end there aren't any free docs for NMEA 2000 online anywhere either.
Cough up a couple grand, that's the only way to get it.

(Original msg on bottom)

I agree that Jack Rabbit's NMEA doc is valuable. So are Maretron's
design guide and the Simnet, LowranceNet, and SeaTalkng manuals.

I've been testing SeaTalkng, along with an ST70, an E Series MFD, and
a Garmin 5212, along with a standard N2K network of Maretron
sensors,.
Bottom line: STng is just another way to do NMEA 2000 cabling, with
some pros and some cons, and patch cables are available if you don't
want to use it. But it's all NMEA 2000 and the messages move around
pretty darn well, even across brands. For more, see www.panbo.com.


On Mar 9, 5:46*am, Manlio wrote:
Followup *to *msg on Wed, 5 Mar 2008 09:26:30 -0500, "Bill Kearney"
:

I see ... that's why I have see some drawing where the net is tapped (
I mean terminated) like the ethernet PC net.

For NMEA 2000 I found as a good doc:

http://www.jackrabbitmarine.com/file..._Design_v2.pdf

*Thanks
Manlio



"Manlio" wrote in message
.. .
Presented by Raymarine in 2007, I am unable to find around a white
paper or some clear and complete presentation of this protocol.
Someone may give me an hint ?

Isn't it just NMEA 2000 with different connectors?

To that end there aren't any free docs for NMEA 2000 online anywhere either.
Cough up a couple grand, that's the only way to get it.