YOn Tue, 21 Oct 2003 16:51:16 GMT, "Gabriel Latrémouille"
tempted fate with:

Has anyone connected several NMEA devices together?
Here is what I am planning.

GPS NMEA output to
1-PC-serial port for navigation software
2-radar to display next waypoint on radar

multiple NMEA capable instruments to
- PC for display within navigation software

Any comments suggestions appreciated

Gaby

Gabriel -

You've lumped several questions together. Rather than try to tell you
what to buy, let me suggest some things to think about first.

1. List all your equipment needs. For instance, you don't mention an
autopilot, which would be a critical consideration.

2. List all your display needs, for instance, do you need instrument
repeaters at the nav station? Is your GPS a chart plotter? How
important is it to have access to charts on the computer? Do you have
a flybridge?

3. If you have an autopilot, will it be driven by a chart program, by
the GPS directly, or do you want to have a choice? For instance,
after having used several PC charting packages, I would never
willingly go back to entering waypoints on the GPS. Nevertheless,
since PCs aren't that reliable compared to a good GPS, I feel it is
critical to be able to fall back to GPS waypoints if the PC fails.
Other people no doubt have other preferences.

4. Would you like to use the PC itself as a repeater display of NMEA
data? Will there be other downstream NMEA data consumers?

5. Be sure you understand the nature of the instrument interfaces you
are using. Are all the devices really using NMEA, or are there some
instruments using SeaTalk in the mix? For instance, my Raymarine
autopilot can run off NMEA or SeaTalk data, but the remote is a
SeaTalk device.

6. Are all the NMEA instruments actually following the specification
exactly? The spec is supposed to be built on RS-422, which has
several benefits. Computer serial ports use RS-232, which is similar
enough to RS-422 for the two to work together, usually. But it is a
bad idea to do this, in my opinion. You really should use a convertor
between the two types of circuits. RS-422 to RS-232 convertors aren't
all that expensive when compared to a fried motherboard on your PC.
The critical feature to look for is isolation, often referred to as
opto-isolation or galvanic isolation. A simple convertor goes from
one NMEEA circuit to one serial port. A multiplexor combines several
NMEA circuits into one serial port. If you select a multiplexor, make
sure it has the isolation feature. I believe that Meindert's have
this. Their specifications generally seem superior to other units on
the market, but I haven't actually used one. I went with a software
solution instead.

To make it more complex, not all NMEA instruments are actually using
RS-422. For instance, my Garmin handheld actually uses RS-232 and has
a typical serial port connector, so no convertor is necessary. My
depth sounder and knotlog seem to be using some sort of hybrid. My
autopilot is an honest to gosh RS-422 interface. When you look at the
wiring instructions, if you see a +, a ground, and a signal wire, you
aren't looking at RS-422. If you see a +, a ground, a signal +, and a
signal -, you have an RS-422. Again, I would never hook an RS-422 and
an RS-232 circuit together directly. Your mileage may vary.

7. To send the GPS signal both to the PC and and the radar, do you
want to split the signal before the PC, or forward the data to the
radar from the PC? Technically, you are supposed to be able to drive
up to 4 NMEA "listeners" from a single NMEA "talker" but I have never
actually done this. You can also buy an NMEA expander which is
designed to drive multiple NMEA circuits, but I think this would be
overkill. Some multiplexors have an NMEA talker port as well as a
serial port, which should work well for you. Don't forget to feed the
autopilot, though.


Just for fun, this is how my NMEA network is rigged.

My GPS (Garmin 48) is plugged directly into a serial port

My DS/KM/Wind is wired to the input side of a B&B NMEA-Serial
convertor.

My autopilot is wired to the output side of the convertor.

The convertor is attached to my laptop USP port via a serial-USB
adapter.

The data from the two serial ports is multiplexed and displayed by my
software. (You could replace this with a hardware multiplexor
attached to one of the ports). Itt displays the data on the PC screen
in nice big numbers that I can see all the way out to the cockpit.
It logs the data to disk.

That's the normal setup. When I want to use the ECS (charting
program) and the autopilot, the wiring stays the same, but the GPS is
attached directly to the ECS. The ECS passes the GPS data and the
autopilot strings it generates through a virtual serial port to my
software, which multiplexes the data with the DS/KM/wind data and
passes the autopilot commands out the USB port to the convertor and
thence to the autopilot.

If the PC was to die, I would unplug the GPS from the PC, and plug it
to the convertor using the gender changer thoughtfully secured to the
convertor.

I tell you all this not as a recommendation for you to follow, but to
illustrate the thought process behind the network configuration. I
hope I haven't confused the situation unnecessarily. It's a beautiful
thing once you get it all working. If you think it through
beforehand, you can save yourself a lot of rewiring, not to mention
you can buy the right equipment the first time.


__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at worldwidewiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/

"Glen Wiley Wilson" wrote in message
news
snip

If you select a multiplexor, make
sure it has the isolation feature. I believe that Meindert's have
this.

That's right. And beware of the new 'improved' model of Noland: this one has
NO galvanic isolation.

To make it more complex, not all NMEA instruments are actually using
RS-422. For instance, my Garmin handheld actually uses RS-232 and has
a typical serial port connector, so no convertor is necessary. My
depth sounder and knotlog seem to be using some sort of hybrid. My
autopilot is an honest to gosh RS-422 interface. When you look at the
wiring instructions, if you see a +, a ground, and a signal wire, you
aren't looking at RS-422. If you see a +, a ground, a signal +, and a
signal -, you have an RS-422. Again, I would never hook an RS-422 and
an RS-232 circuit together directly. Your mileage may vary.

In general: you can connect a RS-232 output to a NMEA RS-422 input by
connecting teh TX or OUT from the RS-232 to the + or 'A' from an NMEA in,
while connecting the - or B from NMEA in to the ground of teh RS-232 output.
The other way around (RS-422 out to RS-232 in) will mosty not work.

Meindert

On Wed, 22 Oct 2003 09:19:20 +0200, "Meindert Sprang"
tempted fate with:

"Glen Wiley Wilson" wrote in message
news
Again, I would never hook an RS-422 and
an RS-232 circuit together directly. Your mileage may vary.

In general: you can connect a RS-232 output to a NMEA RS-422 input by
connecting teh TX or OUT from the RS-232 to the + or 'A' from an NMEA in,
while connecting the - or B from NMEA in to the ground of teh RS-232 output.
The other way around (RS-422 out to RS-232 in) will mosty not work.

Meindert

Yes, I have seen or done both. I even understand why it works that
way. I was merely stating a policy. When I spec something for
navigating a boat it has to be bulletproof, not a marginal "generally
works" type of thing.

Also, I don't like connecting anything to a ground except another
ground. Seems to me to be asking for several different kinds of
trouble. I am not any kind of an engineer, whereas I believe you are,
but that is my policy. As I said, other peoples's mileage may vary,
but I suspect we are more or less in agreement, or your products would
not be what they are.

On a different subject, do you know what's going on with NMEA2000?
Did it wind up being CAN, and is anyone supporting it yet? It looks
like a sweet deal for the instrument makers. RS-232/CAN convertors
are 3 times the price of RS-422/RS-232 and it looks as if they could
potentially lock out anyone who doesn't pony up the fee to get an ID
assigned. But maybe I'm just paranoid...




__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at worldwidewiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/

On Wed, 22 Oct 2003 14:02:52 GMT, "Glen Wiley Wilson"
tempted fate with:

On Wed, 22 Oct 2003 09:19:20 +0200, "Meindert Sprang"
tempted fate with:

"Glen Wiley Wilson" wrote in message
news
Again, I would never hook an RS-422 and
an RS-232 circuit together directly. Your mileage may vary.

In general: you can connect a RS-232 output to a NMEA RS-422 input by
connecting teh TX or OUT from the RS-232 to the + or 'A' from an NMEA in,
while connecting the - or B from NMEA in to the ground of teh RS-232 output.
The other way around (RS-422 out to RS-232 in) will mosty not work.

Meindert

Yes, I have seen or done both. I even understand why it works that
way. I was merely stating a policy. When I spec something for
navigating a boat it has to be bulletproof, not a marginal "generally
works" type of thing.

I forgot to mention that NMEA listeners are supposed to be isolated,
so it should be perfectly fine to attach an RS-232 talker to an NMEA
listener. I'm just not sure everyone implemented that particular
feature, given the workmanship I've seen in the instruments I've
cracked open. So, for the record, when speaking for public
consumption, I prefer to play it safe.

But, as I said before, I'm not an expert and I'm willing to be
educated if I'm wrong.

__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at worldwidewiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/

"Glen Wiley Wilson" wrote in message
...

I forgot to mention that NMEA listeners are supposed to be isolated,
so it should be perfectly fine to attach an RS-232 talker to an NMEA
listener.

That is correct.

I'm just not sure everyone implemented that particular
feature, given the workmanship I've seen in the instruments I've
cracked open. So, for the record, when speaking for public
consumption, I prefer to play it safe.

And that is correct too. Many mfg's have just a single ended input aka 'in'
vs. 'gnd'. Even many with a + and - (differential) you cannot be sure if
they have isolation. Pity that the NMEA organisation does not 'approve'
designs. But rest asu my muxes all have optocouplers inside :-)

Meindert

"Glen Wiley Wilson" wrote in message
...

On a different subject, do you know what's going on with NMEA2000?
Did it wind up being CAN, and is anyone supporting it yet? It looks
like a sweet deal for the instrument makers. RS-232/CAN convertors
are 3 times the price of RS-422/RS-232 and it looks as if they could
potentially lock out anyone who doesn't pony up the fee to get an ID
assigned. But maybe I'm just paranoid...

Well, it's pretty expensive to get NMEA2000 running for the first product.
All standards, testsuites and manufacter- and product ID for the first
product sets you back for $10,500. So I'll stick to NMEA 0183 for a while
:-)

As far as I see it, only the big guys go for NMEA2000.

Meindert

There was a write up in this month's Ocean Navigator. Thus far only 5
products have been fully certified but another 40 are in the process.
Teleflex has a full line of CANbus engine controls. One thing for sure,
it will be more expensive. The prices for just the cable connectors is
outrageous and no doubt we will end up eating our share of the
certification costs. NMEA charges an arm and a leg for almost
everything they do like that.

Meindert Sprang wrote:

"Glen Wiley Wilson" wrote in message
...

On a different subject, do you know what's going on with NMEA2000?
Did it wind up being CAN, and is anyone supporting it yet? It looks
like a sweet deal for the instrument makers. RS-232/CAN convertors
are 3 times the price of RS-422/RS-232 and it looks as if they could
potentially lock out anyone who doesn't pony up the fee to get an ID
assigned. But maybe I'm just paranoid...


Well, it's pretty expensive to get NMEA2000 running for the first product.
All standards, testsuites and manufacter- and product ID for the first
product sets you back for $10,500. So I'll stick to NMEA 0183 for a while
:-)

As far as I see it, only the big guys go for NMEA2000.

Meindert



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Did they change the spec? I got ahold of one of the later prelim specs
and just like 0183, they specified no connectors and were pretty solid
on the fact that the flexability of not specifying them was a good thing.

Doug

"Glenn Ashmore" wrote in message
news:TDylb.86906$sp2.60656@lakeread04...
There was a write up in this month's Ocean Navigator. Thus far only 5
products have been fully certified but another 40 are in the process.
Teleflex has a full line of CANbus engine controls. One thing for sure,
it will be more expensive. The prices for just the cable connectors is
outrageous and no doubt we will end up eating our share of the
certification costs. NMEA charges an arm and a leg for almost
everything they do like that.

Meindert Sprang wrote:

"Glen Wiley Wilson" wrote in
message
...

On a different subject, do you know what's going on with NMEA2000?
Did it wind up being CAN, and is anyone supporting it yet? It looks
like a sweet deal for the instrument makers. RS-232/CAN convertors
are 3 times the price of RS-422/RS-232 and it looks as if they could
potentially lock out anyone who doesn't pony up the fee to get an ID
assigned. But maybe I'm just paranoid...


Well, it's pretty expensive to get NMEA2000 running for the first
product.
All standards, testsuites and manufacter- and product ID for the first
product sets you back for $10,500. So I'll stick to NMEA 0183 for a
while
:-)

As far as I see it, only the big guys go for NMEA2000.

Meindert



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Wed, 22 Oct 2003 00:47:45 GMT, "Glen Wiley Wilson"
wrote:


7. To send the GPS signal both to the PC and and the radar, do you
want to split the signal before the PC, or forward the data to the
radar from the PC? Technically, you are supposed to be able to drive
up to 4 NMEA "listeners" from a single NMEA "talker" but I have never
actually done this. You can also buy an NMEA expander which is
designed to drive multiple NMEA circuits, but I think this would be
overkill. Some multiplexors have an NMEA talker port as well as a
serial port, which should work well for you. Don't forget to feed the
autopilot, though.

In the past, NMEA listeners had quite a relatively low input
resistance that loaded the circuitry, rapidly, to peak current
capacity. But, if you put your ohmmeter to the input of the new
devices, you'll find they act almost like an open circuit.

In our "No Computer" configuration on Lionheart, the RS-232 TX output
from the Noland Multiplexer is applied to the master data output
circuit that feeds all the listeners. Noland warned me it was only
capable of 15ma of current, unlike the TLK NMEA outputs which will
sink a lot more. They told me overloading or shorting wouldn't hurt
the Noland multiplexer, it would simply not have sufficient output
levels to key the listeners.

The listeners connected to the master data output a
Icom M602 VHF xcvr
Icom M802 HF-SSB xcvr
Raymarine RL70CRC radar/chartplotter
Garmin 185 GPS/Sonar
B&G Network Pilot autopilot
B&G Yeoman paper chart drafting table
and, at times, a Dell Latitude P4 notebook computer's serial port when
someone forgets to flip the switch to COMPUTER ON.

With all these loads, the 15ma output limit of the Noland multiplexer
runs them all just fine with valid data. Nothing seems unstable.....



Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?

On Wed, 22 Oct 2003 13:22:48 GMT, (Larry W4CSC)
tempted fate with:



In the past, NMEA listeners had quite a relatively low input
resistance that loaded the circuitry, rapidly, to peak current
capacity. But, if you put your ohmmeter to the input of the new
devices, you'll find they act almost like an open circuit.

In our "No Computer" configuration on Lionheart, the RS-232 TX output
from the Noland Multiplexer is applied to the master data output
circuit that feeds all the listeners. Noland warned me it was only
capable of 15ma of current, unlike the TLK NMEA outputs which will
sink a lot more. They told me overloading or shorting wouldn't hurt
the Noland multiplexer, it would simply not have sufficient output
levels to key the listeners.

The listeners connected to the master data output a
Icom M602 VHF xcvr
Icom M802 HF-SSB xcvr
Raymarine RL70CRC radar/chartplotter
Garmin 185 GPS/Sonar
B&G Network Pilot autopilot
B&G Yeoman paper chart drafting table
and, at times, a Dell Latitude P4 notebook computer's serial port when
someone forgets to flip the switch to COMPUTER ON.

With all these loads, the 15ma output limit of the Noland multiplexer
runs them all just fine with valid data. Nothing seems unstable.....


Interesting. I'd have bet money that would be a flakey setup. You
learn something every day (well you do if you're paying attention.)
If I felt sure that my customers had someone of your expertise aboard,
I might even be comfortable recommending something like that. :-)


__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at worldwidewiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/