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Old 15-04-2013, 11:41   #1
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NMEA into Router

Hi everyone,

I have a Apple AirPort Extreme router and want to feed my NMEA 0183 data into one of the routers LAN (RJ45) ports to transmit the NMEA along with other data to my iDevices.

I have a Shipsmodul multiplexer with RS323 output as well as USB output. Regarding NMEA, I am only wanting to transmit GPS and my raymarine data via wi-if.

Can I do away with my multiplexer and input the GPS and raymarine NMEA 0183 in there "raw" RS232 form directly into two separate RJ45 ports? If so how will I wire my NMEA rx and tx to the RJ45 plug?

The reason why I don't just buy a nmea to wifi transmitter is because I want 3G internet as well as connection to my Apple TV on the network.

Any advice/help will be appreciated.

Thanks,
Robert
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Old 15-04-2013, 12:06   #2
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Re: NMEA into router

No, you can't wire RS-232 directly to the router's RJ-45. You need a Serial-to-Ethernet converter. I use a Lantronix UDS2100. The UDS can handle two ports, but I don't know why you'd want to remove the multiplexer. Better to keep the GPS and Raymarine NMEA together, I think.
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Old 15-04-2013, 13:16   #3
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Re: NMEA into router

its actually more complicated then that , just converting the 0183 data into a ethernet convertor will not solve the issue. You need to encapsulate the data into tcp/ip formatted packets, You need a nmea to wifi bridge, Chetco, Digital yacht.

Its a techie orientated solution at the moment.

dave
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Old 15-04-2013, 13:25   #4
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Re: NMEA into router

I second JayH's thoughts.

If you don't want to buy a dedicated NMEA-0183 to ethernet box, if you run a nav computer connected to the airport, feed the usb from your multiplexer into that and run a program that will take the data from the serial line and put it out over the network. OpenCPN will do this for you. If you don't want a full featured chartplotter, Look at NavMonPC if your nav computer runs Windows or kplex if Linux. If OSX, kplex will run happily on it, but there's no OSX .dmg or GUI, so you'd need xcode and not be afraid of the command line or compiling from source to get it running.

An alternative would be something like a raspberry pi model B powered from a 12v to 5v converter (e.g. micro usb phone charger) usb from multiplexer in, run kplex, ethernet out connected to the airport. Sorted for ~$50.

Not industrially robust, but then neither is an airport or an i-thing.
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Old 15-04-2013, 13:41   #5
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Re: NMEA into router

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Originally Posted by goboatingnow View Post
its actually more complicated then that , just converting the 0183 data into a ethernet convertor will not solve the issue. You need to encapsulate the data into tcp/ip formatted packets, You need a nmea to wifi bridge, Chetco, Digital yacht.
Whilst you're absolutely correct that throwing out raw ethernet frames is no use to the OP's i-apps and the data needs to be encapsulated in either tcp or udp over IP, these electronic engineers and marketing people aren't very good at distinguishing their protocols in the stack, so I believe "NMEA to ethernet" converters like JayH pointed to actually do the higher layer encapsulation as well, in the same way that "NMEA to Wifi" (ie 802.11) converters do. In the context of the Yacht AL's requirements, an "NMEA-0183 to ethernet" converter is probably a better plan than the NMEA to Wifi converters as, plugged into the airport, it keeps everything on the same wireless network rather than creating a new one
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Old 15-04-2013, 13:52   #6
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Re: NMEA into router

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Originally Posted by muttnik View Post
Whilst you're absolutely correct that throwing out raw ethernet frames is no use to the OP's i-apps and the data needs to be encapsulated in either tcp or udp over IP, these electronic engineers and marketing people aren't very good at distinguishing their protocols in the stack, so I believe "NMEA to ethernet" converters like JayH pointed to actually do the higher layer encapsulation as well, in the same way that "NMEA to Wifi" (ie 802.11) converters do. In the context of the Yacht AL's requirements, an "NMEA-0183 to ethernet" converter is probably a better plan than the NMEA to Wifi converters as, plugged into the airport, it keeps everything on the same wireless network rather than creating a new one
Correct, these terminal servers (called "device servers" nowadays) do full encapsulation and work exactly like the "marine" products.
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Old 15-04-2013, 13:55   #7
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Re: NMEA into router

yes, ones that are designed for nmea to ethernet or nmea to wifi will do encapsulation ( even if there is no standard) , I was referring to the comment about using a simple serial to ethernet covertor

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Old 15-04-2013, 14:04   #8
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Re: NMEA into router

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Originally Posted by goboatingnow View Post
yes, ones that are designed for nmea to ethernet or nmea to wifi will do encapsulation ( even if there is no standard) , I was referring to the comment about using a simple serial to ethernet covertor

dave
You are a little lost Dave, the device mentioned works like you think only NMEA to Ethernet converters work. NMEA 0183 is just serial data strings like from any old computer terminal. Terminal servers encapsulated that into TCP so that only a network cable was needed to wire a whole cluster of serial terminals. That is the history of these nifty little boxes.

You just config them like "this serial port needs to be encapsulated in TCP with that port number to this network address etc.
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Old 15-04-2013, 14:30   #9
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Re: NMEA into router

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You are a little lost Dave
No I was the one who was lost and misunderstood his post, thinking he was replying to post 2 but actually he was replying to post 1.

On a different note...

A general purpose "device server" is not going to be as functional as software which is dedicated to the purpose of shifting NMEA-0183 around. It won't know about NMEA-0183 checksumming. It probably won't be able to distribute its input via a tcp server to multiple clients and via udp broadcast (let alone multicast). It won't be able to offer 2-way connections multiplexing data from multiple network connections as well as the serial input and it won't be able to do sentence filtering or prioritisation of data sources. You can tell I'm biased :-)
Edit: Err...not of course that you necessarily need that functionality...
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Old 15-04-2013, 15:00   #10
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Re: NMEA into router

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Originally Posted by s/v Jedi View Post
You are a little lost Dave, the device mentioned works like you think only NMEA to Ethernet converters work. NMEA 0183 is just serial data strings like from any old computer terminal. Terminal servers encapsulated that into TCP so that only a network cable was needed to wire a whole cluster of serial terminals. That is the history of these nifty little boxes.

You just config them like "this serial port needs to be encapsulated in TCP with that port number to this network address etc.
I know how they work Nick, Ive been around them for years.

But the fact is you cannot reliably carry 0183 simply parcelled up into a ethernet stream, The software at the other end must be written specifically to handle the vagaries of the data stream , try encapsulating AIS feeds this way.

Then you have the issue of rebroadcasting the 0183 onto a wifi or ethernet , again theres no standard ( for example no way to identify sources , other then by assumption )

At least the dedicated nmea to ethernet/wifi usually encapsulate into a documented format ( ie their format).

i not saying it cant be done, im saying its not that simple thats all. I can do , you can do , can the OP , no I dont beleive so.

dave
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Old 15-04-2013, 15:56   #11
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Re: NMEA into router

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Originally Posted by goboatingnow View Post
I know how they work Nick, Ive been around them for years.

But the fact is you cannot reliably carry 0183 simply parcelled up into a ethernet stream, The software at the other end must be written specifically to handle the vagaries of the data stream , try encapsulating AIS feeds this way.

Then you have the issue of rebroadcasting the 0183 onto a wifi or ethernet , again theres no standard ( for example no way to identify sources , other then by assumption )

At least the dedicated nmea to ethernet/wifi usually encapsulate into a documented format ( ie their format).

i not saying it cant be done, im saying its not that simple thats all. I can do , you can do , can the OP , no I dont beleive so.

dave
No, all they do is encapsulate NMEA0183 into TCP frames. What they change is the port number, for example Furuno uses a different one than the rest. It is pretty primitive but that is also the reason that it easily works to an iPad etc. There is no question about it, this just works. You only need to know which TCP port. In case of broadcasting, this is UDP, not TCP

See here for Panbo using the "same" device just with another name label on it: Panbo: The Marine Electronics Hub: NMEA 0183 over Ethernet, on Mar Azul
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Old 15-04-2013, 16:06   #12
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No, all they do is encapsulate NMEA0183 into TCP frames. What they change is the port number, for example Furuno uses a different one than the rest. It is pretty primitive but that is also the reason that it easily works to an iPad etc. There is no question about it, this just works. You only need to know which TCP port. In case of broadcasting, this is UDP, not TCP

See here for Panbo using the "same" device just with another name label on it: Panbo: The Marine Electronics Hub: NMEA 0183 over Ethernet, on Mar Azul
Using a moxa , or any of the others , you can generate the equivalent of a Ethernet serial cable. In the case you mentioned they used the serial driver that moxa uses to implement a effective serial VPN.

What I was saying that the client of the serial bridge must understand the encapsulation to handle the stream if it does great , if it doesn't ......

Dave
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Old 15-04-2013, 16:13   #13
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Re: NMEA into router

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Using a moxa , or any of the others , you can generate the equivalent of a Ethernet serial cable. In the case you mentioned they used the serial driver that moxa uses to implement a effective serial VPN.

What I was saying that the client of the serial bridge must understand the encapsulation to handle the stream if it does great , if it doesn't ......

Dave
Indeed, the client must understand it. As it is plain NMEA0183 that is in there, they all understand it

Everybody thinks that this is all complicated but it isn't; even Furuno NavNet is just NMEA0183 encapsulated into TCP frames. Simple virtual serial port drivers can pick it up. Software like MaxSea (since version 11 IIRC) can even output those streams; I think everybody copied that.

These device server have evolved though; I now see that they have an internal webserver to configure them so much more modern than what we used to have in the old days (hitting key-combinations on the terminals LOL).
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Old 15-04-2013, 16:24   #14
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Indeed, the client must understand it. As it is plain NMEA0183 that is in there, they all understand it

Everybody thinks that this is all complicated but it isn't; even Furuno NavNet is just NMEA0183 encapsulated into TCP frames. Simple virtual serial port drivers can pick it up. Software like MaxSea (since version 11 IIRC) can even output those streams; I think everybody copied that.

These device server have evolved though; I now see that they have an internal webserver to configure them so much more modern than what we used to have in the old days (hitting key-combinations on the terminals LOL).
No nick its not that simple , of you examine the encapsulated frames of many serial port severs , you will see subtle differences, some add prefixs or suffixes to identify sources ,etc. yes you can strip this away and you get a 0183 stream, but its either a virtual serial port software , back to back serial bridge or a client that accepts tcp/ip encapsulated serial 0183. You just can't p,ug one end into a bridge and load any old software on the PC.

That's all I was saying nothing more.

Given that navnet transfers radar and chart data , I fail to see how navnet is just encapsulated 0183

Dave
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Old 15-04-2013, 17:23   #15
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Re: NMEA into router

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No nick its not that simple , of you examine the encapsulated frames of many serial port severs , you will see subtle differences, some add prefixs or suffixes to identify sources ,etc. yes you can strip this away and you get a 0183 stream, but its either a virtual serial port software , back to back serial bridge or a client that accepts tcp/ip encapsulated serial 0183. You just can't p,ug one end into a bridge and load any old software on the PC.
You must be thinking this is a telnet server, but it isn't, they do straight TCP and UDP encapsulation, i.e. nothing is added or removed from the serial stream. Here is the manual: http://www.lantronix.com/pdf/EDS1100_EDS2100_UG.pdf

You actually can load any old software on any old PC and use this, as long as the PC has an Ethernet port and you install one of the virtual port drivers that supports TCP streams (they all do). I have used Eltima for this for many years, when I still used Windows Unix can do all this out of the box of-course.

Here is a document explaining how to use just a PC to feed NMEA to an iPad for navigation software. This is wireless, using the PC wifi adapter for the link: http://brookhouseonline.com/pdf%20fi...ipad_comms.pdf

Even though they use a PC here, they configure it just like a TCP device server that listens to port 5555 which can easily be setup with the GX2100 device server. The iPad has plain iNavX.

On Navnet: Radar, Sonar etc. are separate TCP streams that are established as clients request from the server. I mean the sensor data feed of-course (you knew that) which is just plain 0183 encapsulated in TCP. You find out the port number and you can tap into it with any PC and any old serial-port enabled app.

I had a major AHA moment when I got the data scrolling over my screen after using Google for the port number
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