Connecting laptop to Garmin Network

[rleslie]

I am buying new nav equipment for my boat - am looking at the Garmin 3006. Can I connect the Garmin device(s) to the ethernet network on my boat (and therefore my other computers on board)? Or is the Garmin network proprietary and therefore requires me to connect directly from the computer to the Garmin devices?

[exposure]

Garmin uses ethernet for the hardware standard, but I theink they use their own protocol for communications. I think you are out of luck unless they make an adapter of some kind. I suspect you would not want to mixe the two data systems on the same wires as they would probably interfere with each other.

[jurek]

Hello,
I would like to refresh this topic.
My goal is to connect Garmin GSD 26 Sounder with laptop and use laptop to listen and control this device. I prepared Garmin Marine Network -> RS232 -> USB interface and download Advanced NMEA Data Logger and Advanced Serial Data Logger, but I am not able to listen and control my device. My question is if you have any advice connected with this problem or if you ever solve similar problem.

My way of thinking is as following:
I assumed that Garmin is using standard pinout of ethernet (RJ45) with crossover like here:
http://static.garmincdn.com/pumac/Marine_Ethernet.pdf
Then I connect my RJ45 cable with RS232 interface according to:

(thick lines mean necessary connection and thin lines - additional). Bearing in mind that sent protocol is not an ordinary ethernet signal, but the NMEA signal, Rx and Tx cables are not connected directly, but by the translator, according to the scheme:

(NMEA R means RXD pin from RJ45 cable etc.).

After those modification I connected this interface with my laptop, using RS232->USB cable. I was trying to listen my signal with Advanced NMEA Data Logger and Advanced Serial Data Logger (there are available here:
Advanced NMEA Data Logger | Free download | AGG Software
Serial Data Logger Software - serial data logging from Serial, COM, RS232, RS485, RS422 ports to a file, Excel or a database | AGG Software )
but I am not able to listen anything.

Do you have any idea how to solve this problem?

[muttnik]

Originally Posted by jurek

My goal is to connect Garmin GSD 26 Sounder with laptop and use laptop to listen and control this device. I prepared Garmin Marine Network -> RS232 -> USB interface and download Advanced NMEA Data Logger and Advanced Serial Data Logger, but I am not able to listen and control my device.

Disclaimer: I really don't know anything about Garmin's Marine Network, but as no-one with more knowledge has replied I think I can take a guess at some of the (several) things that might be wrong with this picture.

I think the issue is that you are expecting the network to carry serial data in an NMEA-0180/NMEA-0182 (or NMEA-0183) format as indicated by your "NMEA to RS232" diagram and choice of data logger software. I don't believe that this is the case. exposure stated in post #2 that it was ethernet at the lower protocol layers. At higher layers the data will be encapsulated in a non-public proprietary format. It might be that data other than sonar imaging data is carried in an nmea-style format *within* that encapsulation (perhaps a Garmin expert here could tell us?) but my guess would be that that would be more likely to look like NMEA-2000 than NMEA-0183.

The first problem here then may be assuming that the wire carries serial data. Whilst RJ45s are used for serial connections to, for example, console ports of some servers, routers and switches, your wires here are not used for serial data: it's ethernet so you can't wire it to a DB9 and read it like an RS232 connection.

The data format I already mentioned: almost certainly not what you are expecting to read.

Someone else here may have a better plan but presumably you have your sonar connected to a Garmin MFD (plotter or whatever you call it) to display the imaging data. If so check the manual to see if it does data bridging and has an nmea-0183 output. If so, leave the sonar connected to the MFD and take the data feed from the nmea-0183 output to the laptop. You obviously won't get imaging data, but it might do depth (and other sources might give you position).

About that "NMEA to RS232" circuit though...lose that. I'm no electronics expert but that looks to be converting between TTL and RS232 which may be from pre-NMEA-0183 times (even before the first -0183 iteration which would have been happy with RS232). More recent NMEA-0183 iterations will be opto-isolated and be putting out (differential) rs422.

[jurek]

OK, I understand and really thank You for your answer.

The thing is that I would like to avoid to connect my sounder with Garmin MFD. I want to replace it by laptop.
As I know, there are some types of MFD which allows to connect also by USB, but anyway they are not able to control sonar in way which I need.
Everything what I need is to get information about distance to obstacles (I do not need images) and to control sent signal - I need to send the signal and then observe the response of system with sonar - basically I need this time (or distance) signal.

As regards to serial data, the biggest problem is that I am not able to find reliable information about used standard, so I am basing on assumptions. I know that previously they where using NMEA-0183 and connection of this standard where quite good described, but now - there is a lot of question without answers (or just I was looking for in not good places )

Anyway thank's for advice - I would try to find another way of connection.

[smac999]

so you joined a rj45 Ethernet plug to a serial port?......


I highly doubt garmin is sending serial comms let alone nmea 183 throught it's network cables. it would be network layers and protocols.


it would go into your computer network port. but I doubt you could decode it. maybe someone could


I also highly doubt it's sending out any transducer timing or control info. the only thing coming out would be depth picutres and data use by the mfd


if you are actually looking for ping data etc you would have to tap into the box itself. more likely make your own black box souder.



I'm also not sure what the converter is for. nmea 183 is already serial based and can be read direct by a computer. (if the data was nmea 183) I'm thinking it might be a 422 to 232 converter. and poorly named a nmea converter. because nmea can come in both forms. but I've never needed one to read either form of nmea before.

[jurek]

I think serial port in my GSD26 is exactly RJ45 port I do not have any more serial ports in this device. I had only place to connect transducer and temperature/velocity sensor. Last plug is for power supply. So I don't have nmea-0183 socket and cable.
I was trying to directly connect GSD with my computer by rj45 cable from Garmin, but computer cannot see this connection and even diode (when I was checking in PC computer) is not switched on. I checked - voltage on cable is present, but I suppose that pinout is just different than in computer.

I hope that depth pictures are based on depth information - they must create them somehow as I understood correctly, NMEA protocol is based on ASCII text, so I can find interesting information inside

Maybe it will be necessary to find something inside sounder. And abandon converter - just find right pinout of cable.

Thank You!

[muttnik]

Originally Posted by jurek

I think serial port in my GSD26 is exactly RJ45 port

I think that in this case the RJ45 is an ethernet port, not a serial port. This is commonly the case on both radar and sonar units these days. The higher bandwidth of ethernet over a normal serial line facilitates the transmission of imaging data.

I was trying to directly connect GSD with my computer by rj45 cable from Garmin, but computer cannot see this connection and even diode (when I was checking in PC computer) is not switched on. I checked - voltage on cable is present, but I suppose that pinout is just different than in computer.

If the Garmin Marine Network is 100baseTX (i.e. the most common fast ethernet) and your computer's ethernet port is the same you'll need a crossover ethernet cable to get a link. I don't know how Garmin deals with the network layer and address assignment but if you're interested in pursuing this I'd suggest you might be able to get some clues from the source to the OpenCPN Garmin radar plugin: it's probably similar.

I hope that depth pictures are based on depth information - they must create them somehow as I understood correctly, NMEA protocol is based on ASCII text, so I can find interesting information inside

That GSD26 of yours will have done some complex image processing to build a picture from the transducer information. Images from sonar and radar tend to be passed between devices using proprietary protocols, not NMEA ones. Note also that the current (NMEA-2000) and forthcoming (NMEA OneNet) protocols are not simple ASCII strings either.

If I were looking to learn about the sonar data format I'd familiarise myself with the source of the previously mentioned OpenCPN gradar plugin as a starting point as the radar implementation might have a lot in common with the sonar, although that's just a guess.

Good luck: You can always send a message to Garmin technical support: They are unlikely to tell you much about the data format but they might confirm things like the Garmin Marine Network being based on 100baseTX and that the GSD26 sends out image data, not a series of NMEA-0183 DBT sentences.

[jurek]

Thank You very much!
So I have some possibilites to try
I would let know what I found out.

Thanks!