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Discussion Starter #1 (Edited)
[NOTE: Before posting questions and responses to this thread, first read this other thread that gives more details of the completed project. Some of your questions might already have been answered.]

I am starting to buy the components (Seatalk cables, Seatalk/NMEA converter, baud rate converter) needed to get my instruments to talk to each other via NMEA. I would like to send the NMEA signal to a Netbook wirelessly via Bluetooth.

The most popular Serial-Bluetooth adapter seems to be one by IOGEAR (GBS301), but people complain that it does not support DTR/DSR handshaking. My RS232 skills are about 20 years rusty, and I'm brand new to NMEA, so I'd like to know if this will be a problem. Have any of you actually done NMEA over Bluetooth, and if so did you use the IOGEAR device?

Another device I'm considering is this, which offers the advantage of drawing its power from a USB cable:

Serial Bluetooth RS232 port adapter

Is anyone familiar with that one? Other suggestions?
 

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Discussion Starter #3

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BTW, NMEA doesn't support any hardware handshaking, so the IoGear's limitations shouldn't be an issue. :D NMEA 0183 doesn't support handshaking of any sort AFAIK.
 

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It should be fine. For practical purposes modern NMEA 0183 is a plain RS232 without any handshaking, any standard claims otherwise notwithstanding.

I see that its minimal baud rate is 9600. Rather than using a baud converter (which seems one moving part too many), why not pick another adapter that supports 4800 baud natively? Google brings up this: Wireless Serial Port - Wireless RS232 - Wireless Serial Cable Replacement - Bluetooth RS232 - LM058 - LM158 - BTD-433 - BTD-430

BTW, how do you power it up? I didn't find anything about power requirements in the spec.
 

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Discussion Starter #6 (Edited)
...I see that its minimal baud rate is 9600. Rather than using a baud converter (which seems one moving part too many), why not pick another adapter that supports 4800 baud natively? Google brings up this: Wireless Serial Port - Wireless RS232 - Wireless Serial Cable Replacement - Bluetooth RS232 - LM058 - LM158 - BTD-433 - BTD-430

BTW, how do you power it up? I didn't find anything about power requirements in the spec.
The IOGEAR does support 4800 baud - you just have to configure it with a terminal emulator instead of using the DIP switches. That's not why I have the baud rate convertor.

Sometime when I have more time I'll convert my hand-drawn schematic to a form that I can upload and show all of you. But in a nutshell, my first priority is to install the GX2150 VHF/DSC/AIS receiver that I recently ordered (and have not yet received) and interface it with my GPS/chartplotter setup. I also have a couple of SeaTalk instruments that I would like to interface so I can consolidate depth readings with everything else, and maybe to enable track-mode on my autopilot. But the Seatalk stuff is just "nice to have" not "must have," so if the conversion equipment ends up costing too much I'm not going to do that part of the project.

The new GX2150 improves on the GX2100 by allowing you to set the DSC input to 38,400 baud, so it multiplexes the AIS and DSC onto one port if you run at 38,400. (There are other threads on this topic.) But Seatalk only runs at 4800 baud. So using the baud rate converter to interface with Seatalk allows me to use only one Bluetooth port at 38,400 instead of needing two at different baud rates. It also eliminates a multiplexer, since Seatalk has its own built-in multiplexing capabilities by combining multiple instruments (in my case, depth and autopilot) into one Seatalk chain.

That Miniplex device is real nice because it combines multiplexing, Seatalk conversion, and perhaps baud rate conversion all into one device. But dealers are listing it at $400-700, and I've already found the BT and baud converters for about $20 each.

I can't find any specs on the IOGEAR's power requirements. It comes with a 120v AC adapter, but don't know if the adapter outputs 5v or 12v, don't know the amp draw, and don't know whether the connector is proprietary. The USConverters one runs off of a USB cable, which means it's 5 volts and less than 500 mA IIRC, and obviously there are 12v USB converters everywhere. So I'm leaning toward the latter because of the same power issues that you mentioned.
 

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That sounds pretty darn interesting :)

One point I am missing - so you have a 38K output from DSC/AIS and 4.8K output from Seatalk/NMEA. How do you put both those outputs onto a single bluetooth converter?

As an aside, what I'd really like to see is NMEA2000 to bluetooth converter. Literally raw data encapsulation - CAN bus packets minimally wrapped (length, magic number), sent over bluetooth for computer to read and process as needed. I am sure NMEA would never certify this - but who cares, that'd be a great way to interface software with NMEA2000 stuff. But I digress.
 

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Discussion Starter #8 (Edited)
That sounds pretty darn interesting :)

One point I am missing - so you have a 38K output from DSC/AIS and 4.8K output from Seatalk/NMEA. How do you put both those outputs onto a single bluetooth converter?
This gets to the part I'm not as sure about - I'll need to try it out. It depends on whether Seatalk echos or passes through NMEA sentences that it receives [EDIT: Seatalk Technical Reference says it does pass through NMEA sentences]. If so, it should work. My first try would be to feed the GPS sentences that come from the Bluetooth converter into Seatalk (using baud converter and Seatalk converter in series). Hopefully the Autopilot uses the GPS sentences that it gets from Seatalk, depth sounder adds its info onto the Seatalk chain, and the Seatalk converter then spits it all back out into the GX2150 input. The GX2150 uses the GPS coordinates for its DSC and for prioritizing the AIS readings, and spits out the DSC, AIS, and depth info to the Bluetooth converter, and it all makes its way to the chart plotter. [EDIT: Unfortunately this will not work as I described here. NMEA devices will receive sentences in and transmit their own sentences out, but they do not generally pass through the sentences that they receive. So I would need a multiplexer to do this.]

This is all a lot easier to follow in a schematic.

It's been a long time since I did serial interfacing, so I'll have to try it and see if it works. That's part of the reason I want to do it on the cheap, so I don't get stuck with a lot of expensive gear if I don't like it.

The other thing that I know will stir up a lot of controversy here is I plan to buy a RAM mount to put my Netbook in the cockpit. I'm a fair-weather daysailor, and did not get a drop of water in the cockpit last year. My Netbook is sitting virtually unused and has a matte finish screen that is incredibly bright - can see it easily in full daylight. And OpenCPN does a really nice display of AIS data. So I'll keep using my Garmin handheld as my primary device, but will have a bigger, brighter screen with AIS data on the Netbook. If it rains or starts splashing, I'll move the Netbook down to the cabin (Bluetooth will be nice for that) and just use the handheld in the cockpit like I did all last year.
 

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This gets to the part I'm not as sure about - I'll need to try it out. It depends on whether Seatalk echos or passes through NMEA sentences that it receives.
not as a general rule, and very unlikely to pass AIS.

The other thing that I know will stir up a lot of controversy here is I plan to buy a RAM mount to put my Netbook in the cockpit.
not from me :) nothing wrong with using a laptop as long as you take reasonable care and understand any potential limitations. though for obvious reasons my opinion on software selection would differ.


I got my netbook splashed a few times, thanks to wakes of passing powerboats. It's still doing ok.
 

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Discussion Starter #10 (Edited)
OK, here are two possibilities of what I might do. Note that a one-directional arrow represents a pair of wires for a half-duplex NMEA connection. Bi-directional arrows are Seatalk cables.

"Plan A" is what I attempted to describe above. If it works, it would interface depth, DSC, and AIS all to the chart plotter through Bluetooth, and also send GPS coordinates to the ST4000+ autopilot and radio. Note that there are two ways to send GPS to the autopilot connection: 1) wire it into Seatalk through the B&B baud converter and E85001 Seatalk converters into the ST30 depth gauge or 2) take it through the baud rate converter to the autopilot's NMEA input terminals. I denoted these two sub-options with dashed arrows.

I don't see a problem here with AIS getting to the Bluetooth adapter, because it is connected directly without going through Seatalk. The potential problem I see is that Seatalk may not pass through the GPS coordinates to the radio:


So if Plan A does not work, or I can't find the E85001 Seatalk converter for a price that I am willing to pay, this simplified "Plan B" arrangement should definitely work. It will not allow for displaying depth on my chart plotter, but the Seatalk cable between the depth and autopilot will allow display of depth on my Autopilot display panel. This is important because my view of the depth panel is frequently blocked by passengers in the cockpit, but the autopilot panel is much more conveniently located. It's a cleaner option that cutting a new hole and patching the old one to relocate the ST30 panel:

 

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Doc,

I used a Parani10
Parani 10
which seems to have been replaced by several other models such as
SENA Bluetooth Serial Adapter, Wireless Serial Device Server, Bluetooth Serial Module, Bluetooth Access Point, Bluetooth RS232, Device Networking, Serial Server, Bluetooth Dongle, Cable Replacement, Wireless Serial.

You can change its baud rate with a PC and setup program, I have used it at 9600 as well as 4800.

(no relation to either product or supplier, just used some at work and decided to try it on the boat). I also just noticed they have an RS485 version, which should be even "more" NMEA-0183 compatible..
.
 

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Discussion Starter #12
Thanks for the advice. I ended up going with the one from USConverters. It works flawlessly after I upgraded my Toshiba Bluetooth driver software in the Netbook.
 

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The Singapore pilots use a Bluetooth transmitter from IO gear. They connect a cable to the Pilot Port on the AIS, and to the bluetooth transmitter. Using the Pilot port they get all the GPS and AIS info plus heading from the ship's compass. Excuse me if I'm going off course; just thought it might be helpful.
 

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I'm using the same adapter to connect my HX851 portable with GPS to an ACER netbook running SeaClearII. I had trouble getting it to connect with the netbook (Win7 starter) so I tried an ACER laptop running Vista. This seemed to connect ok once Windows found and loaded the drivers. The blue light on the adapter came on solid instead of blinking. But Seaclear didn't update the position so I don't think it's hearing the GPS. Do you have any tips? I think I have the com port in Seaclear set to the same as the bluetooth adapter. The HX851 doesn't seem to have any settings. At least I couldn't find anything in the manual.
Thanks,
Jim
 

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It should be fine. For practical purposes modern NMEA 0183 is a plain RS232 without any handshaking, any standard claims otherwise notwithstanding.
To be clear NMEA 0183 is RS422, not RS232. It uses differential signalling, not ground based like RS232.
 

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Discussion Starter #16 (Edited)
To be clear NMEA 0183 is RS422, not RS232. It uses differential signalling, not ground based like RS232.
Technically you are correct, and if you wanted to make a 1000' run of wire without electrical interference it might be important. But over the distance of a a boat length (or much shorter in the case of using a short pigtail to connect a radio to a Bluetooth transmitter), RS232 works fine.

It seems like the common ground wire used in RS232 has become a de facto standard for this anyway. Standard Horizon uses a common ground for their NMEA transmissions (DSC + out, AIS + out, and GPS + in all reference the same common ground wire). It's impossible to follow RS422 if the electronic devices sending the NMEA sentences don't provide dedicated (-) wire for each (+) wire.
 

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Discussion Starter #17 (Edited)
I'm using the same adapter to connect my HX851 portable with GPS to an ACER netbook running SeaClearII. I had trouble getting it to connect with the netbook (Win7 starter) so I tried an ACER laptop running Vista. This seemed to connect ok once Windows found and loaded the drivers. The blue light on the adapter came on solid instead of blinking. But Seaclear didn't update the position so I don't think it's hearing the GPS. Do you have any tips? I think I have the com port in Seaclear set to the same as the bluetooth adapter. The HX851 doesn't seem to have any settings. At least I couldn't find anything in the manual.
Thanks,
Jim
There are about a dozen things that could be wrong. Hard to list them all.

First, NMEA standard is 4800 baud, 8 bits, no parity. Every link in your chain needs to be at the same setting. If your radio has no adjustable settings, chances are it is sending 4800/8/n. Your bluetooth adapter probably defaults to 9600, so you need to set it to 4800. Your Bluetooth receiver in your PC also needs to be 4800, and will send the transmission to a virtual COM port. That COM port is what your chartplotter software will see, and both need to be the same COM port and the same baud rate.

Your Bluetooth software may have a configuration utility that allows you to specify the COM port and baud rate. If not, go to Device Manager and select Ports, then the Port Settings tab to make adjustments. Native Windows Bluetooth support is notoriously bad, so you may need to go to third party software. Figure out whose Bluetooth transmitter is in your machine, and go look for their driver software online. I have a Toshiba chip in my netbook, and had to try 3 different versions of the Toshiba driver before I found the one that was 100% reliable.

Debugging all this took me a few hours. But once it's running, you never have to do it again.

Frankly, though, I would recommend that you just go buy a GPS puck to plug into your PC. In order for the HX851 to send/receive NMEA, it needs to be in its charging cradle, which is not weather resistant. And part of the whole purpose of having a handheld is to keep it out in the cockpit with you. So you'd be better off getting an inexpensive dedicated GPS puck for your PC. I got a Delorme LT-20 for $18, so they can be found cheap.
 

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Standard Horizon's NMEA 0183 seems to be particularly busted in general. I'm happy that there are alternatives to the GX2100 showing up on the market (like the Lowrance Link 8 and similar Simrad model) that don't require 3 unidirectional serial ports.

My Raymarine gear all uses differential signalling like RS422. I'm building some of my own NMEA 0183 gear now around a Netduino and decided to use RS422, not RS232, because the driver chips for either are roughly the same cost (about $1.50 or less each). For someone with basic hardware and software skills it wouldn't be hard to build a RS422 to Bluetooth repeater using Netduino or Arduino. There are pretty low cost bluetooth modules that will work with either platform. Having control over code in the middle will give you the flexibility to add in your own sensors, mux multiple NMEA 0183 inputs together, and otherwise control the data streams.
 

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Frankly, though, I would recommend that you just go buy a GPS puck to plug into your PC.
I agree. This is for backup to another wired GPS, and to help me learn about the networking technology. I'm not doing very well at that! Thanks for the help.
 

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Standard Horizon's NMEA 0183 seems to be particularly busted in general.
Why do you say that? Have there been lots of complaints? If it really is busted, then no amount of fiddling on my part will work. As I said in my first post, the computer claimed it was connected to the bluetooth adapter that's added to the radio. The adapter light stayed solid blue also, but the radio wasn't communicating with seaclear.

Jim
 
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