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NMEA over Bluetooth

30K views 35 replies 7 participants last post by  TakeFive 
#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?
 
#2 ·
#3 ·
No reason not to, if I were willing to pay 20x more for their device instead of using commodity computer equipment.
 
#4 ·
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.
 
#5 · (Edited)
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.
 
#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.
 
#7 ·
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.
 
#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.
 
#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:

 
#11 ·
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..
.
 
#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.
 
#13 ·
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.
 
#14 ·
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
 
#17 · (Edited)
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.
 
#18 ·
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.
 
#20 ·
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
 
#22 ·
The GX2150 fixed the primary issue of requiring 3 unidirectional ports (1.5 bidirectional) because it needed a mix of 4800 and 38400 when talking to some devices. The GX2150 is also a lot of money though.

The Lowrance Link 8 appears to have the same basic feature set, doesn't have the NMEA headaches of the GX2100, and is less money than the GX2150 (or even less than the GX2100 was when it was being heavily discounted).

The Simrad RS35 is about the same price as the GX2150, but has the option of a nice wireless remote mic.

Both also talk NMEA 2000 (CAN Bus), not only 0183 (RS422/RS485/hacked RS232).
 
#25 ·
It's not just NMEA 0183 vs NMEA 2000, it is their weird choice to have two output ports on the radio, one of which sends different sentences then the other. They "fixed" that on the GX2150 if you configure it at 38400. If you configure it at 4800 then one port talks 4800 and the other talks 38400, and they each send different sentences.

To work with your bluetooth adapter (which only has one serial input line) you'd need to configure the radio at 38400. If you configure it for 4800 then you won't get the AIS sentences, only the DSC ones. This is on page 16 of the manual.

Their NMEA 0183 implementation is weird in many respects. That doesn't mean that the device doesn't work, it does when properly interfaced. They just made it harder than necessary to interface with it. I'm glad that they invented the market segment, and I'm glad that other companies are coming out with better options in this market segment.
 
#26 ·
It's not just NMEA 0183 vs NMEA 2000, it is their weird choice to have two output ports on the radio, one of which sends different sentences then the other. They "fixed" that on the GX2150 if you configure it at 38400. If you configure it at 4800 then one port talks 4800 and the other talks 38400, and they each send different sentences.

To work with your bluetooth adapter (which only has one serial input line) you'd need to configure the radio at 38400. If you configure it for 4800 then you won't get the AIS sentences, only the DSC ones. This is on page 16 of the manual...
You are reading the wrong manual. This guy has a HX 851. You should do your homework before misleading him any more.

As for the GX 2100, your argument that sending different sentences outputs is incorrect. I have it working perfectly with 2 Bluetooth adapters. Click the link that I showed above to see how.
 
#27 ·
I'm sorry to cause confusion about the HX 851. I missed that part and saw references to the GX21xx. I've never looked at the HX 851.

You are using 38400, which I noted does send all sentences out of one NMEA port. At 4800 it does not. This is covered in the GX2150 manual on pages 16 and 17.
 
#28 · (Edited)
...You are using 38400, which I noted does send all sentences out of one NMEA port. At 4800 it does not. This is covered in the GX2150 manual on pages 16 and 17.
I have NOT configured my GX2150 in the way you say. The GX2150 gives you the option of multiplexing both AIS and DSC onto one wire (the gray one) at 38400. But you do not have to do that. You can instead opt to send the signals out the same way as done the GX2100, with DSC/DSE on the grey wire at 4800 and AIS on the brown wire at 38400. That is how I have my radio set up, and it has been working perfectly fine with my computer chartplotter for the past two years. The reasons I chose to do that are complicated and I don't have time to explain right now. But bottom line, I could plop your GX2100 into my boat and it would work in exactly the same way. Contrary to what you say, I am not currently taking advantage of the GX2150's option to multiplex DSC and AIS onto one port.

As for this guy's HX851, he simply needs one full duplex COM port, probably at 4800 (since his manual does not list any options). The GPS sentences simply go out the charging cradle to the Bluetooth adapter, which gets mapped to an emulated COM port in his computer.
 
#30 ·
You are also going to have to do some research into DCE vs. DTE modes so you'll know how to set the switch on your adapter. I cannot remember which setting is correct for this device to work properly, and my adapters are down on the boat. These are some of the more cryptic aspects of RS232 communications, and I only learn them long enough to configure my new gadgets once every 10 years or so.
 
#34 ·
I was talking about the GX2100 being broken by having two output signals with different NMEA sentences at different baud rates. Having the input be at 4800 and the output be at 38400 isn't that weird (outside of PCs) and isn't the GX2100 concern that I raised.
 
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