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Old 06-08-2011, 15:55   #1
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GPS into VHF Radio from PC Running OpenCPN with USB Device ?

I read the new VHF have a feature where they broadcast your positon in distress calls?
I have an onboard PC running opencpn, ubuntu 11.04, uses a delorme lt-20 usb for the gps data. I just set this up today at home to get it working.
so how do you output gps data to the radio or other electronic things?
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Old 06-08-2011, 16:32   #2
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Re: gps into vhf radio from PC running opencpn with usb device?

OpenCPN is not able to forward/relay GPS NMEA data, unless you can get a RMC string from the Autopilot output. You need to edit the opencpn.conf file to enable RMC on that port. RMC can be read by the VHF.

This is not a good solution. As DSC is a safety feature I would suggest that you put some mony in to buy a good stationary GPS (e.g. Furuno GP-33) or a SMART GPS antenna (without display).
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Old 07-08-2011, 18:06   #3
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

An alternative is to use a dedicated GPS wired into the DC supply (I use a garmin map76 for this) and connect the output to a common terminal strip creating your own GPS bus. Any GPS unit will feed three listeners max without a multiplexer or anything fancy. So the GPS unit can feed the putter, the radio and one additional device as needed. The computer connection via USB was a bit tricky to get the wires correct, (boat is a days drive away) but it can be done.

Its good to have at least two GPS talkers on board at all times.

/ch
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Old 07-08-2011, 20:42   #4
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

Quote:
two GPS talkers on board at all times
yes I think that is true.
The USB Delorme LT-20 I got on Ebay for $14 and so far seems to work ok.
Also, If you call on your cell phone and it has a gps, then they know where you are.
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Old 08-08-2011, 01:21   #5
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

Quote:
Originally Posted by sailias View Post
The computer connection via USB was a bit tricky to get the wires correct
USB to Serial adapter and then a plain 9 pin plug with NMEA + and - connected to pin 5 and 2 (where pin 5 is common/minus and 2 is RX plus).
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Old 08-08-2011, 20:29   #6
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

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Originally Posted by HotRod View Post
USB to Serial adapter and then a plain 9 pin plug with NMEA + and - connected to pin 5 and 2 (where pin 5 is common/minus and 2 is RX plus).
That will work if you go directly from the device, but not if you build a gps bus. You are dealing with bare wires. One the computer side these are best connected to a usb male fitting as most laptops do not have a serial port. USB/Serial port converters are prone to failure due to the nature of the OS used. Mine for example will at times show up as a trackball when I use windows.

What I meant by 2 GPS talkers is two stand alone units. Its a safety factor and they are relatively cheap. A USB device is not a safety backup nor is a phone, loose the putter and your down, loose the connection on the phone and your down. Also these are useless in the ditch bag. Best to have two takers that run on batteries. One installed on the GPS bus and one in the ditchbag as backup.

/ch
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Old 08-08-2011, 23:12   #7
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

If you really want to hook up your radio to the computer use Eltima VSPE (Eterlogic - VSPE: tool for serial ports emulation) (free!) to spilt your incoming GPS signal to two ports, one to openCPN the other to the radio through a serial to USB convertor (about $5 on ebay)

Despite the naysayers this can work reliably.

BTW serial Serial to USB convertors connected to GPS units can sometimes show up as a serial mouse -it's a Windows problem, to stop this (mentioned above) use pnpblocker
http://www.stentec.com/anonftp/pub/w...ockersetup.exe and block mouse detection on the com port your GPS uses. This is a great solution to a very annoying problem!
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Old 09-08-2011, 05:06   #8
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

There are two issues here, first and foremost safety, secondly design. From a safety perspective a laptop of computer is too unreliable a piece of equipment to be the distribution point for a GPS signal. Its subject to failure from water, moisture, hardware and software. A GPS talker that is a standalone unit is far more reliable. This does increase the level of complexity however in how the signal is distributed. The solution for my boat was to build a standalone GPS bus where the talker is a dedicated unit that can be replaced by a backup unit as needed. The laptop will eventually be redundant as well as budgets allow. An alternative more costly route is to use a multiplexer, it accomplishes the same function a gps bus. As everything is hard wired the only failure points are the pieces if equipment the GPS is feeding. This is standard however.

YMMV....best of luck.

/ch
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Old 10-08-2011, 07:18   #9
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

If you decide to skip the USB-Serial adapter and just solder it onto a usb plug, don't turn to me if your gps or computer stops corresponding on your usb ports or that the devices die...
In my proffession i have seen this happen many times.
There is no protection what so ever on your usb ports when connecting it directly.
With a USB-Serial you will only damage the USB adapter - but this does not stop surges. Then you need a opto isolator in addition.

Buy a ATEN UC-232A USB to Serial adapter (These are really reliable).
For extra protection use Actisence Opto-3 opto isolator.
These in combination are the most common setup that we deliver to our business customers and private customers.

Never problems with these setups. But usually when we deliver a system, we use computers with serial octopussy interfaces.

Stay trouble free, don't re-invent the wheel again...
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Old 10-08-2011, 07:23   #10
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

Not to start a rant as this is a good solution for what it does. However if the computer fails and is the relay point for the radio you are SOL. Hence IMHO the weakest point in using a computer as a multiplexar is the computer itself. Hence mine is only one listener of three and not a talker.

Best regards

/ch
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Old 12-08-2011, 09:48   #11
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

+1 on sailias comments, plus I will add mine, I wanted to log the openCPNīs output at the autopilotīs com port, and I realized that you need to have an active waypoint or route for RMC sentence to appear, otherwise (no waypoint no route) there will be no position data outputting. This sums up another problem to an already convoluted task, you have to remember to activate a waypoint even if you dont want to, just to get LL into the VHF.
Just for reference this is a small log:

NMEA log from 11/8/11 12:30
$ECRMC,152916,A,3358.573,S,05801.881,W,5.000,315.0 00,120811,-0.000,E*45
$ECRMB,A,0.033,L,001,,3357.798,S,05802.913,W,1.155 ,312.165,5.000,V*2E
$ECRMC,152917,A,3358.572,S,05801.883,W,5.000,315.0 00,120811,-0.000,E*47
$ECRMB,A,0.033,L,001,,3357.798,S,05802.913,W,1.153 ,312.162,5.000,V*2F
$ECRMC,152918,A,3358.571,S,05801.884,W,5.000,315.0 00,120811,-0.000,E*4C
$ECRMB,A,0.033,L,001,,3357.798,S,05802.913,W,1.152 ,312.159,5.000,V*26
$ECRMC,152919,A,3358.570,S,05801.885,W,5.000,315.0 00,120811,-0.000,E*4D
$ECRMB,A,0.033,L,001,,3357.798,S,05802.913,W,1.151 ,312.155,5.000,V*29
$ECRMC,152920,A,3358.569,S,05801.886,W,5.000,315.0 00,120811,-0.000,E*4C
$ECRMB,A,0.033,L,001,,3357.798,S,05802.913,W,1.149 ,312.152,5.000,V*27
$ECRMC,152921,A,3358.568,S,05801.887,W,5.000,315.0 00,120811,-0.000,E*4D
$ECRMB,A,0.033,L,001,,3357.798,S,05802.913,W,1.148 ,312.148,5.000,V*2D
$ECRMC,152922,A,3358.567,S,05801.889,W,5.000,315.0 00,120811,-0.000,E*4F
$ECRMB,A,0.033,L,001,,3357.798,S,05802.913,W,1.146 ,312.145,5.000,V*2E
NMEA log to 11/8/11 12:30

regards. alex
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Old 12-08-2011, 14:56   #12
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

if your running linux, the output is there all the time on device
/dev/ttyUSB0
using gpsd daemon it outputs gps data realtime to all programs at once.

I can run openCPN along with foxtrotgps and xgps and all the programs work together realtime. Is handling gps port data on windows different? like can only one program get gps data at a time?

FoxtrotGPS - the friendly FOSS GPS
The xgps client
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Old 12-08-2011, 17:04   #13
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

Here I can only have one app receiveing GPS signal (at the same com port), as soon as I fire Ozi and try to connect it says it cant open COM port. have to close OCPN and then I can reconnect with Ozi. So I guess only one program has it at a time. That you could solve with VSPE and creating a Splitter so they both can take signal.

I use Ubuntu 10 but navigation is done on Windows for compatibility with my job.

I meant there is output from OCPN only when you activate a w/route. Otherwise the output stays blank, after all it IS an Autopilot output . This has no relation to the COM distribution priority but to OCPN procedures I think. The Linux gpsd daemon seems to bridge the GPS through the com port (ttyUSB) but then I would understand you dont need to include RMC in the .conf file, dont you?
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Old 12-08-2011, 19:43   #14
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

that is interesting the com port is locked to the program when it runs?
So windows cant multitask this.

No such problem in linux.

Quote:
but then I would understand you dont need to include RMC in the .conf file, dont you?
I guess no. I really dont know how to hook hardware device up to a linux box and then output that data from a port to that device. But I can figure out a lot of things given enough time.

Quote:
gpsd is a service daemon that monitors one or more GPSes or AIS receivers attached to a host computer through serial or USB ports, making all data on the location/course/velocity of the sensors available to be queried on TCP port 2947 of the host computer. With gpsd, multiple location-aware client applications (such as navigational and wardriving software) can share access to receivers without contention or loss of data.

Also, gpsd responds to queries with a format that is substantially easier to parse than the NMEA 0183 emitted by most GPSes. The gpsd distribution includes a linkable C service library, a C++ wrapper class, and a Python module that developers of gpsd-aware applications can use to encapsulate all communication with gpsd.
What do you think 'TCP port 2947 of the host computer' is saying?
That this is an open port that a separate device could query and get gps data from?
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Old 12-08-2011, 20:17   #15
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Re: GPS into VHF Radio from PC Running OpenCPN with USB Device ?

For testing purposes on linux this is good. Windows cant deal with mutiple com connections natively, you need to setup virtual com ports. Both with linux and windows, I prefer to have the gps talker on its own and the putters and all other listeners services by the talker. Its a really simple setup. Any GPS talker can provide data to three devices max. Same for AIS data...comming from newer radios...just setup a separate bus (hard wire) and connect it to a terminal strip and hang three devices from that strip. Its a very safe way of doing things onboard where nav data is considered at least in my book as mission critical.

Linux can do far more natively out of the box then window as its sees the com ports simply as devices. So it can listen to many devices and do with the data as you tell it too as you have experienced. The issue in a marine environment is if the putter is a talker it can fail on the hardware side and it takes quite a while to reset your system once your used to that setup.

Having a simple AIS and or GIS bus (wired) allows you to replace any talker and any listener simply and easily provided you have the needed replacement. Hence on my boat, I duplicate all aspects of the nav and communications systems. Should you suffer a hardware failure from a variety of sources, you have backup. Just bring the secondary on line, thats about it. Everything else stays the same. Cant do that if the heart of the system is the putter......even if its cloned on daily basis which rarely happens at sea...its not an IT shop environment..

Best of luck regardless of what route you choose.

/ch
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