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Old 18-08-2017, 13:03   #1
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Problems With GlobalSat BU-353-S4 USB GPS and OCPN

I was just about to scream for help. I am running OCPN Version 4.4.0 Build 2016-05-31 on a Dell laptop with Ubuntu 16.04. I had bought one of these BU-353 USB GPS pucks before, and used it before with OCPN and Ubuntu, with no issues. It got misplaced somewhere and I recently bought the newer BU-353-S4 model. For just general navigation, I have not one but four Samsun Note 3 phablets, with good GPS capability, all rooted and running custom ROM, all unlocked, all with OCPN for Android installed. The problem was that the speed output displayed was not accurate enough and I could not change the averaging time or display refresh rate. This is normally no biggie but I was attempting to do some accurate SOG/RPM trials at low speed over short distances, to make power calculations easier, more relevant, and useful under varying conditions of wind and wave. I know that sounds anal, but my boat is electric, and I built the propulsion system and am continually tweaking it to get peak efficiency and performance out of it, so very small differences in Speed Over Ground vs prop RPM make a tremendous difference. I looked for the old GlobalSat BU353 and couldn't find it, and bought the new one, assured that the S4 variant was better.

I wanted to look at the raw NMEA sentences as they were output from the device, at low level, in a terminal, and both xgps (UI) and cgps (terminal) worked, as did GPSMON. I tried it with OCPN and it didn't work. The GPS debug window just showed gibberish or nothing at all. I did some research and discovered that Linux was allowing the GPS to "upshift" into SiRF binary output mode. I tried using gpsctl to change it back to NMEA 0183 output, but it didn't work. I borrowed a WinDOHs computer and installed the drivers from the supplied mini CD, but there was no option to change to or from NMEA. I found an older version online, SiRFDemo387.zip, installed that on the WinDOHs box, opened it and was able to find options for changing the device back to NMEA.

Meanwhile on my Ubuntu laptop I got rid of gpsd altogether using "sudo apt-get autoremove" in terminal. I don't really need the terminal based monitoring since I have the OCPN GPS Debug window for data. I set a filter of "VTG" so the window only shows NMEA sentences with VTG in them, which are velocity made good (Speed Over Ground, since no waypoint is specified on the device) in knots and km, and course in True and Magnetic. Each sentence is time stamped, too. I can easily take 10 or 20 sentences that look good and average them. I can also use the GLL sentence and average Lat and Lon over say a 60 second window, take the time from the middle of that minute, and then do the same at the end of the run, and manually calculate speed over the run to a high degree of accuracy and relevancy. Either way is going to work fine. The GPS itself is extremely accurate and fast! I can sit tied to the dock and the device sitting on the hatch, and after a few seconds it settles out and shows 0.0 knots. If I pick it up and move it an arms length away in a period of about two seconds, the speed spikes instantly, showing a knot or two. Extreme performance, much better than what the navigation panel of OCPN will display on either the Ubuntu or Android platform, or what any of the Android speedometer apps (I have tried at least two dozen different ones) will indicate. Performance indicated by the OCPN GPS NMEA debug window is slightly degraded below decks but still settles out to 0.0 knots for minutes at a time and detects movement of a couple of feet.

Another GPS device I bought since it was only about $12 was the DIY Mall G28U7FUSB, a bare naked USB device without a case. Performance below was not all that great plugged directly into the USB port below deck, but a little better with a 3' USB cable and almost as good as the BU353-S4 on deck with a clear view of the sky. The thing about the DIY Mall device is it apparently has no binary mode to shift into. I was able to use it with GPSD and the various related clients, even give it a network port (2497 I think is default) and it would run with OCPN. Unplugging, replugging, plugging into the WinDOHs computer, moving back to the Ubuntu computer, had no effect on it. So the GlobalSat GPS is a victim of its own sophistication. The simpler device costing 1/3 as much is much more practical, unless you are okay with running WinDOHs or Muckintosh.

Similar results with another USB GPS dongle I got free about 10 years ago with MS Streets and Trips, back before I was enlightened and introduced to the magical world of Linux. It was not as accurate as the other two devices, speed jumping around constantly, but never going over .3kts at rest. I think this is due to lack of DGPS/AGPS capability.

Now I know I have got a bit longwinded here, but basically I had a need that I thought the GlobalSat BU-353-S4 could answer for me, and it didn't, until I uninstalled gpsd using "sudo apt-get autoremove" in Terminal. So anybody else finding that the GlobalSat GPS, that comes so highly recommended for Linux, doesn't work, could get it running and playing nicely with OCPN by doing the same. Only drawback is that other apps that rely on gpsd for connection to a GPS might no longer work any more.

So, that still leaves me with the question of how gpsd can be made to play nice with this GPS, if it can at all. I did an extensive web search and the only clue I could find is that apparently the GPS will "latch" into SiRF mode, preventing Linux based tools from changing it back to NMEA, though the older version of the Windows software can always do it. Linux gurus... have you experience with this problem, and a solution, other than simply not using gpsd or the gpsd clients?

Before anybody asks what this has to do with OCPN, remember that the device will no longer work with OCPN when it is latched into SiRF mode. It must be in NMEA mode. I want it to stop making itself unreadable by OCPN just because I have gpsd installed, which I believe is part of the stock Ubuntu 16.04 distribution.
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Old 18-08-2017, 16:16   #2
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Re: Problems With GlobalSat BU-353-S4 USB GPS and OCPN

Quote:
Originally Posted by GrowleyMonster View Post
I borrowed a WinDOHs computer
Love it !!! I normally call it windoze but WinDOHs sounds even better
Anyhow, to the subject at hand, it's been a long time and longer than the standard 24 hrs that my brain at my age is capable of so I can not give you the details other than to say that google is your friend. I ran into the exact same issue, googled for a result, found it (I think it only needed switching once) and haven't thought about it since then.
Good luck!
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Old 25-08-2017, 12:08   #3
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Re: Problems With GlobalSat BU-353-S4 USB GPS and OCPN

I seem to have the BU-353-S4 USB GPS working pretty good now. I edited the file "etc/default/gpsd" and that initially didn't seem to help. I went back and forth to the neighbor's WinDOHs computer and put it back into NMEA mode a couple of times. I was starting gpsd using the -b and -n switches as in:

sudo gpsd -b -n /dev/ttyUSB0

and finally it started behaving. There were a couple of reboots involved and I think that might have been what did it. I found the speedo I was looking for in xgpsspeed, one of the gpsd clients. I started it with

xgpsspeed --nautical --maxspeed 4

which sets it into nautical mode and sets max speed on the GUI to 4kt. Xgpsspeed is an x windows presentation. The plain vanilla mode is kinda plain. Nautical mode gives a lot more information. You get the speed at the bottom and a speedometer dial with a direction thingie in the middle, and an overlay of satellite positions.

Here is the content of my "etc/default/gpsd" file:

# Beginning of file gpsd. Use # to comment.
# Default settings for the gpsd init script and the hotplug wrapper.

# Start the gpsd daemon automatically at boot time
START_DAEMON="false"

# Use USB hotplugging to add new USB devices automatically to the daemon
USBAUTO="true"

# Devices gpsd should collect to at boot time.
# They need to be read/writeable, either by user gpsd or the group dialout.
DEVICES="/dev/ttyUSB0" #I changed this. Supposed to work better.
# GPSD_OPTIONS="/dev/ttyUSB0"
# DEVICES=""

# Other options you want to pass to gpsd
GPSD_OPTIONS="-n -G -b"
GPSD_SOCKET="/var/run/gpsd.sock"
# End of file gpsd

OCPN works great with this GPS now, but to be safe I always start the GPS using gpsd, and check for output using gpsmon. The accuracy and speed of the device is stunning, and accessing it at a low level using the gpsd clients such as cgps, xgps, and gpsmon is quite revealing. xgpsspeed seems to work really well as a fast, responsive, somewhat flexible, easy to read speed indicator. However I would urge any new user to explore the other gpsd client applications, too.
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Old 25-08-2017, 12:25   #4
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Re: Problems With GlobalSat BU-353-S4 USB GPS and OCPN

Oh, a few more thoughts related to running OCPN with this GPS and gpsd in Linux.

I find a network connection works better in OCPN than a plain vanilla USB connection. Using a network connection also allows use of one of the gpsd clients and OCPN at the same time. To set this up, in Options go to Connections Uncheck any connections already listed. Click "Add Connection". Select "Network" and then for protocol select "GPSD". Data Port should be 2947. Priority 1, and checkmark "Control Checksum", and for input filtering select "Accept only sentences". That works for me, anyway. Then click "Apply" down at the bottom. In the main Options/Connections dialog, make sure that the new Net connection on localhost:2947 is checkmarked and no others. To see the raw GPS sentences, checkmark "Show NMEA Debug Window". You can pause it and copy to a text file if you want to average out a position or speed, then close it to return to Options. Hit "OK" to close it and you should see the GPS indicator showing green bars and an accurate Ship Position displayed at the bottom status bar, and SOG/COG showing after enough position updates.
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Old 27-08-2017, 02:59   #5
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Re: Problems With GlobalSat BU-353-S4 USB GPS and OCPN

Growley, This is an excellent post. Do you think it should be in the manual or not? If so could you provide a title, text and a few necessary screenshots? Just post in this thread.
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Old 27-08-2017, 08:46   #6
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Re: Problems With GlobalSat BU-353-S4 USB GPS and OCPN

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Originally Posted by rgleason View Post
Growley, This is an excellent post. Do you think it should be in the manual or not? If so could you provide a title, text and a few necessary screenshots? Just post in this thread.
You mean the OCPN manual? Since this GPS is such a cheap and convenient option and has such a nice chipset in it, I think detailed instruction on setup for Linux computers would be a good idea. However, my results are maybe too preliminary for inclusion in the official manual until a few other people have tried and refined the method, I think. At this point I can't be sure that all of the steps I performed were necessary, or that they would be common to all computers running Linux or even just Ubuntu Linux. And if I REALLY knew what I was doing, I would not have needed to start the thread in the first place.
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Old 27-08-2017, 12:56   #7
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Re: Problems With GlobalSat BU-353-S4 USB GPS and OCPN

I can post your writeup with that caution, asking for improvemwnts. At least its something.
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Old 27-08-2017, 12:57   #8
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Re: Problems With GlobalSat BU-353-S4 USB GPS and OCPN

Yes, i do mean the user manual.
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Old 27-08-2017, 14:44   #9
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Re: Problems With GlobalSat BU-353-S4 USB GPS and OCPN

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Originally Posted by rgleason View Post
I can post your writeup with that caution, asking for improvemwnts. At least its something.
Okay you are certainly welcome to use any of my posts as you see fit, and I will try to consolidate everything eventually with some screen shots, understanding of course that you may well need to make a correction here or there or remove something that is later proven unneccessary. I didn't start the thread offering expert advice, but rather asking for it. I just gave my one remaining spare laptop to my GF because she wanted to try Linux, but I might be buying a new one soon, which will have to be set up the way I have this one set up. That will give me a fresh lab rat to experiment with.
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