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Re: Attempting to access the GD-8200 GPS

From: Stuart Blake Tener
Subject: Re: Attempting to access the GD-8200 GPS
Date: Sun, 17 Jul 2022 01:45:17 -0400
User-agent: Horde Application Framework 5

Gary, et alia:

Make no mistake that I take no offense to "Yo Stuart!" but I would be a bit upset if someone called me a yo-yo! :)

Thanks for finding the manual, I already started reviewing it. I did order a replacement GPS board on eBay for my laptop for a whopping $6.77, so, all out replacement is an option. However, I am not so sure I have a hardware problem...

I took your advise and took the laptop outside, right at about the 13 minute mark satellites started to pop in on cgps' display. One, then two, then, bang 9 of them! I did not realize it could take 12 to 30 minutes to obtain the almanac and ephemeral data, next time I will be far more sensitive to that fact. Moreover, the last outdoor test I did I was driving around with the laptop sitting in my front passenger seat. This time, I sat outside by the pool in my backyard with laptop sitting still on the table.

It is remarkable that whence I returned into the house the number of satellites that the GPS receiver could hear diminished briskly and cgps even put "na" where the longitudinal and latitudinal data was for a few seconds then refilled it back in (this kept happening back and forth). This may be due to a poor antenna connection on the GPS, perhaps a problem with the receiver, or just that part of my house is a Faraday cage (I used to get zero mobile coverage in my master bedroom nor could I hit any ham repeaters in there, but step outside the open door and things improved). The indoor GPS testing was done in my dining room, where my mobile phone has always worked fine. I also will make sure my configuration specifies that this receiver is based on a SiRFstar III chip too.

Putting PPS to the side, what do you recommend as a newer more quality USB GPS to use today? By the way, my computer does have a DB-9 serial port on it too, though they make USB to DB-9 serial cables these days too. What do you think of the "GlobalSat BU-353-S4" USB GPS?

Getting the GPS working on my laptop was kind of an ok, it is there, why not make it work or replace it? However, having a decent GPS I can plug into one of my servers to give me GPS time would be nice. I will ask if anyone has successfully setup gpsd and chrony so that it uses GPS time primarily and USNO NTP servers secondarily?

By the way, the autobaud did not work when I conducted the "inside my house tests". However, I will re-test my gpsd configuration parameters outside also (with autobaud), just to see if that is an issue. For now, gpsd starts with the '--speed 4800' parameter provided.

Incidentally, page 11 of the manual you found does seem to stand demonstrative of the different pins the GPS receiver uses and for what. Perhaps it will be possible for me to pin them out and "trace the traces" on the board so I can identify what pins on the interface cable go to what functions on the receiver. Then it might be possible for me to get a newer receiver board and interface it to the laptop. I imagine using a USB based GPS would be easier though. I also noticed that this GPS receiver board does have PPS output on it too. For what it is worth "/dev/pps0" does exist. More "/sys/devices/virtual/pps/pps0" directory exists with a bunch of stuff below it too.

As far as a GPS for time service, what do you recommend hardware wise (presuming I have a serial port available, or I/O pins on a Raspberry Pi or the like)? If I put a hat on a Raspberry Pi for that purpose, I'd want to try to be sure it had a connector on it so I could have an external (outdoor) antenna.

About SystemD...

I am not interested in a religious war over SystemD, as I am not armed for such combat. I do know that the init scripts of UNIX and Linux were a very aged and in some cases transmogrified methodology, replacing them with a better mechanism was far overdue. SystemD has never given me a problem and I have been able to use it to start/stop/restart/reload, etc... system services many times for a long time. That said, I have never immersed myself in the "SystemD hate debate", as I do not know it on such a deep level to have an opinion on it. I learned it, I use it, and it has never been a problem for me. However, I will read a bit about why people hate it so much, though I am curious, when I do my research, how many of the people that hate SystemD have ever contributed code to fixes to anything or started working on an alternative?

Thank you for all your thoughts and assistance and I pray you stay healthy and safe from the thugs.


Very Respectfully,

Stuart Blake Tener, BScCS, N3GWG (Extra), MROP
Computer Scientist / FCC Licensed Radio Operator

Las Vegas, NV / Philadelphia, PA

(310) 358-0202 Mobile Phone
(215) 338-6005 Google Voice

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