From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.perfora.net (mout.perfora.net [74.208.4.195]) by huchra.bufferbloat.net (Postfix) with ESMTP id C5FD120036C for ; Sat, 17 Mar 2012 14:31:59 -0700 (PDT) Received: from [192.168.83.5] (c-76-97-152-51.hsd1.ga.comcast.net [76.97.152.51]) by mrelay.perfora.net (node=mrus4) with ESMTP (Nemesis) id 0MGAm7-1S3qhw2gyN-00EmCN; Sat, 17 Mar 2012 17:31:58 -0400 Message-ID: <4F6502CA.4020507@c3energy.com> Date: Sat, 17 Mar 2012 17:31:54 -0400 From: "Ron Frazier (NTP)" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.9) Gecko/20100722 Eudora/3.0.4 MIME-Version: 1.0 To: questions@lists.ntp.org, "thumbgps-devel@lists.bufferbloat.net" References: <20111025095801.C9A9D800037@ip-64-139-1-69.sjc.megapath.net> <4F64DCB8.7090603@c3energy.com> <004801cd0476$7e4fe670$7aefb350$@ch@verizon.net> In-Reply-To: <004801cd0476$7e4fe670$7aefb350$@ch@verizon.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V02:K0:AKgS0Fr9crvtj1bV+r6Aaep7ihImpayh3V8waC4HyG0 cXLDmh682PhB04+otBA8n/ad7lf/xo7CuE5qxM8aj43l9QZWqu r3rAZq7Qbbhy1ZWtvq9eHZ37zpCQlKdti88o85Hu3F40zsc8Ve oNMlWr8pQld+1nNRlzehUJonoKkWDJG/JRHJRlRyP+syFmvh1w IPbuGbNIAyrWi8weSXNBD5oJiRSeb/mNZCbfbsU9z/NgM9M0E0 xZRypZbAp9MfpbAqJiXgY7KARwaf+bzi+IMxT/RPSYnJ7F+UgR C/C+wcjNuzmBylQtHFnYTEhXmpSewMsFIWMbhMFyDSGwYFvwaF cTVnrp8LNhxSVXkIRwNCSibNT2gUQO6d6rHhK3Kx1 Subject: Re: [Thumbgps-devel] [ntp:questions] Fwd: Long term SiRF data / NMEA Wandering X-BeenThere: thumbgps-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 17 Mar 2012 21:32:00 -0000 Cross posting to the thumbgps-devel list. Ron On 3/17/2012 3:45 PM, Charles Elliott wrote: > I program the BU-353 with regular C++. I have a copy of the "SiRF NMEA > Reference Manual" (P/N: 1050-0042, Rev 2.2, 11/08) that I received from > > SiRF Technology, Inc. > 217 Devcon Drive > San Jose, CA 95112 > PH: +1(408) 467-0410 > support@SiRF.com. > > It contains descriptions of all the NMEA messages SiRF supports (both input > and output) and many of the SiRF proprietary messages. > > If SiRF is not forthcoming with another copy, I could try scanning it and > posting it on Windows Live. It is fairly long, so please let me know if you > need it. > > Charles Elliott > > >> -----Original Message----- >> From: questions-bounces+elliott.ch=verizon.net@lists.ntp.org >> [mailto:questions-bounces+elliott.ch=verizon.net@lists.ntp.org] On >> Behalf Of Ron Frazier (NTP) >> Sent: Saturday, March 17, 2012 2:49 PM >> To: questions@lists.ntp.org >> Subject: [ntp:questions] Fwd: Long term SiRF data / NMEA Wandering >> >> Hi all, >> >> This is a cross post from the [Thumbgps-devel] list. It relates to >> some testing on some SIRF GPS's the original poster is doing (at the >> bottom). >> The part on top is my reply to him. I thought those here might like >> to see it, considering recent GPS related discussions we've been >> having. >> >> Sincerely, >> >> Ron >> >> ----------------- >> >> Hi all, >> >> I've been seeing similar wandering of the NMEA output on my BU-353. >> This graph shows what looks like the internet servers (colored lines) >> wandering off while my pc is locked to gps time (dark jaggy baseline). >> I suppose it's actually the GPS wandering off. >> >> http://dl.dropbox.com/u/9879631/drifting01-peerstats.20120312.jpg >> >> Can someone please tell me, if known, why this happens? I've been >> discussing this a good bit on the NTP questions list. On my particular >> home network / internet connection, my offsets to internet servers with >> NTP running run about + / - 50 ms. I've decided to use the BU-353 GPS >> anyway, since in the short term, my offsets are + / - 6 ms or so, even >> if over days, my time varies + / - 70 ms from UTC. At least the >> variations are not every 15 minutes like they would be if I was polling >> the internet. I hope to shortly have a Sure Electronics GPS board and >> will be testing that. David Taylor, on the NTP questions list says the >> same NMEA wandering has been observed on the Garmin 18 ??. I'm not >> sure which model that was. >> >> Here's how to reprogram th BU-353. Lots of the support stuff is here: >> >> http://www.usglobalsat.com/s-122-bu-353-support.aspx >> >> However, the program we need is not. To program the unit, you need >> SirfDemo. >> >> First check out the FAQ here: >> >> http://www.usglobalsat.com/store/gpsfacts/bu353_gps_facts.html >> >> And you can find a link to SirfDemo here: >> >> http://www.usglobalsat.com/downloads/setupSiRFDemoV387.zip >> >> Unzip and install SirfDemo. Do the following to reprogram the BU-353. >> I assume other SirfIII units are similar. SirfDemo gives you access to >> a HUGE number of internal GPS functions, probably enough to really >> screw up the device if you're not careful. You can also do factory >> restarts, etc., from the menus. >> >> a) Shut down NTP, GPSD, or any other thing attached to the GPS virtual >> com port. >> b) Start SirfDemo. >> c) A Data Source window will pop up. Select the com port and data rate >> that the GPS is currently set to. If the baud rate is unknown, try >> 4800 then try to connect, then 9600, etc. If the com port is unknown, >> look in the Windows control panel, system, device manager under ports >> com and lpt to determine which com port is active. >> d) Under the view menu, turn on the Signal, Radar, Map, Messages >> Response, Messages Error, and Messages Debug windows if not on already. >> e) Click the 5th toolbar button, which is connect to data source. >> f) If the unit is outputting NMEA data, that should appear in the debug >> window. If it is outputting satellite data, you'll get that in the >> signal and radar windows. >> g) Under the Action menu, select switch to SIRF protocol. The NMEA >> data will stop and the response window will start outputting data. >> h) Under the Action menu, select switch to NMEA protocol. >> i) A parameter selection window will pop up. This allows the sentence >> output to be customized. Using the drop down boxes, put a 1 in every >> sentence you want to occur once per second. Put a 2 for once every 2 >> seconds, etc. Put a 0 if you don't want the sentence to appear at all. >> You can click in the first number field, type a number, and tab to >> the rest if you like. I leave checksums turned on. Select your baud >> rate, then click send. >> j) The response view windows should stop updating and the debug view >> should start up again with NMEA sentences. >> k) Click the 5th toolbar button again which will disconnect you from >> the GPS. >> l) Close SirfDemo. >> m) You are now ready to resume using the GPS with NTP as normal. >> >> There are many many other options you can choose from the menu options >> of SirfDemo, including a factory reset, should you need it. >> >> Hope this helps. >> >> Sincerely, >> >> Ron >> >> >> >>> I can't remember if I had shared this already. >>> >>> >>> ---------- Forwarded message ---------- >>> From: Hal Murray >>> Date: Tue, Oct 25, 2011 at 2:58 AM >>> Subject: Long term SiRF data >>> To: Eric Raymond >>> Cc: Hal Murray, Dave Taht >>> , Jim Getty, Gary Miller >>> >>> >>> >>> >>> I've been collecting data from 2 SiRF units. I'm up to about 12 days >>> >> now. >> >>> Quick summary: both suck. >>> >>> Both are located inside my house, poor conditions. >>> >>> >>> The first is a Holux GR-213. It's setup to only send GPRMC >>> >> sentences. >> >>> That's what I would use with ntpd. >>> >>> Here is the startup: >>> http://www.megapathdsl.net/~hmurray/bb/gps/Holux-1.png >>> >>> The green marks are "good" sentences. The Y offset is the difference >>> between the actual arrival time and the time stamp in the sentence. >>> The blue marks are the fraction part of the time stamp in the >>> sentence. The red marks are invalid sentences. >>> >>> At about -2.94 (hours) the reported time jumped by 1 second. My >>> >> guess >> >>> is that it learned about the latest leap second or something like >>> >> that. >> >>> At about -2.82 hours, the fractional part of the report switched to >>> >> 0. >> >>> I have no idea what caused that. It doesn't really matter much. It >>> wasn't useful anyway. >>> >>> Here is the big picture: >>> http://www.megapathdsl.net/~hmurray/bb/gps/Holux-2.png >>> There is a mode shift every 1-3 days. What's the right term? >>> >>> For reference, here is an old graph with the mode shift every 8-12 >>> >> hours. >> >>> http://www.megapathdsl.net/~hmurray/bb/gps/SiRF-GPRMC-4800.png >>> >>> This is the previous 2 pictures glued together: >>> http://www.megapathdsl.net/~hmurray/bb/gps/Holux-3.png >>> >>> Here is one day: >>> http://www.megapathdsl.net/~hmurray/bb/gps/Holux-4.png >>> >>> ------------- >>> >>> The second unit is a Global Sat BU-353. It ignored my attempts to >>> change the configuration, so I let it run in the default setup. >>> Normally it sends GPGGA, GPGSA, and GPRMC. Every 5 seconds it >>> includes 3 GPGSV sentences before the GPRMC. I think that fits in 1 >>> second at 4800 baud, but the GPRMC gets pushed over to the next >>> >> second. >> >>> Here is the graph for the GPGGA sentences: >>> http://www.megapathdsl.net/~hmurray/bb/gps/BU-353-gpgga.png >>> The long term cycle time is 8-10 days. >>> >>> Here is the graph for the GPRMC sentences: >>> http://www.megapathdsl.net/~hmurray/bb/gps/BU-353-gprmc.png >>> The top band of green is the data that gets pushed over to the next >>> >> second. >> >>> The blue and purple are the number of satellites. (They are scaled >>> >> up >> >>> by >>> 100.) I don't see any pattern. >>> >>> This unit doesn't always return 000 for the fraction part of the time >>> >> stamp. >> >>> Sometimes it's 998 or 999 with the previous second. >>> http://www.megapathdsl.net/~hmurray/bb/gps/BU-353-gpgga-off.png >>> >>> >>> >>> -- >>> These are my opinions, not necessarily my employer's. I hate spam. >>> >>> >>> questions mailing list >>> questions@lists.ntp.org >>> http://lists.ntp.org/listinfo/questions >>> -- (PS - If you email me and don't get a quick response, don't be concerned. I get about 300 emails per day from alternate energy mailing lists and such. I don't always see new messages very quickly. If you need a reply and have not heard from me in 1 - 2 weeks, send your message again.) Ron Frazier timekeepingdude AT c3energy.com