Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver
> Tom, > > In my TB monitor kit, I used your Julian date routines, adapted to the 8051 > (no variable greater than 32 bits since my compiler does not support them > either) to apply the GPS offset correction. It was very helpful. > > Didier KO4BB Right. There are many ways to address the 1024 week rollover. Mark uses JD and floating point because his program contains lots of astronomical features and JD is useful and popular in that context. I suspect the code you're using is from this demo -- http://leapsecond.com/tools/tbolt1.c -- which is based on MJD and integer only. The code I mentioned today -- http://leapsecond.com/tools/gpsdn.c -- is similar except its based on GPSDN instead of MJD. I came up with GPSDN because it's easier to work with GPS cycles when the origin of GPS time is GPSDN = 0 instead of something like MJD = 44244, or JD = 2444244.5, or unix_time_t = 315964800, or Excel date 29226. If you display GPSDN as hex or binary, GPS rollovers are a picture-worthy ripple-carry binary odometers: 1999-08-21 = GPSDN 7167 = 0x1BFF = 0b11011 1999-08-22 = GPSDN 7168 = 0x1C00 = 0b11100 2019-04-06 = GPSDN 14335 = 0x37FF = 0b110111 2019-04-07 = GPSDN 14336 = 0x3800 = 0b111000 2038-11-20 = GPSDN 21503 = 0x53FF = 0b1010011 2038-11-21 = GPSDN 21504 = 0x5400 = 0b1010100 2058-07-06 = GPSDN 28671 = 0x6FFF = 0b110 2058-07-07 = GPSDN 28672 = 0x7000 = 0b111 While I'm at it, and for newcomers to the group, note that GPS rollovers occur about every 19.6 years (1024 weeks) and occur in "GPS time", which is offset from "UTC time" by a particular number of leap seconds. That's why GPS rollovers do not occur at precisely midnight on the dates listed above. Also why it's not possible to list the exact time of future GPS rollovers as UTC date & time. Hint: stay well away from self-driving vehicles during leap seconds and GPS rollovers. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Setting correct date on Trimble Thunderbolt receiver
Thanks, excellent code to do the fixup on Arduinos, etc. Heather already has Julian <-> Gregorian routines that use double precision numbers and allows date/time tweaks to millisecond levels, so I used those. I am modifying the rollover adjustment code to not latch onto a specific rollover compensation value. That was originally done for a couple of old receivers that did things rather bizarrely. Subsequent improvements to the code made that no longer necessary. So now Heather will be able to recover from date/time issues due to bogus dates that occur during receiver startup. > Ah, more complicated math to solve a problem vs. simpler math to avoid a > problem in the first place. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver
Tom, In my TB monitor kit, I used your Julian date routines, adapted to the 8051 (no variable greater than 32 bits since my compiler does not support them either) to apply the GPS offset correction. It was very helpful. Didier KO4BB On Wed, Mar 28, 2018, 7:13 AM Tom Van Baak wrote: > Hi Mark, > > > Heather keeps all times as a double precision Julian date. Using > Heather's code can > > be a problem on Arduinos since their "double" precision numbers are > actually 32 bit > > single precision, so you would need to do some more complicated math. > > Ah, more complicated math to solve a problem vs. simpler math to avoid a > problem in the first place. > > Here's a simple "GPS Day Number" example: www.leapsecond.com/tools/gpsdn.c > > To add 1024 weeks to a given date use: > > gpsdn = date_to_gpsdn(year, month, day); > gpsdn += 1024 * 7; > gpsdn_to_ymd(gpsdn, &year, &month, &day); > > That's it. It uses 32 bit integers; no floating point required; works on > any OS, or Arduino. > > /tvb > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver
Hi > On Mar 28, 2018, at 12:10 AM, Mark Sims wrote: > > Lady Heather's automatic rollover fixer works by looking at the year in any > time message that it sees. If it sees 10 consecutive year values less than > 2016, it assumes the receiver has rollover issues and then adds 1024 weeks > worth of seconds to the Julian date/time calculated from the receiver > time/date message until the resulting year is past 2016. > > One problem with this is when a receiver is first powered up... most of them > send dates in the 1980s to 1990s until they start tracking satellites. Once > Heather detects a rollover condition, the code does not currently undo it if > the receiver starts sending good dates. > > Heather keeps all times as a double precision Julian date. Using Heather's > code can be a problem on Arduinos since their "double" precision numbers are > actually 32 bit single precision, so you would need to do some more > complicated math. > > Heather's rollover compensation value is actually in double precision > seconds. You can manually specify a rollover correction to sub-second > resolution and tweak the displayed time/date to anything you want... comes > in handy for testing calendar/eclipse/sunrise/sunset/etc code. > > Speaking of rollovers, the GPS system has a 1024 week rollover next year > (April 6th-7th). A lot of older receivers had code that could handle the > first system rollover in 1999, but might have issues this time. There are a surprising number of GPS modules that really don’t handle the rollover very well. That includes a significant number of designs that came out after 1999. Bob > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver
Hi Mark, > Heather keeps all times as a double precision Julian date. Using Heather's > code can > be a problem on Arduinos since their "double" precision numbers are actually > 32 bit > single precision, so you would need to do some more complicated math. Ah, more complicated math to solve a problem vs. simpler math to avoid a problem in the first place. Here's a simple "GPS Day Number" example: www.leapsecond.com/tools/gpsdn.c To add 1024 weeks to a given date use: gpsdn = date_to_gpsdn(year, month, day); gpsdn += 1024 * 7; gpsdn_to_ymd(gpsdn, &year, &month, &day); That's it. It uses 32 bit integers; no floating point required; works on any OS, or Arduino. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Setting correct date on Trimble Thunderbolt receiver
Lady Heather's automatic rollover fixer works by looking at the year in any time message that it sees. If it sees 10 consecutive year values less than 2016, it assumes the receiver has rollover issues and then adds 1024 weeks worth of seconds to the Julian date/time calculated from the receiver time/date message until the resulting year is past 2016. One problem with this is when a receiver is first powered up... most of them send dates in the 1980s to 1990s until they start tracking satellites. Once Heather detects a rollover condition, the code does not currently undo it if the receiver starts sending good dates. Heather keeps all times as a double precision Julian date. Using Heather's code can be a problem on Arduinos since their "double" precision numbers are actually 32 bit single precision, so you would need to do some more complicated math. Heather's rollover compensation value is actually in double precision seconds. You can manually specify a rollover correction to sub-second resolution and tweak the displayed time/date to anything you want... comes in handy for testing calendar/eclipse/sunrise/sunset/etc code. Speaking of rollovers, the GPS system has a 1024 week rollover next year (April 6th-7th). A lot of older receivers had code that could handle the first system rollover in 1999, but might have issues this time. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver
In general, I believe whether you can work around the 1024 week problem and if so, how, tends to be a receiver-by-receiver thing (or at least manufacturer-by-manufacturer). I’m most familiar with the SkyTraq Venus838, and those have a sliding window system where you set a “reference date” and the receiver will always assume that date is inside the window. At least once every 1024 weeks, you’re supposed to set that to the current date (it’s a binary command and they have software that will do this for you), and then you’ll get another 1024 weeks without having to do anything. My GPSDOs don’t have a TX path from the controller to the receiver, but you can talk to the receiver directly with the diagnostic connector and update the reference date that way. My GPS Clocks will set the reference date once a year (if the current year != the reference date year, then it is set, and this check is made once an hour. Having the date correct matters for DST decisions). > On Mar 26, 2018, at 5:03 PM, David C. Partridge > wrote: > > AFAIK you can't set the correct date any more - this is the 1024 week > rollover problem. > > Lady Heather does correct the displayed date, as it knows that the reported > date is wrong.. > > David > > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of > donandarl...@gmail.com > Sent: 26 March 2018 22:18 > To: time-nuts@febo.com > Subject: [time-nuts] Setting correct date on Trimble Thunderbolt receiver > > Hello all, > I am new to the board and have just received a Trimble Thunderbolt GPS > receiver today. > All is working correctly except the date shows Aug 10 1998. > How do set the proper date on this? > I am running TBoltMon to access the unit. > Any help would be appreciated. > Thanks, > Don W9BHI > ___ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver
On Mon, March 26, 2018 6:49 pm, Tom Van Baak wrote: > The bad news is that if you use the Trimble TSIP RS232 interface and if > you want the correct date & time then the software needs to be aware of > the 1024 week (19.6 year) epoch. This "GPS 1024 week rollover" issue Many people do not use the date directly, it is served to other machines via other software such as ntpd. You should be able to configure ntpd to add an appropriate offset such that the correct date is served. If using directly (e.g. a machine is logging data and communicating directly with the Tbolt to get date stamps) you would have to add the equivalent offset yourself. -- Chris Caudle ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver
AFAIK you can't set the correct date any more - this is the 1024 week rollover problem. Lady Heather does correct the displayed date, as it knows that the reported date is wrong.. David -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of donandarl...@gmail.com Sent: 26 March 2018 22:18 To: time-nuts@febo.com Subject: [time-nuts] Setting correct date on Trimble Thunderbolt receiver Hello all, I am new to the board and have just received a Trimble Thunderbolt GPS receiver today. All is working correctly except the date shows Aug 10 1998. How do set the proper date on this? I am running TBoltMon to access the unit. Any help would be appreciated. Thanks, Don W9BHI ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver
Don, The primary purpose of a Thunderbolt GPSDO is ultra-precise time (1PPS) and frequency (10 MHz), locked to each other, and to UTC. The good news is these two BNC outputs are unaffected by the date issue that you describe. The TBolt is designed to run fine on its own; you typically don't need a PC or control program to operate it. The bad news is that if you use the Trimble TSIP RS232 interface and if you want the correct date & time then the software needs to be aware of the 1024 week (19.6 year) epoch. This "GPS 1024 week rollover" issue eventually affects many receivers, including the TBolt, but the good news is that simple work-arounds are often available to address the problem. AFAIK, the Tboltmon.exe program has *not* been updated. I still use it (when you're dealing with nanoseconds, calendar dates are less important). Mark's LH program *has* been updated. See: http://www.ke5fx.com/heather/readme.htm Didier's LCD date/time display *has* been updated: http://www.ko4bb.com/Timing/GPSMonitor/kit.php /tvb - Original Message - From: To: Sent: Monday, March 26, 2018 2:17 PM Subject: [time-nuts] Setting correct date on Trimble Thunderbolt receiver > Hello all, > I am new to the board and have just received a Trimble Thunderbolt GPS > receiver today. > All is working correctly except the date shows Aug 10 1998. > How do set the proper date on this? > I am running TBoltMon to access the unit. > Any help would be appreciated. > Thanks, > Don W9BHI > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Setting correct date on Trimble Thunderbolt receiver
Hello all, I am new to the board and have just received a Trimble Thunderbolt GPS receiver today. All is working correctly except the date shows Aug 10 1998. How do set the proper date on this? I am running TBoltMon to access the unit. Any help would be appreciated. Thanks, Don W9BHI ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
