marks@non-stop.com.au said:

Is that off by 1024 weeks?  (Looks close, but I haven't checked the details.)

There is a week field in the GPS data stream.  It's only 10 bits.

I had that problem on a Z3801A.  It did the right thing after I told it the
date.
:GPS:INIT:DATE 2011,12,26

--
These are my opinions.  I hate spam.

Hal, I can't get it to take, I keep getting E-350 and the time does not change.
Did you unplug the antenna or anything while you changed date?

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Hal Murray
Sent: Sunday, 11 August 2013 12:54 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

marks@non-stop.com.au said:

Is that off by 1024 weeks?  (Looks close, but I haven't checked the details.)

There is a week field in the GPS data stream.  It's only 10 bits.

I had that problem on a Z3801A.  It did the right thing after I told it the date.
:GPS:INIT:DATE 2011,12,26

--
These are my opinions.  I hate spam.

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.

I just checked by Z3801A which is being monitored by SatStat on an old
laptop. Mine is showing the correct date and time.

Joe Gray
W5JG

On Sat, Aug 10, 2013 at 8:53 PM, Hal Murray hmurray@megapathdsl.net wrote:

Okay this is what worked for me:

1. Removed power and antenna.
2. apply power with no antenna.
3. send :GPS:INIT:DATE 2007,08,11
4. plug antenna back in.

For some reason if I used the correct date, the Z3815A warped back to 1993.

But I am curious why did this happen today?

--marki

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Mark C. Stephens
Sent: Sunday, 11 August 2013 1:06 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

Hal, I can't get it to take, I keep getting E-350 and the time does not change.
Did you unplug the antenna or anything while you changed date?

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Hal Murray
Sent: Sunday, 11 August 2013 12:54 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

marks@non-stop.com.au said:

Is that off by 1024 weeks?  (Looks close, but I haven't checked the details.)

There is a week field in the GPS data stream.  It's only 10 bits.

I had that problem on a Z3801A.  It did the right thing after I told it the date.
:GPS:INIT:DATE 2011,12,26

--
These are my opinions.  I hate spam.

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
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and follow the instructions there.

I have 5 Z3805A and only one had the wrong date.
They all have identical GPS modules and firmware so I don't know why just one decided to warp back to 1993.

The Z3815A is still stuck at 1993, I can't even set it to 11 Aug 2007. (-1024) even with antenna unplugged and power cycle.
I mean, Can set it to 11 Aug 2007, but after the 1st bird it sees it goes back to 1993.

I might try a factory default and see how we go.

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Joseph Gray
Sent: Sunday, 11 August 2013 1:16 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

I just checked by Z3801A which is being monitored by SatStat on an old laptop. Mine is showing the correct date and time.

Joe Gray
W5JG

On Sat, Aug 10, 2013 at 8:53 PM, Hal Murray hmurray@megapathdsl.net wrote:

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.

Nope, I tried all the resets I could find, I can set the date right but as soon as the Z3815A sees a bird, it jumps back to 1993.
How annoying, Anyone else with a Z3815A having problems?

--marki

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Mark C. Stephens
Sent: Sunday, 11 August 2013 2:40 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

I have 5 Z3805A and only one had the wrong date.
They all have identical GPS modules and firmware so I don't know why just one decided to warp back to 1993.

The Z3815A is still stuck at 1993, I can't even set it to 11 Aug 2007. (-1024) even with antenna unplugged and power cycle.
I mean, Can set it to 11 Aug 2007, but after the 1st bird it sees it goes back to 1993.

I might try a factory default and see how we go.

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Joseph Gray
Sent: Sunday, 11 August 2013 1:16 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

I just checked by Z3801A which is being monitored by SatStat on an old laptop. Mine is showing the correct date and time.

Joe Gray
W5JG

On Sat, Aug 10, 2013 at 8:53 PM, Hal Murray hmurray@megapathdsl.net wrote:

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.

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and follow the instructions there.

Today is start of new epoch.

As per:
http://adn.agi.com/GNSSWeb/

1753:0  Full GPS week since 1st epoch : day of week number
729:0 GPS Week since latest epoch : seconds of week at midnight for that day

So that explains what happened.

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Mark C. Stephens
Sent: Sunday, 11 August 2013 1:19 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

Okay this is what worked for me:

1. Removed power and antenna.
2. apply power with no antenna.
3. send :GPS:INIT:DATE 2007,08,11
4. plug antenna back in.

For some reason if I used the correct date, the Z3815A warped back to 1993.

But I am curious why did this happen today?

--marki

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Mark C. Stephens
Sent: Sunday, 11 August 2013 1:06 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

Hal, I can't get it to take, I keep getting E-350 and the time does not change.
Did you unplug the antenna or anything while you changed date?

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Hal Murray
Sent: Sunday, 11 August 2013 12:54 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

marks@non-stop.com.au said:

Is that off by 1024 weeks?  (Looks close, but I haven't checked the details.)

There is a week field in the GPS data stream.  It's only 10 bits.

I had that problem on a Z3801A.  It did the right thing after I told it the date.
:GPS:INIT:DATE 2011,12,26

--
These are my opinions.  I hate spam.

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.

On 08/11/2013 05:18 AM, Mark C. Stephens wrote:

GPS weeks begin on sundays. Today is first day of week 1753:

http://csrc.ucsd.edu/scripts/convertDate.cgi?time=2013+08+11

Going back 1024 days gives you week 729 day 0, which occurs on 1993 12 26:
http://csrc.ucsd.edu/scripts/convertDate.cgi?time=1993+12+26

A simple way to compensate for the lack of bits is to assume wrapping
occurs, so week numbers lower than som value actually lacks 1024 weeks.
A trivial code like this fixes this:

if (week < 729)
week += 1024;

Brilliant until you reach week 1753.

I've seen this happen at 500 and 512.

Cheers,
Magnus

OK, good, found the bug. Now, iwe wish it were possible to download
the firmware, make the correction and then upload...

On Sun, Aug 11, 2013 at 1:14 PM, Magnus Danielson
magnus@rubidium.dyndns.org wrote:

Azelio, is your Furuno playing up?

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Azelio Boriani
Sent: Sunday, 11 August 2013 9:30 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

OK, good, found the bug. Now, iwe wish it were possible to download the firmware, make the correction and then upload...

On Sun, Aug 11, 2013 at 1:14 PM, Magnus Danielson magnus@rubidium.dyndns.org wrote:

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.

Hi

One point worth mentioning - the device will still be quite happy acting as a GPSDO. It simply will not be of much use for NTP (or any other date dependent system).

Bob

On Aug 11, 2013, at 7:44 AM, Mark C. Stephens marks@non-stop.com.au wrote:

If Furuno can supply the FW to update with, we would be more than happy.

A slight alteration of the code would suffice...

if (week < 729)
week += 2048;
else
week += 1024;

Which would keep them floating for another 1024 weeks. If they then let
us know where the two constats is located so we could modify it again
ourselves we be very happy.

Cheers,
Magnus

On 08/11/2013 01:29 PM, Azelio Boriani wrote:

On 08/11/2013 03:08 PM, Bob Camp wrote:

I'm sure that the NTP drivers can be hacked to make necessary
adjustments without too much code.

It is after all very likely that a GPS clock has wrapped a multiple of
1024 weeks.

Cheers,
Magnus

Hi

… and since NTP is open source, doing the hack is not dependent on getting a new firmware image for the GPS.

Bob

On Aug 11, 2013, at 9:12 AM, Magnus Danielson magnus@rubidium.dyndns.org wrote:

Hi Bob,

On 08/11/2013 03:37 PM, Bob Camp wrote:

Yes, but it only helps the NTP side of things.

Made a point about the wrap-around-compensation on one of the NTP lists
just now, they happen to get things a bit confused for a moment.

Still, it would be good if they could keep FW updates available.
Naturally, if they could drop the sources my way I would enjoy that even
more.

Cheers,
Magnus

Furuno will not give you the time of day :-) :-)
Don

Magnus Danielson

--
“The power of accurate observation is commonly called cynicism by those
who have not got it.”
-George Bernard Shaw

Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com

Bob Camp wrote:

Hacking ntpd is one possibility, with the risk that a workaround for
some broken GPS receiver also affects GPS receivers which are working
correctly.

At least in some of ntpd's refclock drivers you can configure a fixed
offset using a "fudge time1 ..." command., e.g. for the parse driver

fudge 127.127.8.0 time1 7200

would add a 7200 s offset to the time from the refclock. As far as I
know this also works for larger offsets, at least with the parse driver,
and this possibly can also be used to fix a constant offset for broken
GPS receivers, depending of the refclock driver used.

Anyway, I think it's worth a try, and it would not require any code
change in ntpd or the firmware.

Martin

Hi

Well, if it works fine as a GPSDO, and NTP can be fixed to work with it, that covers ninety something percent of what most people do with this sort of stuff.

Bob

On Aug 11, 2013, at 9:43 AM, Magnus Danielson magnus@rubidium.dyndns.org wrote:

Hi

I think that without much risk, you could put in a "gps epoch" setting in the ntp configuration file. More or less make it a "check and correct if needed" sort of thing. No setting in the file would mean disable the check and correct code.

Bob

On Aug 11, 2013, at 12:58 PM, Martin Burnicki martin.burnicki@burnicki.net wrote:

On Sun, Aug 11, 2013 at 03:12:00PM +0200, Magnus Danielson wrote:

I seem to have been caught by the same time warp (or a similar one)
on a GPS unit that I've been using with our NTP server since 1999.
I doubt I will be able to update the firmware, so I've made the
change shown below to the NTP NMEA refclock. It assumes that your
GPS unit might be slow by a multiple of 1024 weeks, and trys to get
the timestamp within 512 weeks of the current system time before
feeding it to NTP.

The patch seems to work for me, though it may not be pedantically
correct. Hal might have some comments on if it could easily be
improved. It might be an interesting option to have in the NMEA
driver, but it does seem a litle hacky.

David.

--- refclock_nmea.c.orig 2010-11-10 03:38:22.000000000 +0000
+++ refclock_nmea.c 2013-08-13 20:05:44.000000000 +0100
@@ -979,6 +1076,8 @@
date.yearday = 0; /* make sure it's not used */
DTOLFP(pp->nsec * 1.0e-9, &reftime);
reftime.l_ui += caltontp(&date);

• while (reftime.l_i + 512786400 < rd_timestamp.l_i)

•   reftime.l_i += 1024*7*86400;
  

  /* $GPZDG postprocessing first... */
  if (NMEA_GPZDG == sentence) {