[time-nuts] BC637PCI 1024 week rollover
GandalfG8 at aol.com
GandalfG8 at aol.com
Tue Feb 11 12:09:28 EST 2014
Ah, sorry, when you commented before about modifying the demo software it
obviously didn't register with me quite what you were trying to do.
In the BC637PCI Demo software, I'm using version 7.0.0, under the "Help"
menu, one item is Receiver Firmware Version and this returns the Packet 45
If it's any consolation, mine is the same as yours, except for the date
showing as 4/1/1900:-)
2000 doesn't seem unreasonable for the Ace3 firmware date, my BC637
itself, another drop down on that same Help menu, shows as Version DT10041V12,
Number 2.21, Date 2/10/2003, which ties in pretty well with Symmetricom
completing their takeover of Datum in late 2002 and introducing their BC637PCI-U
own brand replacement in 2004.
What I do find intriguing though is that your Packet 41 data is returning
the correct GPS week number and Leap Second offset when there's no antenna
connected, how the heck does it do that?:-)
In a message dated 11/02/2014 16:36:21 GMT Standard Time, time at patoka.org
I figured out why GPS FW information was not available by request. To do
such requests BC637PCI needs to be in "GPS MODE". If I run the request
in "Free Run", it return the error code. Here is FW infomation from my
GPS Packet Menu
1. Request Packet 41 - Gps Time Packet
2. Request Packet 42 - Gps Position Packet
3. Request Packet 46 - Gps Health Packet
4. Request Packet 45 - Gps FW
0. Back to main menu
GPS PACKET 41 - GPS TIME PACKET
Seconds of Week: 232505.89
GPS Week Number: 1779
GPS/UCT Offset: 16.00
GPS PACKET 45 - GPS FW
FW: 08-08, 04/01/2000 : 10-16, 04/01/2000
If its correct, than I have pretty old GPS module. I got my GPS antenna,
however it has N-type connector on it. Now I need to find the way to
connect it to SMA.
On 2014-02-10 18:51, GandalfG8 at aol.com wrote:
> In a message dated 10/02/2014 21:56:25 GMT Standard Time,
> magnus at rubidium.dyndns.org writes:
> On 10/02/14 11:15, GandalfG8 at aol.com wrote:
>> Ah, I took 1999 as I thought that was the only relevant date for
>> 1024 weeks, I'm not familiar with the shifted 1024 week period so
> take a
>> look at that.
>> Does "shifted" imply a shift at the whim of the manufacturer, ie
>> explain why these boards might have been ok a few years ago but not
> Yes. We have seen week 500 and week 512 occuring.
> Considering this simple code:
> if (gpsweek < 500)
> gpsweek += 1024;
> This means that GPS week 500 to 1023 maps straight and truncated GPS
> week 0 to 499 is mapped to GPS week 1024 to 1523.
> However, when GPS week 1524 occurs, GPS week 500 is transmitted, so
> receivers jump from GPS week 1523 to GPS week 500 and the NMEA readout
> date jumps 19.3 years. Woops.
> The interesting thing is that the GPS otherwise operate properly, as
> is only the read-out date which goes wrong, not the internal gears of
> the GPS, so the leap second applied will be the current and not the
> from 19 years ago.
> Yes, that's what I was seeing, anything received by the GPS module was
> passed through correctly, week number, leap seconds, etc, it was what
> the BC637
> did with it after that wasn't quite so helpful.
>> Oh dear, I think a wee light bulb has just exploded:-)
> Good. :)
>> I haven't checked this yet, but if shifting means to start a 1024
>> period that's approximately from or not too far before the date of
>> manufacture, either for individual units or just as a ballpark for a
> given production
>> run, that would buy them nearly twenty years from then, which would
>> these boards should still be ok.
> It's arbitrary. It could be from writing the code to just before a
> certain batch. Who knows. Adjusting it is trivial.
>> If shifting means to do this say at the design stage or starting with
>> first production run then they might buy twenty years from then but
>> regardless of individual manufacturing date.
> It's arbitrary. Considering that GPS week 500 and GPS week 512 have
> found in equipment, and these are not "random numbers", it seems like
> random pick early in the design.
>> I'm not too sure that even the earliest of these boards should be
>> years old yet, but if plan Z was to stick with some previously picked
>> arbitrary date, such as company formation or granny's birthday, then
> that might
>> well be the answer:-)
>> Thank you, will definitely look more closely at this, perhaps it's
>> yet to put the boards back into hibernation after all:-)
> Good, now you learned something. :)
> Certainly seems that way, perhaps the old brain cell does still fire
> now and again after all:-)
> I was quite surprised though just how little a Google search threw up
> 1024 week offsets, however I worded it I got plenty of hits regarding
> 1024 week rollover itself, plus its implications, but virtually
> regarding the use of offsets and any consequences of that.
>> I agree re the TMS29F010, and I'm sure I could read it, but would
>> definitely need an adapter for that.
> Ah. Yes.
> I don't know what FW my boards have, if it has the GPS FW latent or
> I bought a set of PLCC adapters on Ebay this afternoon, probably about
> my programmers joined the 19th century, so with a bit of luck, a
> wind, and a good head of steam, I might even have a dump of the
> by the weekend:-)
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