[time-nuts] BC637PCI 1024 week rollover

d0ct0r time at patoka.org
Sun Feb 9 09:55:48 EST 2014


Hello,

I'll be glad to check my GPS module to see what is going on there, 
however I am still waiting for the GPS antenna to be delivered. I tried 
to use some small form factor Trimple GPS antenna with BC637, but 
on-board GPS module couldn't lock with it. So, my BC637 is working in 
"freerun" mode now:

Time Settings:

  Mode                           : Free Run
  Time Format                    : Binary
  Year                           : 2014
  Local Offset                   : 0.0
  Propagation Delay              : 0
  Current Leap Seconds           : 0
  Scheduled Leap Event Time      : 1391731200
  Scheduled Leap Event Flag      : Insertion
  GPS Time Format                : UTC Format
  IEEE Daylight Savings Flag     : Enable

I have no issues with date stamp in that mode:

Binary Time: 02/09/2014  14:36:19.7005289   Status: 0
Binary Time: 02/09/2014  14:36:19.7105941   Status: 0
Binary Time: 02/09/2014  14:36:19.7206589   Status: 0

Even if I switch BC637 to "GPS mode, it still using correct date. Which 
is expected, because in accordance with documents, if GPS is not locked, 
BC637 will behave in the same way as "free run". The difference is the 
Status. Its shows, four bits. And one of them indicates that GPS is not 
locked:

Binary Time: 02/09/2014  14:37:43.0045326   Status: 7
Binary Time: 02/09/2014  14:37:43.0146051   Status: 7
Binary Time: 02/09/2014  14:37:43.0246776   Status: 7


As soon as I'll get my "bullet GPS antena" attached, I'll see what is 
going on there for the date stamp. Also, in the documents, I saw some 
sections, which explain how to use data registers to send some command 
to Trimble GPS. Probably its is possible to do some corrections through 
that procedure.
May be it is possible to attach another GPS module to the BC637 card. 
Its using 9 pin connector.
This connector is used primarily for connecting the ACE III GPS. Data 
communications
between the board and the GPS receiver are via serial signals. 
Additionally, the GPS receiver
provides a 1 PPS signal to the board.


Regards,

V.P.



On 2014-02-09 06:56, GandalfG8 at aol.com wrote:
> Oh well, full credit to Mr Trimble for getting it right, he does bake
> exceedingly nice GPS modules and the Ace3 doesn't have a rollover issue 
>  and it
> does report the date correctly.
> 
> Unfortunately, as far as I can tell anyway, the BC637PCI takes the raw 
> GPS
> time data from the Ace3 and performs its own calculation which is where 
> the
>  problem seems to occur, certainly it's a 1024 week issue with the date
> from  the BC637 being displayed as June 26 1994 in all versions of the
> associated  demo software.
> It is possible to set the date correctly but the next packet from the 
> GPS
> module promptly overwrites it again.
> 
> I still don't recall seeing this before, although with two boards  
> behaving
> in the same fashion I'm having doubts about that, but more to the point
> these boards indicate a firmware date of 2003 which implies they were  
> put
> into the field like this, and that doesn't make much sense  either.
> 
> Any ideas anyone?, and again has anyone else seen this and/or am I 
> missing
> something glaringly obvious?
> 
> Regards
> 
> Nigel
> GM8PZR
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
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-- 
WBW,

V.P.


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