[time-nuts] BC637PCI 1024 week rollover

GandalfG8 at aol.com GandalfG8 at aol.com
Sun Feb 9 16:05:59 EST 2014


In a message dated 09/02/2014 15:31:47 GMT Standard Time,  
magnus at rubidium.dyndns.org writes:

On  09/02/14 12:56, 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?

If the ACE3 gives correct date, but the  BC637 FW does not, then it is 
obvious that the FW does the unwrapping  itself just like a problematic 
GPS receiver would. Most probably would the  ACE3 have issues if it 
looses it's CMOS backup.

I haven't looked at  those details, but you should be able to disable the 
date from being set  by the GPS. Maybe play around there.

Might be that the FW needs an  update, which naturally may not be in 
existence. Can you read-out the  EPROM?

Only proves to show that my comment that NTPD needs to do the  1024 week 
correction for other GPS dependent drivers than the NMEA (NTP  bug 2466) 
is a correct assumption. See the posting I forwarded  yesterday.

Cheers,
Magnus
Hi Magnus, and thanks for your comments.
 
I arrived at the same conclusion regarding the BC637 firmware and  that's 
the issue I'd like to resolve, but I'm a bit cautious given that these  were 
produced after 1999 as I can't understand why the firmware wouldn't already  
have been updated.
 
It is possible to set the board for other than GPS, (Timecode, Freerunning, 
 or 1PPS) but I suspect I might then loose the conditioning, something I'd  
need to check. Either way, I'd like to have the correct GPS date too if  
possible, but it's the conditioning that's of more interest so I'd do without  
the correct date if needs be.
 
I've identified two programmable devices, the version H manual  with 
schematics is very useful:-), the first being a OTP configuration PROM  for the 
Spartan FPGA and the other a TMS29F010 flash mamory IC which I suspect  holds 
the firmware. That is socketed but I don't think I have the necessary 32  
pin quad adapter to be able to read it.
 
This was only intended to be a quick test, funny how "quick  tests" soon 
become major projects:-), so these might have to go back  into hibernation 
again shortly, for the time being at least.
 
Regards
 
Nigel
 
 
 


More information about the time-nuts mailing list