[time-nuts] BC637PCI and OCXO

GandalfG8 at aol.com GandalfG8 at aol.com
Fri Feb 7 13:28:55 EST 2014


 
The information you need is more in the description of the software  
commands, this will tell you how to switch between the internal and  external 
oscillators and how to vary the conditioning parameters and I'm pretty  sure, 
although it's been a while so might be wrong, that some of the software  
contains menus to make this more straightforward.
 
As long as what you have has already been configured as a BC637, ie  
existing firmware is aware that the GPS module is fitted, then there's no  further 
change required to attach an external oscillator, as per above all  the 
commands to do this are already available.
 
In manual version K see page 6-4 and 6-15 for info on command 0x25, set  
disciplining gain.
See page 3-6 section 3-5 on Hardware Menu option in the software....
 
keep on reading the manuals:-)
 
Regards
 
Nigel
GM8PZR

 
 
In a message dated 07/02/2014 18:06:55 GMT Standard Time, time at patoka.org  
writes:



Thanks everybody for the bit of information !

I have  a "Revsion C" and "Revision K" manuals. In Revison "K" its only 
one note  about OCXO:

"An internal 10 MHz VCXO (Voltage Controlled Crystal  Oscillator) is 
disciplined to the
reference source. The VCXO output  drives all timing functions on the 
card. The VCXO
output and a 1pps  signal are provided as outputs. The TFP is also 
capable of disciplining  an
external voltage controlled oscillator. As an option, the TFP board can  
be ordered with an
OCXO (Oven Controlled Crystal Oscillator)  installed."

As far as I understood, if I'll implement external OCXO to  my BC637, 
I'll need to change FW on the card to make it work. If so, its  not an 
option for me, since I just bought that card from auction and there  is 
no way to obtain new microcode for it.

Off-topic:

Aside  of that OCXO implementation, I would like to ask some direction 
from  time-nuts community about the relatively simple way to compare two 
1PPS  signals using some MCU. Lets say I have T-Bolt and BC637. Each has 
1PPS  and I would like to see the phase difference between of that two. 
Of  course it is some instruments already available for that, but I have 
not  own that one (yet). I am thinking to connect both 1PPS to Timers 
input in  "capture" mode on MCU. Then register first raising edge, start 
counting of  ticks until second timer will not catch another signal 
raise. Then number  of ticks will indicate the difference. But may be it 
is more "elegant" way  to do that comparison ? Thanks !

Regards,

V.P.



On  2014-02-07 03:38, GandalfG8 at aol.com wrote:
> I played with this around  five or six years ago but unfortunately  my 
> notes
> from  that time are likely to be buried somewhere still  waiting to be
>  scanned or indexed.
> 
> All the necessary information though is  in the user and SDK manuals,
> connections for the 10MHz external input  and EFC output are on the 15 
> way I/O
> connector and there's  even demo software which I'm pretty sure was all 
> I  used
>  to make the necessary adjustments.
> One manual, pre Symmetricom, even  has what looks to be a full set of
> schematics.
> 
> I've  just run the software again to check but it won't do much if  it 
>  can't
> find the card so would need to fire up another PC with a  spare  slot to
> check further.
> 
> I wasn't really  happy at the time with my attempts to  condition an
> external  Vectron OCXO, it was certainly better than using the
> internal  oscillator
> but there were some odd jumps and drifts using either  which  suggested 
> these
> might be artifacts of the board  itself rather than the  Vectron OCXO.
> 
> I've since  acquired another BC637PCI, and want to try both again with
> other  oscillators, but that's quite some way down a very  long to do 
>  list, now
> reminded though I might take a quick  look  later:-)
> 
> In the meantime, I have got copies of manuals and  software  etc and 
> will
> get those zipped up today and  make them available  for download.
> 
> Regards
>  
> Nigel
> GM8PZR
> 
> 
> 
> 
>  
> 
> 
> 
> 
> In a message dated 07/02/2014  03:36:46 GMT Standard Time, 
> time at patoka.org
> writes:
>  
> 
> Hello,
> 
> Does anybody seen any links to the  information  how to implement 
> external
> OCXO to  Symmetricom PCI TFP BC635/BC637  ?
> 
> 
> --
>  WBW,
> 
> V.P.
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--  
WBW,

V.P.
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