[time-nuts] Why using HP5370 ext-ref is (maybe) a bad idea
pete at petelancashire.com
Sat Mar 1 17:35:56 EST 2014
not being able to get to my two dead 5370Bs is there enough clearance to
allow for stacking capes ? If not the interface could be a 'horizontal'
implementation. Another one that just came to mind is have holes that
would allow one to put a metal can over the digital blocks / capes /
boards. Holes would go to ground.
On Sat, Mar 1, 2014 at 11:02 AM, John Seamons <jks at jks.com> wrote:
> On Mar 2, 2014, at 7:05 AM, Pete Lancashire <pete at petelancashire.com>
> > Idea. On the next go around for the board put the copper down and holes
> > a couple small daughter cards and any support logic needed to interface
> > with the BBB.
> > The the only additional cost would be limited to the daughter board I/O
> > since my guess it would be SMT hence a bit hard to leave it unpopulated.
> Good idea. Also the Beagle spec allows for multiple, stacked interface
> boards ('capes' they call them). So for a backwards compatible solution an
> experimental GPSDO + backup power cape could be interposed between the
> Beagle and 5370 board. I say experimental because I have no idea if any of
> the SDGPS projects out there would be ultimately suitable for a DO.
> This brings up a question I have about how the PPS edge is actually
> derived by a GPS receiver. Does it originally come from the NAV data stream
> and then get corrected by the (fixed-mode) positioning solution to account
> for transmission/system delays? I know about the issue of alignment with
> the VCTCXO clock, but I'm talking about upstream of that.
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