[time-nuts] BPSK Processing (was First success with very simple, very low cost GPSDO, under $8)

paul swed paulswedb at gmail.com
Mon Apr 21 21:18:49 EDT 2014


Will be travelling on business so will be out of touch next day or two.
Regards
Paul


On Mon, Apr 21, 2014 at 7:35 PM, Chris Albertson
<albertson.chris at gmail.com>wrote:

> I just changed the thread title to "BPSK Processing"
>
> If you are having problems with the software what you need to do is start
> working on it in an easier environment.  That would be some IDE like
> Eclipse on a standard desktop or notebook computer.    You can feed your
> software made-up test data from a text file and send output to the screen.
>   Get this working first them move to the target hardware.    If you write
> in C there is better chance of (1) getting help and (2) finding a library
> to do most of what you want.
>
> But start here by listing (post to this thread) exactly what you expect to
> see as input and what output you'd like to generate.  Seeing real numbers
> rather then some daulitative description is the first step.
>
> Post code examples and ask for advice.
>
>
>
>
> On Mon, Apr 21, 2014 at 1:29 PM, paul swed <paulswedb at gmail.com> wrote:
>
> > Good afternoon very interested in the work you are doing with the STM
> > board.
> > As I mentioned far earlier in this thread I am attempting to use it to
> > correct the BPSK WWVB signal here. Initial thoughts were using FORTH to
> > program the STM board.
> > Very curious what you are using as examples.
> > My experience in FORTH is from many years ago and have done very poorly
> at
> > C. But this may be the case to have something of interest to actually do.
> > In either language.
> > Regards
> > Paul
> > WB8TSL
> >
> >
> > On Mon, Apr 14, 2014 at 12:27 PM, d0ct0r <time at patoka.org> wrote:
> >
> > >
> > >
> > > I was experimenting with the same setup for STM32 MCU. This
> > microprocessor
> > > has accept the sine wave from external OCXO or GPSDO. No problem with
> > this.
> > > The only thing: I was need to start MCU from slow "watch" crystal
> first.
> > > And then switch it to work to external one. In another case I got
> > incorrect
> > > timing settings for MCU. Later, I decide to implement LTC6957-3 chip to
> > > "share" REFCLOCK source, since that chip has two equal CMOS-level
> > outputs.
> > > Unfortunately I have no tool to measure the phase noise and jitters on
> > > each setup.
> > >
> > >
> > >
> > >
> > >  It turns out all of this is built into the AVR chip.   There is a
> > counter
> > >> and logic to copy the current counter value to a register on a PPS
> pulse
> > >> raising edge.    The counter keeps running and every second its value
> is
> > >> trapped.
> > >>
> > >> I can connect the OCXO and the PPS directly to the AVR pin.  The AVR
> has
> > >> hardware (a fast comparator) to "square" a low amplitude sine wave and
> > >> trap
> > >> the counter on a zero crossing.   So it looks like I can get rid of
>  ALL
> > >> of
> > >> the external chips.   The built in DAC is working well also but it
> needs
> > >> some external resisters and caps.
> > >>
> > >> No need for '74 FFs or '373' or counter chips.    I do get precision
> > >> timing
> > >> with no time critical software, no 74xxx chips.
> > >>
> > > --
> > > WBW,
> > >
> > > V.P.
> > >
> > > _______________________________________________
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> > >
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>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
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