[time-nuts] WWVB teensy BPSK early experiments

[Graham / KE9H]

Paul:

It might be easier to relegate that function to hardware.
A simple TC-VCO that drives the sampling clock for the ADC and is steerable
for frequency/phase lock from the CPU would allow you to build a
synchronous receiver without working about locking the CPU clocking system
to anything.

--- Graham

==

--- Graham

On Mon, Nov 9, 2020 at 8:06 PM paul swed <paulswedb at gmail.com> wrote:

> No time to experiment the last few days as the weather has been great and
> have to get outside stuff done. That said trying to tease apart how to
> create a lockable NCO in the teensy.
> Its not clear to me that I can create a sine wave oscillator and drive that
> out to a pin to see stability and adjustment effects. It can be done by
> mixing with another internal signal and measuring the output. But my
> preference would be direct measurement.
> With respect to sine and cosine. It seems a second oscillator and a third
> oscillator that is 90 degrees out can be created. Supposedly these would be
> locked. (To be proven)
> Regards
> Paul
>
>
> On Sun, Nov 8, 2020 at 7:59 PM John C. Westmoreland, P.E. <
> john at westmorelandengineering.com> wrote:
>
> > Hello Graham and Fellow Time Nuts,
> >
> > I did what Paul had mentioned as well - and that appeared to clear up the
> > immediate screen issues but I will
> > insert a termination resistor as well as Graham has suggested.
> >
> > I looked on the PJRC forum as well - and it appears there has been a lot
> of
> > discussion and development regarding
> > the enhancement of the performance of these TFT displays - also -
> there's a
> > beta version of the arduino libraries -
> > Teensyduino 1.54 Beta #4 -
> > https://forum.pjrc.com/threads/64303-Teensyduino-1-54-Beta-4 - take a
> look
> > at that
> > for those that are experimenting with this platform.
> >
> > As far as my current setup - in the wee hours today - the WWVB signal was
> > coming in very strong - my HPSDR rig
> > using the Clock tool from Multipsk was decoding every minute - the Clock
> > programs' PLL was solidly locked.
> >
> > I noticed for the Teensy4WWVBsdr code it appeared to be in sync with
> WWVB -
> > it was decoding either a minute or
> > the hour apparently correctly - but it was shifted - meaning say for:
> >
> > 2:38:00 AM it decoded 2 as the minute - which was incorrect but correct
> for
> > another time position
> >
> > or, for the hour it would say 8 as hour.  This makes me think obviously
> for
> > some reason the positions are being
> > shifted in an otherwise somewhat successful decode attempt.
> >
> > I am using the Teensy 4.1 - I need to check all of the libs to make sure
> > nothing incompatible is possibly taking place.
> >
> > I've been informed also the antenna from Stormwise is on the way.
> >
> > Thanks again Graham - KE9H - for helping out on this.
> >
> > 73's,
> > John
> > AJ6BC
> >
> >
> > On Sun, Nov 8, 2020 at 8:02 AM Graham / KE9H <ke9h.graham at gmail.com>
> > wrote:
> >
> > > John W:
> > >
> > > Regarding your Teensy WWVB receiver display issues.
> > > The Teensy does not have a source termination resistor on the SPI
> clock.
> > > Add a 50 Ohm resistor (value not critical, anything from 33 to 75 will
> > > work) in series with the SPI Clock signal, as physically close to the
> > > Teensy as practical.
> > > This totally cleared up all of my display issues.
> > > https://www.analog.com/media/cn/training-seminars/tutorials/MT-097.pdf
> > > Source termination resistors provide a source resistance to absorb the
> > > reflection of fast edges off the slave device input, reducing all the
> > > bouncing and wiggles on the rising and falling edges of signals,
> > > particularly important/beneficial on clock signals.
> > >
> > > --- Graham
> > >
> > > ==
> > >
> > >
> > > On Wed, Nov 4, 2020 at 10:55 AM John C. Westmoreland, P.E. <
> > > john at westmorelandengineering.com> wrote:
> > >
> > > > Paul/Chris,
> > > >
> > > > Also - in addition to the white screen, I get this sometimes after
> > > running
> > > > for a while - have you guys seen this?
> > > >
> > > >
> > > >
> > >
> >
> https://user-images.githubusercontent.com/2308903/98118247-cd4c7b00-1e5f-11eb-8510-aa1ed0beba52.jpg
> > > >
> > > > 73's,
> > > > John
> > > > AJ6BC
> > > >
> > > >
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