On Thu, October 26, 2017 7:38 pm, Denny Page wrote:
> If you are going to do PTP with ptp4l, or NTP with Chrony, you are going
> to want hardware timestamping support on the ethernet phy.
Or the MAC. The processor used on BeagleBone Black has timestamping in
the MAC. Not quite as accurate as sta
On Thu, October 26, 2017 5:58 pm, Bob kb8tq wrote:
> Why go to the green?
Cheaper.
> Just go with one of these Pocket Beagles I have
> sitting here wondering what to do with them.
Pocket Beagles do not have Ethernet. How are you going to make a network
time server from a board with no network?
The 16 bit ADCs (at least the LTC lower sample rate ones ) tend to be a few
dBc/Hz quieter.
However the difference is < 12 dBc/Hz.
Bruce
>
> On 27 October 2017 at 14:35 Li Ang <379...@qq.com> wrote:
>
> Hi
> I just found Andrew recently post a phase noise measruement page on
> ww
Hi
I suspect that once you find a group of chips that do have 1588 embedded in
them that
digging into all the nasty details will take a bit. Time stamping to a 1 ms
resolution might
not be a very helpful thing ….. There are ex-Freescale / now NXP devices that
do have
pretty good 1588 in them. I
If you are going to do PTP with ptp4l, or NTP with Chrony, you are going to
want hardware timestamping support on the ethernet phy. I would view this as
one of the principal concerns in choosing a system.
I’m not sufficiently familiar with Beagles… do any of them support hardware
timestamping?
Hi
I just found Andrew recently post a phase noise measruement page on
www.aholme.co.uk/PhaseNoise/Main.htm .
He uses 4-channel 14bit ADC to do the sampling work. -170dBc noise floor seems
not bad for me.
Since the cross correlation could reduce noise a lot, I am wondering what the
differe
The Thunderbolt, Star-4, Trueposition, and HP GPSDOs/Smartclocks are all known
to do this. Typically the learning period is around 24 hours before the
compensation is allowed to run. My HP GPSDO seems to take a week for best
performance.
Separating tempco and aging drift seems to me to be a r
Hi
Why go to the green? Just go with one of these Pocket Beagle’s I have sitting
here wondering what to do with them. They were just a bit under $20 when I
picked them up. I doubt the price will climb over time …… Indeed you could
get two Pi Zero W’s for the pice of the Pocket Beagle. Lash an int
On 26/10/17 22:11, Chris Caudle wrote:
The processor you mentioned has a Cortex-M7 at 300MHz. has a
Cortex-A8 running at 1GHz plus a Cortex-M processor available as a
coprocessor. Peripheral set is pretty comparable, and you can buy BBB at
retail for $50 which gets you the faster higher cl
Terrific points. There are so many levels of sophistication.
My own experience is with catastrophic signal loss on the reference.
Determining degradation on your primary reference can present
challenges. I once designed a device that compared three Cesiums
and switched the reference within one
On Wed, October 25, 2017 7:53 pm, Nick Sayer via time-nuts wrote:
> I am considering a new project based on its cousin, the ATSAME70.
What is a reasonable cost target for that at the volumes you could
produce? Coming up with something that is a better value than BeagleBone
Black at any kind of ho
Hi
You get into all sorts of issues trying to estimate tempco. You have time lags
and gradients that make it a very messy process. Toss in measurement based on
small range temperature swings (like from a HVAC system) …. it’s a mess.
If the OCXO is a typical modern part and it’s been on power for
Many years ago I tried to add some code to Lady Heather to calculate the
tempco and aging of the oscillator in a normally running Tbolt. Although the
equations would theoretically work (using SVD decomposition) it seldom worked
properly. Failure seemed to be caused by noise in the small num
Hi
So, get it up and running on the 1588 hardware built into one of these “all in
one”
MCU’s should be possible. Note the absence of words like easy or
straightforward :)
Bob
> On Oct 26, 2017, at 12:45 PM, Chris Caudle wrote:
>
> On Thu, October 26, 2017 9:40 am, Bob kb8tq wrote:
>> Since
On Thu, October 26, 2017 9:40 am, Bob kb8tq wrote:
> Since time stamping hardware does exist for 1588, why not simply put the
> effort into folding that into NTP?
According to the Chrony project web page chronyd already includes support
for that.
See "NTP timestamping" section:
https://chrony.tuxf
Hi
Since time stamping hardware does exist for 1588, why not simply put the effort
into
folding that into NTP? Then you have a “generic” solution that addresses a lot
of the
ambiguity a wide range of cases. It shows up in many of the low end micro’s so
it’s
not just a “big box only” solution.
Hi
Most GPSDO’s do some sort of “slew” to an average DAC value when they go into
holdover.
Freezing at the last value is not (in general) a good idea. Often things
degrade before there
is a dropout. Your final DAC value may not be a good one to maximize holdover
duration.
Some setups try to
17 matches
Mail list logo