[time-nuts] Lowest Power NTP Server

[David Kern]

Bob,

Will all the devices and the NTP server be connecting to an already existing Wifi AP - or is there a possibility that the Wifi AP itself provides the NTP service?

When I did more testing, I discovered that it isn't just ESP32s that do weird things on WiFi - when pinging from something on wifi to wired, I got consistent fast pings.  But when pinging from something on wifi to something else on wifi then I got the strange latency issues where it would spike and end up all over the place.  I'm a bit stumped as to why at the moment, maybe it is something weird with my network.

But at any rate - if the AP in your setup could handle timekeeping, then it eliminates one of the hops and part of the jitter.

There are a bunch of off-the-shelf wifi routers that can be flashed with a more capable linux environment and are already DC powered.

(As an aside, there was mention of adding time distribution over wifi by hacking the protocol a bit.  Does anyone recall how this would work - like doing something with the beacon frames or sending some special frame on the channel?)

-David (AD7WZ)




‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Monday, December 2, 2019 11:51 AM, Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> Wired is out for this particular setup. It needs to be some sort of wireless. It all would
> be much more simple with wires.
>
> Bob
>
> > On Dec 2, 2019, at 12:46 PM, Robert LaJeunesse lajeunesse at mail.com wrote:
> > If wired Ethernet seems to be the way to go consider the Orange Pi Zero - about the cheapest wired Ethernet board available that runs Linux. Ethernet is via on-chip MAC and phy, so no USB path delays. http://www.orangepi.org/orangepizero/
> > Plenty of support exists on the web, for example: https://lucsmall.com/2017/01/19/beginners-guide-to-the-orange-pi-zero/
> > Bob L.
> >
> > > Sent: Monday, December 02, 2019 at 9:56 AM
> > > From: "Tim Shoppa" tshoppa at gmail.com
> > > To: "Discussion of precise time and frequency measurement" time-nuts at lists.febo.com
> > > Subject: Re: [time-nuts] Lowest Power NTP Server
> > > Bob, I find that 2.4GHz Wi-Fi UDP latency with ESP8266 will frequently be
> > > tens of milliseconds and is never/rarely consistent.
> > > There are specialized non-WiFi 2.4GHz systems for time distribution that
> > > are far more consistent (possibly even at the tens of microseconds). I
> > > think several years ago on this list, we were talking about tricking
> > > commodity WiFi chipsets into doing these but haven't seen anything as of
> > > late.
> > > Tim N3QE
> > > On Mon, Dec 2, 2019 at 8:02 AM Bob kb8tq kb8tq at n1k.org wrote:
> > >
> > > > Hi
> > > > Indeed, if you get up into the “many tens” of ms, that rules it out in my
> > > > application.
> > > > A consistent 90 ms would be ok, you could compensate for that. Random
> > > > flopping
> > > > from 4 to 90 … not so much.
> > > > It seems like that sort of jitter would get in the way of a lot of things.
> > > > I guess that just
> > > > shows how little I know about a lot of things :)
> > > > Bob
> >
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