[time-nuts] Lowest Power NTP Server

[Didier Juges]

"Didier, I'm not sure I saw Bob write that 5uS was his goal."

I realize that now, I saw 5uS in another email thread and wrongly
associated the two :) Happens when doing two things at once...
Anyhow, I mentioned it because I did do some experiments early on the
ESP8266 and the seemingly random flash reload was quite unexpected. It was
in the 10's of uS if I recall, so of course not a real concern for this
application but it could be in other cases. Something to keep in mind when
comparing architectures.



On Sun, Dec 1, 2019 at 5:00 PM Tim Shoppa <tshoppa at gmail.com> wrote:

> Didier, I'm not sure I saw Bob write that 5uS was his goal.
>
> I don't think anyone would claim that ordinary cheap WiFi can achieve
> consistent sub-millisecond variations in latency.
>
> Tim N3QE
>
> On Sun, Dec 1, 2019 at 5:06 PM Didier Juges <shalimr9 at gmail.com> wrote:
>
> > You should look at latency. The ESP8266 has serial (SPI) flash and a
> > relatively small internal cache. When the chip needs to load code from
> > flash, that can take a while, compared to the 5uS target. Great for cheap
> > IoT stuff, not so great for time sensitive, in my opinion.
> >
> > On Sun, Dec 1, 2019 at 2:01 PM David <david at mju.io> wrote:
> >
> > > I'd think one of the ESP32's would be a fine choice. They have some
> good
> > > power management options to wake up periodically to do the work, making
> > for
> > > even lower power consumption.
> > >
> > > Looks like someone has already written some code that could be adapted?
> > >
> > > https://github.com/DennisSc/PPS-ntp-server/blob/master/README.md
> > >
> > > -David
> > >
> > > -------- Original Message --------
> > > On Dec 1, 2019, 09:49, Bob kb8tq wrote:
> > >
> > > > Hi
> > > >
> > > > So something like one of the many ESP32 based boards?
> > > >
> > > > Of course when it comes to the “code from scratch” part there is the
> > > problem that I’m
> > > > pretty (most would say very …) lazy :) :) :)
> > > >
> > > > Bob
> > > >
> > > >> On Dec 1, 2019, at 12:29 PM, Poul-Henning Kamp <phk at phk.freebsd.dk>
> > > wrote:
> > > >>
> > > >> --------
> > > >>
> > > >> You can do better than RPi, since a NTP server basically
> > > >> only needs to understand two packets: IP/UDP at port 123
> > > >> and ARP packets.
> > > >>
> > > >> There are WiFi enabled microcontrollers that could be taught how
> > > >> to do that, but you'd have to write up your NTP daemon from scratch
> > > >> which is not hard when you do not have to do the "sync clock from
> > > >> remote servers" part.
> > > >>
> > > >>
> > > >> --
> > > >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
> > > >> phk at FreeBSD.ORG | TCP/IP since RFC 956
> > > >> FreeBSD committer | BSD since 4.3-tahoe
> > > >> Never attribute to malice what can adequately be explained by
> > > incompetence.
> > > >
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