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@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@gmail.com> >> To: "Discussion of precise time and frequency measurement" <time-nuts@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@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 >>> > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

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@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@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@gmail.com > > > To: "Discussion of precise time and frequency measurement" time-nuts@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@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 > > > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

Does it need to be actual NTP, or could it use a custom broadcast protocol for the 'last yards' ? I'm imagining something that broadcasts a packet subject to the usual anticollision strategies, then in the next packet it reports how far off it actually was (like a GPS sawtooth frame). Some other random thoughts : There are some very small and possibly low-power linux boards around. e.g https://onion.io/store/omega2/ I pinged my laptop over the local (rather outdated but not busy) wifi. Most of the time I got pings in the range 1-3ms. Occasionally there was a 20, 30 or even 90ms response. There is only a single wireless hop and almost no contention (maybe a mobile phone idling) : it's wired from desktop to wireless router. I don't know what causes that but it may be the ESP32 is not doing much worse than anything else. On Mon, Dec 2, 2019 at 8:02 PM Bob kb8tq <kb8tq@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@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@gmail.com> > >> To: "Discussion of precise time and frequency measurement" < > time-nuts@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@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 > >>> > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. >

Hi I’m sitting here getting things set up to start digging into the whole wired / wireless / whatever side of this. The “real” application will be purely WiFi. More or less, the “real” budget is an equal jitter from the server, the client, and the router. If that all comes in under 10 ms, this is wonderful. If it comes out to 30 ms 90% of the time that still works. ==== If indeed “something else” turns out to be the answer, going back to the idea of broadcast NTP would seem to be more attractive than doing something from scratch and plumbing it into a variety of operating systems. ==== Sitting here right now with a quick lash up on an RPi 4, I’m getting jitter numbers in the single digit ms range. I need to get a couple of issues worked out on the local lan before I really trust the data. At the very least it suggests that an RPi 4 client can do pretty well. Bob > On Dec 2, 2019, at 3:48 PM, David Kern <david@mju.io> wrote: > > 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@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@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@gmail.com >>>> To: "Discussion of precise time and frequency measurement" time-nuts@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@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 >>> >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

Does it have to be Wifi ? What about using 315/433MHz or one of the other LIPD bands on an Arduino ? e.g. https://www.instructables.com/id/RF-315433-MHz-Transmitter-receiver-Module-and-Ardu/ regards Tim

Bob, I want to revise my previous statement about ESP8266 WiFi times with some actual measurements. Below are pings to ESP8266 on local Wi-Fi. Most are 0.7ms to 1.1ms with occasional spikes larger than that. PING 192.168.1.13 (192.168.1.13) 56(84) bytes of data. 64 bytes from 192.168.1.13: icmp_seq=1 ttl=255 time=0.877 ms 64 bytes from 192.168.1.13: icmp_seq=2 ttl=255 time=0.881 ms 64 bytes from 192.168.1.13: icmp_seq=3 ttl=255 time=1.97 ms 64 bytes from 192.168.1.13: icmp_seq=4 ttl=255 time=1.11 ms 64 bytes from 192.168.1.13: icmp_seq=5 ttl=255 time=0.936 ms 64 bytes from 192.168.1.13: icmp_seq=6 ttl=255 time=0.805 ms 64 bytes from 192.168.1.13: icmp_seq=7 ttl=255 time=0.760 ms 64 bytes from 192.168.1.13: icmp_seq=8 ttl=255 time=0.826 ms 64 bytes from 192.168.1.13: icmp_seq=9 ttl=255 time=0.838 ms 64 bytes from 192.168.1.13: icmp_seq=10 ttl=255 time=0.850 ms 64 bytes from 192.168.1.13: icmp_seq=11 ttl=255 time=0.898 ms 64 bytes from 192.168.1.13: icmp_seq=12 ttl=255 time=3.07 ms 64 bytes from 192.168.1.13: icmp_seq=13 ttl=255 time=1.06 ms 64 bytes from 192.168.1.13: icmp_seq=14 ttl=255 time=0.986 ms 64 bytes from 192.168.1.13: icmp_seq=15 ttl=255 time=1.03 ms 64 bytes from 192.168.1.13: icmp_seq=16 ttl=255 time=0.792 ms 64 bytes from 192.168.1.13: icmp_seq=17 ttl=255 time=0.885 ms 64 bytes from 192.168.1.13: icmp_seq=18 ttl=255 time=0.883 ms 64 bytes from 192.168.1.13: icmp_seq=19 ttl=255 time=0.815 ms 64 bytes from 192.168.1.13: icmp_seq=20 ttl=255 time=0.869 ms 64 bytes from 192.168.1.13: icmp_seq=21 ttl=255 time=0.777 ms 64 bytes from 192.168.1.13: icmp_seq=22 ttl=255 time=0.880 ms On Mon, Dec 2, 2019 at 9:56 AM Tim Shoppa <tshoppa@gmail.com> wrote: > 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@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 >> >> > On Dec 1, 2019, at 11:18 PM, David Kern <david@mju.io> wrote: >> > >> > I did some testing against an ESP32 this evening to see how feasible it >> would be to use this platform. Unfortunately there is extremely high >> jitter on the wifi interface of the ESP32 (between 4ms to 90ms) - even >> after adjusting some settings and disabling all power management. This was >> testing against a quiet wifi network with consistent 1ms pings between my >> workstation to the router. >> > >> > I believe that high jitter would make it difficult to get a good result >> with NTP over wifi. >> > >> > I'm not sure if the 8266 has the same issue. >> > >> > Shame, because with the ultra low power processor you could do some >> interesting things. >> > >> > -David (AD7WZ) >> > >> > >> > >> > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ >> > On Sunday, December 1, 2019 5:24 PM, Didier Juges <shalimr9@gmail.com> >> wrote: >> > >> >> "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@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@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@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@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@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. >> >>>>>> >> >>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >> >>>>>> To unsubscribe, go to >> >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> >>>>>> and follow the instructions there. >> >>>>> >> >>>>> time-nuts mailing list -- time-nuts@lists.febo.com >> >>>>> To unsubscribe, go to >> >>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> >>>>> and follow the instructions there. >> >>>> >> >>>> time-nuts mailing list -- time-nuts@lists.febo.com >> >>>> To unsubscribe, go to >> >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> >>>> and follow the instructions there. >> >>> >> >>> time-nuts mailing list -- time-nuts@lists.febo.com >> >>> To unsubscribe, go to >> >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> >>> and follow the instructions there. >> >> >> >> time-nuts mailing list -- time-nuts@lists.febo.com >> >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> >> and follow the instructions there. >> > >> > >> > >> > _______________________________________________ >> > time-nuts mailing list -- time-nuts@lists.febo.com >> > To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> > and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> >