Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Hoi Leo, On Thu, 2 Nov 2017 21:45:56 + Leo Bodnar wrote: > I suspect delta-sigma body of knowledge can be applied almost wholesale to > this seemingly silly oscillator concept. > Did I just repeat something trivial that has been discussed to death here > before?

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

d trivial aliases > rejection. > I suspect delta-sigma body of knowledge can be applied almost wholesale to > this seemingly silly oscillator concept. > Did I just repeat something trivial that has been discussed to death here > before? > Leo > >> From: Bob kb8tq &

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

discussed to death here before? Leo > From: Bob kb8tq <kb...@n1k.org> > Subject: Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source > There’s no particular reason to stop at the 100:1 point. You can run multiple > loops at the same time and get out to essentially any le

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Hi There’s no particular reason to stop at the 100:1 point. You can run multiple loops at the same time and get out to essentially any level of precision. The only question is over what averaging interval the precision applies. In some cases this elastic definition does just fine. Bob > On

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

>> The DS3231 has an 8 bit register that will change its frequency in >> increments of about 0.1ppm. Thus you could discipline it to get its pps >> aligned with your reference. > > That sounds like you just designed the worst GPSDO ever. You could argue that the worst GPSDO ever is an operating

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On Thu, Nov 2, 2017 at 9:04 AM, Chris Caudle wrote: > > > That sounds like you just designed the worst GPSDO ever. > > -- > Chris Caudle > > Yes but the price and power consumption are right. I guess it all depends on your application... -- --Jim Harman

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On Wed, November 1, 2017 7:16 pm, Jim Harman wrote: > The DS3231 has an 8 bit register that will change its frequency in > increments of about 0.1ppm. Thus you could discipline it to get its pps > aligned with your reference. That sounds like you just designed the worst GPSDO ever. -- Chris

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On Thu, November 2, 2017 5:19 am, Hal Murray wrote: > I'd let the RTC free run, feed its PPS to a "clock" program, and then feed > the offset to ntpd via SHM. I would just get a GPS that doesn't shut off the PPS when it loses lock and that has a decent TCXO for the clock. Or just use a rubidium

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

mlewis...@rogers.com said: > - GPS module's secondary PPS disciplining the RTC-counter-divider PPS by > resetting the RTC's counter/divider (I'm assuming there's one that will > rest fast enough to sync; I've never looked into these...) How many RTCs accept an external PPS? Your plan sounds

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

tpie...@gmail.com said: > Forget about accurate time from the RTC's registers. The slowness and > variably in I2C is quite poor and most of them don't even have sub-second > resolution when read or written. If your RTC has a PPS output, you can read the registers to get the coarse time, then

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Some of the DS chips have a square wave input that can be fed from a GPS PPS and the RTC will discipline itself. It can also produce a PPS when the GPS stops. The question is, is NTP's holdover on the system clock better than NTP disciplining the system clock with an RTC PPS. I'd guess not.

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On Wed, Nov 1, 2017 at 7:21 PM, MLewis wrote: > > And the DS3231 has: > - a 32K output, and > - an Active-Low-Interrupt/SQW output that can be set to PPS. > It's unclear to me how to sync the DS3231 PPS to the GPS PPS, or if that > can be done. > > > The DS3231 has an 8 bit

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Hi The normal NTP kernel does a pretty good job in “flywheel” mode. For modest outages, it’s quite adequate. Bob > On Nov 1, 2017, at 7:21 PM, MLewis wrote: > > Is this a workable or worthwhile strategy?: > - RTC providing date & time to second to system on boot > -

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Is this a workable or worthwhile strategy?: - RTC providing date & time to second to system on boot - RTC frequency output driving a counter/divider to produce PPS - GPS module providing UTC PPS - GPS module's secondary PPS disciplining the RTC-counter-divider PPS by resetting the RTC's

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

For this apparatus, a lepton is a lepton is a lepton. If the standard model is complete/correct and neutrinos are massless, they can be ignored as a potential threat to our project. They'll just zip through on their way to wherever. The likelihood of a particle interaction is so minute that we can

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Super-lumious or non-speeding neutrinos? Cheers, Magnus On 11/01/2017 04:30 PM, William H. Fite wrote: Oh crap, I forgot about neutrinos. On Wednesday, November 1, 2017, William H. Fite > wrote: Inside a three-meter thick sphere of lead and

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

That sloppy temperaturestabilization??? Also, we would need to care about the lead-poisoning of the mu-metal and the needed re-alignment... ehm... ah well. Cheers, Magnus On 11/01/2017 04:29 PM, William H. Fite wrote: Inside a three-meter thick sphere of lead and mu-metal, pressure pulled

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

This GPS/Pi server, with possibly a second copy, are intended to be the sole NTP sources for a local network. No going out to the internet. My intent was to discipline the RTC, so it's current when needed. If I had to do a cold boot without GPS available, I'd want the RTC to be current. I

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

>> How are you planning on making ntp use the RTC as a secondary >> time source? I don't see that as a supported refclk driver. > hadn't got there yet likely using NTPsec, as the codebase is available if a > driver or generic driver won't work The PPS driver expects the pulse to be on the

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On Wed, November 1, 2017 3:17 pm, MLewis wrote: > hadn't got there yet Your RTC is not likely to be tightly synchronized to NTP time, so there is a high probability that trying to use RTC as a secondary time source will actually make the system worse than just riding through using the NTP

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

hadn't got there yet likely using NTPsec, as the codebase is available if a driver or generic driver won't work https://docs.ntpsec.org/latest/driver_howto.html On 01/11/2017 12:38 PM, Chris Caudle wrote: On Tue, October 31, 2017 9:27 pm, MLewis wrote: I'm intending to add a "precision"

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Tbolt is a good oneBert Kehren Sent from my Galaxy Tab® A Original message From: David J Taylor via time-nuts <time-nuts@febo.com> Date: 11/1/17 12:07 PM (GMT-05:00) To: time-nuts@febo.com Subject: Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source From: Mark S

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

From: David C. Partridge ? RasPi-4? Not released until 2019 AFAIK ... I have RasPi-3 === My Raspberry Pi #1 and Raspberry Pi #4. See: http://www.satsignal.eu/mrtg/performance_ntp.php Cheers, David -- SatSignal Software - Quality software written to your requirements

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

? RasPi-4? Not released until 2019 AFAIK ... I have RasPi-3 -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David J Taylor via time-nuts Sent: 01 November 2017 16:08 To: time-nuts@febo.com Subject: Re: [time-nuts] Holdover, RTC for Pi as NTP GPS

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

From: Mark Sims I have an analytical balance that reads down to micrograms. The weigh chamber is surrounded by three layers of IR absorbing glass so that radiated body heat does not induce convection currents in the air. I worked on a balance that had nanogram resolution (mostly wishful

[time-nuts] Holdover, RTC for Pi as NTP GPS source

I have an analytical balance that reads down to micrograms. The weigh chamber is surrounded by three layers of IR absorbing glass so that radiated body heat does not induce convection currents in the air. I worked on a balance that had nanogram resolution (mostly wishful thinking in that

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Oh crap, I forgot about neutrinos. On Wednesday, November 1, 2017, William H. Fite wrote: > Inside a three-meter thick sphere of lead and mu-metal, pressure pulled > down to .01 mTorr , temperature regulated to .001 degree C, > operating in total darkness and absolute

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Inside a three-meter thick sphere of lead and mu-metal, pressure pulled down to .01 mTorr , temperature regulated to .001 degree C, operating in total darkness and absolute silence, aligned with the galactic axis of rotation, and situated 20 light years from the nearest star. That should

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Hi, On 11/01/2017 04:03 PM, jimlux wrote: On 11/1/17 7:37 AM, Magnus Danielson wrote: Hi,  Silly people want a relative comfortable temperature and well, building A/C is typically bang/bang regulated so you get what you paid for. wouldn't a true time-nut be in a basically isothermal

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Surely he'd want to be in an isolating suit to avoid introducing a nasty warm body into his nice stable cave ? On Wed, Nov 1, 2017 at 3:03 PM, jimlux wrote: > On 11/1/17 7:37 AM, Magnus Danielson wrote: > >> Hi, >> >> Silly people > >> want a relative comfortable

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On 11/1/17 7:37 AM, Magnus Danielson wrote: Hi, Silly people want a relative comfortable temperature and well, building A/C is typically bang/bang regulated so you get what you paid for. wouldn't a true time-nut be in a basically isothermal cave at 10C far underground, and just follow

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Hi, This is also true for labs. One NMI lab I visited had issues with their 5071As and H-maser clocks. It took some time to correlate it, but it turned out to correlate with the florescent lamps in the lab and people walking in and out. Changing these lamps to milder labs removed that

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Hi > On Nov 1, 2017, at 12:14 AM, MLewis wrote: > > (I suspect this is drifting from the original thread too much, so new subject) > > Temperature ranges from 65F to 78F, with the potential for drafts, but is > more typically 76F. The gotcha in a real environment often

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

(I suspect this is drifting from the original thread too much, so new subject) Temperature ranges from 65F to 78F, with the potential for drafts, but is more typically 76F. I read about the NTPsec runs with insulating a Pi and running a load generating program to better maintain a stable