Re: [time-nuts] iPhone keeping better time?
From: Doug Calvert [] It is still the reference implementation just with different defaults. I also think the minpoll is ridiculously high. If you add your own servers / config directives below the line that the GUI adds to /private/etc/ntp.conf things work fine. I had autokey working on one up until the most recent autokey change. Pedantically, still the reference implementation, but outside the spirit and best practice which has evolved over the years. It seems that neither the iPhone not the iPad run anything resembling the reference implementation. At least with iOS 5.0.1 my iPad is only 1.259 seconds off, rather than the minutes it was before - making it useless for satellite passes! Thanks for your information. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
On 11/16/2011 10:03 AM, David J Taylor wrote: I own a Mac Mini and a MacBook. Their NTP implementation is simply a joke. Even with a local stratum 1 I can't get decent accuracy. :-( David, weren't you interested in a LED clock I was going to build? Cheers, Miguel A pity that there isn't a port of the reference NTP for the Mac, such as we have on Windows. What? OSX has a slightly dated version of the NTP ref implementation. It looks like it is 4.2.6: http://opensource.apple.com/source/ntp/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
On 11/16/2011 12:28 PM, David J Taylor wrote: Apple run their own NTP servers and ship their Macs configured to use them to sync time. Last time I looked those servers were either not working, or very broken! Apple should use the pool rather than create single poinst of failure. Their servers were not so bad the last time i monitored them. the time.apple.com servers are stratum 2s. I think they sync to tick and tock.apple.com in the us and the euro hosts sync with truetime.euro.apple.com. I never bothered looking for the stratum one server for the time.asia group. dfc@ronin:/var/repos/ntp-dev$ host time.apple.com time.apple.com has address 17.151.16.23 time.apple.com has address 17.151.16.22 time.apple.com has address 17.151.16.21 time.apple.com has address 17.151.16.20 time.apple.com has address 17.151.16.30 time.apple.com has address 17.151.16.28 time.apple.com has address 17.151.16.31 time.apple.com has address 17.151.16.29 time.apple.com has address 17.171.4.24 time.apple.com has address 17.171.4.22 time.apple.com has address 17.171.4.23 time.apple.com has address 17.171.4.21 dfc@ronin:/var/repos/ntp-dev$ host time.euro.apple.com time.euro.apple.com has address 17.72.255.11 time.euro.apple.com has address 17.72.255.12 dfc@ronin:/var/repos/ntp-dev$ host time.asia.apple.com time.asia.apple.com has address 17.82.253.7 time.asia.apple.com has address 17.83.253.7 Apple should use the pool? Apple should support/donate/take part in the pool. But it would not be apple if they did not think different:) I believe the Mac NTP client is shipped with a very large maximum polling interval. Try reducing it. In which case they are not running the reference implementation, as the polling interval should automatically adjust to suit the need, and not normally require the user to fiddle with the settings. It is still the reference implementation just with different defaults. I also think the minpoll is ridiculously high. If you add your own servers / config directives below the line that the GUI adds to /private/etc/ntp.conf things work fine. I had autokey working on one up until the most recent autokey change. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
On 11/16/2011 11:14 AM, Mike S wrote: At 10:03 AM 11/16/2011, David J Taylor wrote... A pity that there isn't a port of the reference NTP for the Mac, such as we have on Windows. macmini-2:~ mikes# ntpd --version ntpd - NTP daemon program - Ver. 4.2.4p4 Seems to be the standard implementation. Works fine for me. I think that is not the most recent OSX release right? The opensource.apple.com page seems like 4.2.6 is the most recent... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
I'm currently using a Samsung Galaxy S II, which I'm very impressed with. Have just found an NTP client on the Android Market which seems to work OK. Will investigate further. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: 16 November 2011 18:35 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] iPhone keeping better time? I doubt we will ever see good time keeping on an IOS type device. The problem is battery life. Good time keeping requires a stable local oscillator of some kind that must remain powered up 24x7. But to get the long battery life they must power off everything they possibly can. No mater how far technology advances it will always require less power to not ruin an oscillator then to run one. I doubt Apple would run NTP in an iPhone. They don't want to multi task the CPU and there is no stable local oscillator to be disciplined. On Wed, Nov 16, 2011 at 10:21 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: It's even worse on the WiFi iPad - there is no way to automatically set the time. You can only do it via the Settings page and that only gives you minute resolution. The Emerald-Sequoia app is nice, but since it can't actually fix the time, every app that has time constraints has to do its own NTP. Criminal, really! Even SNTP would be better. I had hoped it would be fixed in iOS 5.0 as I'd seen it discussed in the beta groups. David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Just how bad is it using network time? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
On 16 November 2011 12:27, Jim Palfreyman jim77...@gmail.com wrote: Folks, Is it my imagination or is the iPhone under IOS 5 keeping way better time? Mine (3 GS running 5.0.1) is apparently within 1 second of UTC which is good. By the way... is it possible to build a custom receiver to send this information to a computer? I live in Europe so there's only GSM available... Do the US CDMA receivers work here? Cheers, Miguel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Folks, Is it my imagination or is the iPhone under IOS 5 keeping way better time? I assume it's contacting the mobile towers more often for reading time. Jim Palfreymam Lucky Jim! Certainly doesn't apply to my iPad2. Currently 40.8 seconds out under 5.0.1. Sinful it doesn't use NTP ( I suppose you know who didn't approve of NTP, since it wasn't under Apple's firm grip). At least Emerald Sequoia's Emerald Time application allows one to see the error! Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
On 16 November 2011 12:47, David J Taylor david-tay...@blueyonder.co.ukwrote: Folks, Is it my imagination or is the iPhone under IOS 5 keeping way better time? I assume it's contacting the mobile towers more often for reading time. Jim Palfreymam Lucky Jim! Certainly doesn't apply to my iPad2. Currently 40.8 seconds out under 5.0.1. Sinful it doesn't use NTP ( I suppose you know who didn't approve of NTP, since it wasn't under Apple's firm grip). I own a Mac Mini and a MacBook. Their NTP implementation is simply a joke. Even with a local stratum 1 I can't get decent accuracy. :-( David, weren't you interested in a LED clock I was going to build? Cheers, Miguel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
I own a Mac Mini and a MacBook. Their NTP implementation is simply a joke. Even with a local stratum 1 I can't get decent accuracy. :-( David, weren't you interested in a LED clock I was going to build? Cheers, Miguel A pity that there isn't a port of the reference NTP for the Mac, such as we have on Windows. Yes, Miguel, someone did mention an NTP synched clock some time back, and I thought it might be a fun project. Based on an Arduino board IIRC? Although I don't think it had Wi-Fi by default Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
I use an app. that is called Emerald Sequoia that pings Internet time servers and I find my iPhone 4 with IOS 5 is off by about 1-2 seconds. Cheers Raj Folks, Is it my imagination or is the iPhone under IOS 5 keeping way better time? I assume it's contacting the mobile towers more often for reading time. Jim Palfreymam ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
At 07:27 AM 11/16/2011, Jim Palfreyman wrote... Is it my imagination or is the iPhone under IOS 5 keeping way better time? I assume it's contacting the mobile towers more often for reading time. My Android phone is consistently 1 second behind GPS (CDMA network) time. That is, it's 14 seconds ahead of UTC. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
At 10:03 AM 11/16/2011, David J Taylor wrote... A pity that there isn't a port of the reference NTP for the Mac, such as we have on Windows. macmini-2:~ mikes# ntpd --version ntpd - NTP daemon program - Ver. 4.2.4p4 Seems to be the standard implementation. Works fine for me. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Yes, Miguel, someone did mention an NTP synched clock some time back, and I thought it might be a fun project. Based on an Arduino board IIRC? Although I don't think it had Wi-Fi by default I have it running at the moment. Have to build a case tough. See attached picture. It looks very smart! It syncs at the 9th, 19th, 29th, ... second mark from a local GPS based NTP server. On every sync, the timestamp returned from the NTP server is on the 6 ms mark this means that the local clock of the Arduino drifts a lot. 6 ms per 10 s. Outside the 500 ppm allowed for NTP! G I am installing a realtime clock (Chronodot) this weekend that has an accuracy of +/- 3.5 ppm from -40C to 85C (I read somewhere that between 0 and 40C it is 2 ppm). This RTC can output a square wave signal at 1 Hz and Arduino can read that and use it to update the display at the exact second mark. With the RTC and synching every 10 minutes (9th, 19th, 29th, 39th, 49th and 59th of every hour) I expect a maximum error of 1.2 ms (based on 2 ppm). My eyes can't read that :-) Nor mine! On my PC, the radio pips, and the hands on the analogue clock I wrote, appear to be precisely in sync, but I expect that means within a few tens of milliseconds. A neat feature I added is that when the clock can't synch it won't show a time. It will show -- : --. Shouldn't that be the classic video recorder display? A flashing 00:00 or whatever? I also have code that enables the user to telnet to the clock's IP address and change its setting which are saved in the Arduino EEPROM. If you are interested in a parts list and even the code I can send it to you next week as soon as I add the RTC The most interesting part is that buying a clock from Inova ( http://www.inovasolutions.com/network-clocks/products/digital-network-clock.htm) would cost be 5 times more and it would not be as accurate as this one. Cheers, Miguel Yes, I would be interested, but others might as well, so perhaps put it up on the Web somewhere? Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Hi David! On 16 November 2011 16:18, David J Taylor david-tay...@blueyonder.co.ukwrote: Yes, Miguel, someone did mention an NTP synched clock some time back, and I thought it might be a fun project. Based on an Arduino board IIRC? Although I don't think it had Wi-Fi by default I have it running at the moment. Have to build a case tough. See attached picture. It looks very smart! I have a small plate of frosted plexiglass in front of the display to diffuse the strong light of the LED. I am about 4 meters away from it and it looks great. The digits are 29 mm tall while with 5 mm LED they would be 50 mm tall. Too big for my office but perhaps some might want larger digits. It syncs at the 9th, 19th, 29th, ... second mark from a local GPS based NTP server. On every sync, the timestamp returned from the NTP server is on the 6 ms mark this means that the local clock of the Arduino drifts a lot. 6 ms per 10 s. Outside the 500 ppm allowed for NTP! G A bit too much... The RTC will help a lot. Actually, the RTC performance is great. 2 ppm means 0.02 ms every 10 seconds (0.12 ms every minute). Not bad! With 3 local GPS stratum 1 servers peered together I can pool them every 10 seconds and maintain sub ms accuracy. Inova clocks talk about 200 ms accuracy. Even with Internet NTP servers and pooling every 5 minutes the accuracy of this RTC would be 0.6 ms. 200 times better than the commercial product. I don't understand why a company like Meinberg sells these clocks! I am installing a realtime clock (Chronodot) this weekend that has an accuracy of +/- 3.5 ppm from -40C to 85C (I read somewhere that between 0 and 40C it is 2 ppm). This RTC can output a square wave signal at 1 Hz and Arduino can read that and use it to update the display at the exact second mark. With the RTC and synching every 10 minutes (9th, 19th, 29th, 39th, 49th and 59th of every hour) I expect a maximum error of 1.2 ms (based on 2 ppm). My eyes can't read that :-) Nor mine! On my PC, the radio pips, and the hands on the analogue clock I wrote, appear to be precisely in sync, but I expect that means within a few tens of milliseconds. :-) Perhaps we both need to wear glasses :-) A neat feature I added is that when the clock can't synch it won't show a time. It will show -- : --. Shouldn't that be the classic video recorder display? A flashing 00:00 or whatever? 00:00 flashing... done! I'll post a video for you to see soon. You'll tell me if you like it or not. You'll be my beta tester :-) Yes, I would be interested, but others might as well, so perhaps put it up on the Web somewhere? I'll do that as soon as possible. Cheers, Miguel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Miguel Gonçalves m...@miguelgoncalves.com wrote: On 16 November 2011 12:47, David J Taylor david-tay...@blueyonder.co.ukwrote: Certainly doesn't apply to my iPad2. Currently 40.8 seconds out under 5.0.1. Sinful it doesn't use NTP ( I suppose you know who didn't approve of NTP, since it wasn't under Apple's firm grip). Apple run their own NTP servers and ship their Macs configured to use them to sync time. I own a Mac Mini and a MacBook. Their NTP implementation is simply a joke. Even with a local stratum 1 I can't get decent accuracy. :-( I believe the Mac NTP client is shipped with a very large maximum polling interval. Try reducing it. Also, ntpd does not work well on machines that are often suspended. I don't know if Apple have done anything to fix that. Tony. -- f.anthony.n.finch d...@dotat.at http://dotat.at/ Viking, North Utsire, South Utsire, Forties, Cromarty, Forth, Tyne, Dogger, Fisher, German Bight, Humber: Southerly or southeasterly 4 or 5, occasionally 6 except in German Bight and Humber. Moderate, but becoming rough later in northwest Viking. Drizzle at times. Moderate or good, occasionally poor.___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
On Wed, Nov 16, 2011 at 7:03 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: A pity that there isn't a port of the reference NTP for the Mac, such as we have on Windows. As I remember you simply compile NTP on the Mac and it just worked. No need for a port. Has something changed?Mac OS is really just BSD with a big bunch of layered software on top. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Le 16/11/2011 18:33, Chris Albertson a écrit : On Wed, Nov 16, 2011 at 7:03 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: A pity that there isn't a port of the reference NTP for the Mac, such as we have on Windows. As I remember you simply compile NTP on the Mac and it just worked. No need for a port. Has something changed?Mac OS is really just BSD with a big bunch of layered software on top. Even out of the box, my Macbook with OSX10.6 is fine. I just imported my home farm ntp config. I am running over ether and not wifi . Maybe that would have some adverse effect. I'll pull the plug and check. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
As I remember you simply compile NTP on the Mac and it just worked. No need for a port. Has something changed?Mac OS is really just BSD with a big bunch of layered software on top. Chris Albertson I'd looked for a download, and not found one. I cannot imagine the typically portrayed Mac (or PC) user compiling NTP for themselves. But if it's installed by default, and correctly configured, it's not an issue. Lack of good timekeeping on the iPhone or iPad is an unnecesaary inconvenience in use. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
It's even worse on the WiFi iPad - there is no way to automatically set the time. You can only do it via the Settings page and that only gives you minute resolution. The Emerald-Sequoia app is nice, but since it can't actually fix the time, every app that has time constraints has to do its own NTP. On Wed, Nov 16, 2011 at 12:58 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: As I remember you simply compile NTP on the Mac and it just worked. No need for a port. Has something changed?Mac OS is really just BSD with a big bunch of layered software on top. Chris Albertson I'd looked for a download, and not found one. I cannot imagine the typically portrayed Mac (or PC) user compiling NTP for themselves. But if it's installed by default, and correctly configured, it's not an issue. Lack of good timekeeping on the iPhone or iPad is an unnecesaary inconvenience in use. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
It's even worse on the WiFi iPad - there is no way to automatically set the time. You can only do it via the Settings page and that only gives you minute resolution. The Emerald-Sequoia app is nice, but since it can't actually fix the time, every app that has time constraints has to do its own NTP. Criminal, really! Even SNTP would be better. I had hoped it would be fixed in iOS 5.0 as I'd seen it discussed in the beta groups. David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
On 16 November 2011 18:21, David J Taylor david-tay...@blueyonder.co.ukwrote: It's even worse on the WiFi iPad - there is no way to automatically set the time. You can only do it via the Settings page and that only gives you minute resolution. The Emerald-Sequoia app is nice, but since it can't actually fix the time, every app that has time constraints has to do its own NTP. Criminal, really! Even SNTP would be better. I had hoped it would be fixed in iOS 5.0 as I'd seen it discussed in the beta groups. IMHO, in Mac OS X it is worse to have a bad NTP client installed by default than no NTP client at all. Cheers, Miguel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
I doubt we will ever see good time keeping on an IOS type device. The problem is battery life. Good time keeping requires a stable local oscillator of some kind that must remain powered up 24x7. But to get the long battery life they must power off everything they possibly can. No mater how far technology advances it will always require less power to not ruin an oscillator then to run one. I doubt Apple would run NTP in an iPhone. They don't want to multi task the CPU and there is no stable local oscillator to be disciplined. On Wed, Nov 16, 2011 at 10:21 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: It's even worse on the WiFi iPad - there is no way to automatically set the time. You can only do it via the Settings page and that only gives you minute resolution. The Emerald-Sequoia app is nice, but since it can't actually fix the time, every app that has time constraints has to do its own NTP. Criminal, really! Even SNTP would be better. I had hoped it would be fixed in iOS 5.0 as I'd seen it discussed in the beta groups. David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
I doubt we will ever see good time keeping on an IOS type device. The problem is battery life. Good time keeping requires a stable local oscillator of some kind that must remain powered up 24x7. But to get the long battery life they must power off everything they possibly can. No mater how far technology advances it will always require less power to not ruin an oscillator then to run one. I doubt Apple would run NTP in an iPhone. They don't want to multi task the CPU and there is no stable local oscillator to be disciplined. Chris, I can see your point, but these devices must have a CPU running all the time, otherwise how would the soft power-up work? Can the drain of a CMOS clock chip such as that used in millions of PCs be all that much more? But suppose there is no clock, even just one SNTP sync when starting or reconnecting to the network would make the iPad a far better timekeeper - no need for full NTP. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Modern CPUs typically change their clock speeds and can go real slow while idle. This is why modern PCs keep so much worse time than their 1990s ancestors. On Wed, Nov 16, 2011 at 2:56 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: I doubt we will ever see good time keeping on an IOS type device. The problem is battery life. Good time keeping requires a stable local oscillator of some kind that must remain powered up 24x7. But to get the long battery life they must power off everything they possibly can. No mater how far technology advances it will always require less power to not ruin an oscillator then to run one. I doubt Apple would run NTP in an iPhone. They don't want to multi task the CPU and there is no stable local oscillator to be disciplined. Chris, I can see your point, but these devices must have a CPU running all the time, otherwise how would the soft power-up work? Can the drain of a CMOS clock chip such as that used in millions of PCs be all that much more? But suppose there is no clock, even just one SNTP sync when starting or reconnecting to the network would make the iPad a far better timekeeper - no need for full NTP. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Message: 5 Date: Wed, 16 Nov 2011 10:35:01 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] iPhone keeping better time? Message-ID: cabbxvhs6fltsfe_miysvxb0jowrzdacwgy7xjmov34sjhad...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 I doubt we will ever see good time keeping on an IOS type device. The problem is battery life. Good time keeping requires a stable local oscillator of some kind that must remain powered up 24x7. But to get the long battery life they must power off everything they possibly can. No mater how far technology advances it will always require less power to not ruin an oscillator then to run one. I doubt Apple would run NTP in an iPhone. They don't want to multi task the CPU and there is no stable local oscillator to be disciplined. Ugh. Yes, iOS devices sip power by turning as much of itself off whenever it can. However, iOS is still running a version of the XNU kernel: http://en.wikipedia.org/wiki/XNU That kernel *does* multitask. The multitasking you're referring to is what is allowed by apps that are run at the high layers of the system. There are system daemons that do run, though ntpd is not one of them, probably for the exact reasons you mention about saving on battery usage. The times you see on phone network based iOS devices come from the cell phone time keeping (on older devices) and then GPS (on later devices with actual GPS parts) (i.e. if the time is off, it could be the cell provider's fault). See also: [1] http://code.google.com/p/ios-ntp/wiki/WhatsItAllAbout [2] http://www.quora.com/Will-iOS-5-Support-NTP-so-that-the-iPad-can-keep-time Under iOS 5, you can tell an iOS device to automatically set its time and it appears to use a very simple timed to do it, see the second reference. On Wed, Nov 16, 2011 at 10:21 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: It's even worse on the WiFi iPad - there is no way to automatically set the time. ?You can only do it via the Settings page and that only gives you minute resolution. The Emerald-Sequoia app is nice, but since it can't actually fix the time, every app that has time constraints has to do its own NTP. Criminal, really! ?Even SNTP would be better. ?I had hoped it would be fixed in iOS 5.0 as I'd seen it discussed in the beta groups. David -- SatSignal software - quality software written to your requirements Web: ?http://www.satsignal.eu Email: ?david-tay...@blueyonder.co.uk -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Chris, I can see your point, but these devices must have a CPU running all the time, otherwise how would the soft power-up work? Can the drain of a CMOS clock chip such as that used in millions of PCs be all that much more? CPU chips used in battery powered systems typically have a way to turn off the CPU until an interrupt arrives. If you are serious, you turn off the CPU clock too. That means you can only get woken up by the CMOS clock or an I/O device that has it's own clock. Yes, it takes time (few ms) to turn the clock back on. The numbers are impressive. If you use SRAM rather than DRAM, you don't need memory refresh. Many modern ARM chips include flash and SRAM. They aren't big enough for a phone full of bloatware, but the idle current is hard to measure. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Le 16/11/2011 18:42, mike cook a écrit : Le 16/11/2011 18:33, Chris Albertson a écrit : On Wed, Nov 16, 2011 at 7:03 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: A pity that there isn't a port of the reference NTP for the Mac, such as we have on Windows. As I remember you simply compile NTP on the Mac and it just worked. No need for a port. Has something changed?Mac OS is really just BSD with a big bunch of layered software on top. Even out of the box, my Macbook with OSX10.6 is fine. I just imported my home farm ntp config. I am running over ether and not wifi . Maybe that would have some adverse effect. I'll pull the plug and check. As expected , over wifi it sucks . ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
m...@miguelgoncalves.com said: On every sync, the timestamp returned from the NTP server is on the 6 ms mark this means that the local clock of the Arduino drifts a lot. I am installing a realtime clock (Chronodot) this weekend that has an accuracy of +/- 3.5 ppm from -40C to 85C (I read somewhere that between 0 and 40C it is 2 ppm). This RTC can output a square wave signal at 1 Hz and Arduino can read that and use it to update the display at the exact second mark. How does the timekeeping on the Arduino work? My guess is that there is an interrupt that does something like: time = time + delta where delta is calculated from the interrupt frequency. The first step is to make sure the software is doing the arithmetic correctly. A common bug in that area is to be using the wrong value of delta. You may need to fix the code to handle fractional parts of delta. The code is simple after you see it. It's just standard multi-precision integer arithmetic with the decimal point in the middle rather than the right end. The code is roughly: time = time + delta; fraction = fraction + delta2; if (overflow) time = time + 1; You may need to handle delta2 being negative. You need enough bits in fraction so the bottom bit can represent the accuracy you want. 1 PPM is good for a second per week. If you are a time-nut, you probably want better than that. There is no point in going overboard unless your temperature is very stable. I'd probably shoot for PPB but be happy with several bits closer to PPM if that was convenient. The second step is is to adjust delta2 to match what your crystal is actually doing. You could measure it with a counter and calculate, or let it run long enough so you can see the difference with a scope on the update to the LED display compared to something known-good like a PPS signal. If it's way out, you can probably see the drift on a clock display. You just have to wait long enough. -- Old story: I started working for Xerox back in 1976. Shortly after I got there, Ed Taft fixed a bug in the Alto timekeeping code. The system was designed around a 170 ns cycle time. Oscillators come in megahertz rather than nanaoseconds, so they ordered 5.88 MHz crystals. The software used 170 ns. If I did the math right, the difference is 340 ppm. That's enough to be annoying, but good enough that it won't be noticed during the early stages of software development. The Altos reset their time from a time server on each reboot. That happened often enough to hide the problem for a while. Back in those days, we calibrated the crystal on the time servers by hand. The config file had the correction in seconds per day. (I think.) You could get the rough calibration in a day and much better if you waited a week. Mostly, they were in air-conditioned machine rooms. In hindsight, it was primitive, but it worked well enough. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
On Wed, Nov 16, 2011 at 11:56 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: Chris, I can see your point, but these devices must have a CPU running all the time, otherwise how would the soft power-up work? The ARM processor has a power manager that wakes the CPU and powers it up when events like a WiFi packet comes in or there is some input by the user. The CPU is not left running. watching for these kind of evens is done by a much smaller chip Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
See also: [1] http://code.google.com/p/ios-ntp/wiki/WhatsItAllAbout [2] http://www.quora.com/Will-iOS-5-Support-NTP-so-that-the-iPad-can-keep-time Under iOS 5, you can tell an iOS device to automatically set its time and it appears to use a very simple timed to do it, see the second reference. Thanks, Colby. From the first reference I found: Settings General Date Time has a Set Automatically now Settings Location Services System Services has a Setting Time Zone and now I'm a happy bunny! I had looked for this in the iOS 5 info, but not found it. By default it was not set on my iPad2 (upgraded from iOS 4) Now only about 0.6 seconds out! Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone keeping better time?
Chris, I can see your point, but these devices must have a CPU running all the time, otherwise how would the soft power-up work? The ARM processor has a power manager that wakes the CPU and powers it up when events like a WiFi packet comes in or there is some input by the user. The CPU is not left running. watching for these kind of evens is done by a much smaller chip Chris Albertson Redondo Beach, California Thanks, Chris. That's why I wrote a CPU rather than the CPU. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
