Re: [ntp:questions] better rate limiting against amplification attacks?
Greg Troxel g...@ir.bbn.com wrote: Really, ntpd should, when run with a config file of only server 0.pool.ntp.org server 1.pool.ntp.org server 2.pool.ntp.org Debian seems to ship the following (minus comments and disabled stuff): driftfile /var/lib/ntp/ntp.drift server 0.debian.pool.ntp.org iburst server 1.debian.pool.ntp.org iburst server 2.debian.pool.ntp.org iburst server 3.debian.pool.ntp.org iburst restrict -4 default kod notrap nomodify nopeer noquery restrict -6 default kod notrap nomodify nopeer noquery restrict 127.0.0.1 restrict ::1 And that seems to work quite well in practice. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Determine from logfiles if PPS/NMEA was discarded?
Hal Murray hal-use...@ip-64-139-1-69.sjc.megapath.net wrote: Try something like: statsdir /var/log/ntp/ filegen protostats type day link That will get you things like: 56672 78792.947 PPS(0) 8054 84 reachable 56672 80327.947 GPS_NMEA(0) 80a3 83 unreachable 56672 80391.944 GPS_NMEA(0) 80b4 84 reachable 56672 80392.944 PPS(0) 8063 83 unreachable 56672 80392.944 PPS(0) 8074 84 reachable You can also get the same info into the normal log file using logconfig xxx but I don't know what the xxx should be. It's in miscopt.html Thanks, I will try! /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Determine from logfiles if PPS/NMEA was discarded?
I've had to rebuild my NTP server, and have had problems of ntp somehow losing the GPS with offsets of 1 second (wrong side of the PPS) and/or huge (100ms+) sporadic jitters since. I'm not sure if I've solved it, but configuring out unneded sentences, fiddling with time2 (400ms now) seems to have vastly improved it, or solved it completely. Is there a way to find out afterwards, if the NMEA has had a problem (e.g. tally x discarded by intersection algorithm, or losing the o of the PPS signal in peer display) while I was not looking? The peerstats/clockstats file is a bit cryptic to me. Thanks in advance, /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] PPS signal from Garmin GPS 18x LVC
Steve Kostecke koste...@ntp.org wrote: In my experience the NMEA driver displays the '*' talley-code even when PPS is in use. Mine does not: remote refid st t when poll reach delay offset jitter == oGPS_NMEA(0) .NMEA. 0 l 13 16 3770.0000.000 0.002 +bevtime1.metrol .ATOM. 1 u- 64 337 18.3001.845 0.649 *ts2.univie.ac.a .PPS.1 u 48 64 377 12.0731.952 0.577 +ntp.liwest.at 131.188.3.2202 u 26 64 3778.4820.554 1.875 (ntpd 4.2.6p5) /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Roof antenna, which one, would you bother?
I am currently in the process of remodeling my house and a dedicated outdoor/roof mounted GPS antenna would be possible to mount without excessive cost. I probably would not see a huge difference for timing purposes, but what would your choice of an outdoor GPS antenna/receiver be? I am planning to put the NTP server (small Raspberry Pi, nothing fancy) into a rack maybe 10 metres of cable length away from the roof. Or would you move the NTP host itself to the attic and run Ethernet up? I suppose something like the Garmin GPS 17x (mast mount GPS with serial output and PPS, intended for the marine market) would work fine, also be robust enough and cheap on the used market. Would mounting just an antenna (active or passive) also make sense, or would cable loss be too high? What would *your* roof top setup be? Cost is of course an important consideration, on the other hand, 100 or 200 Euros for the GPS, antenna and mounting hardware is probably OK. I would prefer to do cabling jobs now, while I am in the process of doing a lot of dirty things. Or would you not bother at all, and just put some puck into the window (which probably works too)? TIA /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Two GPIO PPSes on Raspberry Pi
Has anybody *two* GPIO PPS devices on different GPIO pins on their Raspberry Pi? Would a setup like this enable the ntpd to check the devices against eachother (or probably more likely give an idea of interrupt handling capabilities)? Or does more than one PPS device confuse ntpd? /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] PPS only configuration
Rob nom...@example.com wrote: to use 80-character lines. That was just lazyness and adherance to capabilities of hardware available at the time. No, it was not. It enables formatting text in a sensible way, which is not that easily possible with reflowing text. About 70 characters is also about the most readable line length, be it on screen or in a book. When graphical screens became mainstream, and scalable windows and proportional fonts entered the scene, the 80-character line was obsolete. No, it was not. Just grab any novel from your bookshelf, lines will be about 70 or 80 characters long, most likely. Only, the existing users failed to realize this because they often stuck to existing hardware or emulated existing hardware on new environments. (including running a 80x25 terminal emulator on Windows) The relevant hardware is the ability of the human visual system to follow a line without losing the line. In fact, it has happened again later. Now, people want to read their mail on small phone screens, and again they prefer wrapped paragraphs over fixed line lengths. For the majority of the users there is no problem because they already switched to that system before, but those who want 80-character lines again have a problem. I like to have the same layout on my phone as on the desktop screen. That way I find things easier (adaptive layouts make web pages sometimes look completely different on the phone, making it necessary to learn them again). I prefer to just zoom in and out with the normal desktop layout. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] How exact are the PPS pulses of common GPSses?
After having my Raspberry Pi with PPS running, with an offset and jitter value in the region of 1 to 5 microseconds, I am wondering: How precise is the PPS signal of typical consumer hardware (MTK chips, etc.)? Has anybody hooked up the PPS output of different consumer GPSes to an oscilloscope and compared it against eachother with a precision clock? Is the precision of the PPS pulse higher than what the computer/ntpd daemon can usefully handle, or is the PPS pulse the limiting factor? /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] How exact are the PPS pulses of common GPSses?
Terje Mathisen terje.mathisen at tmsw.no wrote: Unless you replace the motherboard clock source, anything below ~us precision is wasted. Good to know. So basically the 1 or 2µs jitter I get after everything has had time to settle down is the maximum archievable unless you use rather exotic hardware. I have seen reports that the original Motorola Oncore UT+ had something like 30 ns RMS jitter (after applying the sw saw-tooth correction), while the $35 Sure board has been tested by one of the time-nuts people at ~25 ns? That is great, so basically jitter is a non-issue compared to standard computer hardware, and I am pleasantly surprised that the Sure board is that good. Has anybody checked the PPS output for constant shift against UTC? Is it possible that the pulses are off with a constant offset, even if they have very little jitter? Or is this unlikely from what happens inside the receiver? /ralph -- I am waiting for the first tutorial how to build a rubidium-disciplined Raspberry Pi ;) ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Linux/Raspberry Pi: PPS driver loaded, but no PPS devices
james machado hvgeekwt...@gmail.com wrote: you should not need to load the ktimer module to get your PPS working. That is the debug module and fakes PPS to the kernel. Verify that the kernel you installed was an uncompressed kernel. Did you compile it yourself or did you get it off the net? The kernels that come as part of the Raspberry Pi Linux distributions are not able to do PPS and must modified and then recompiled. You can check if your running kernel supports the PPS_GPIO by looking in the /proc/config.gz file (zcat /proc/config.gz | less ) and search for CONFIG_PPS_CLIENT_GPIO it is probably equal to 'm'. If it is not set or doesn't exist then the kernel you are running can not support PPS on the RPi. A delayed thank you for this posting! It was truely helpful, as I was almost going crazy, because my PPS pulse seemingly was placed at a random position against NTP time. Now I know why :) My mistake was compiling the stock Raspbian kernel without the specific gpio-pps patch. The stock kernel can be recompiled to have PPS, only one that did not work for me. The specific patch https://raw.github.com/lampeh/rpi-misc/master/linux-pps/linux-rpi-pps-gpio-bcm2708.diff did it for me. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Does this look sane, is PPS working?
Does this look sane to you for a Raspberry Pi with a Sure Electronics board and PPS enabled? It looks fine to me, I just want to confirm that people more experienced than me see it the same way. remote refid st t when poll reach delay offset jitter == +217.19.37.26.ATOM. 1 u 11 64 377 19.9831.585 0.956 *ts1.univie.ac.a .PPS.1 u 14 64 377 13.6532.661 1.955 -212.33.33.36131.188.3.2202 u 14 64 3778.071 -2.072 1.823 +ts2.univie.ac.a .PPS.1 u 19 64 377 13.7491.864 2.282 oGPS_NMEA(0) .GPS.0 l3 16 3770.000 -0.005 0.001 In root@pi:/home/ralph# ntpq -c rv localhost associd=0 status=0415 leap_none, sync_uhf_radio, 1 event, clock_sync, version=ntpd 4.2.6p5@1.2349 Tue Feb 12 11:35:08 UTC 2013 (1), processor=armv6l, system=Linux/3.6.11, leap=00, stratum=1, precision=-20, rootdelay=0.000, rootdisp=0.388, refid=GPS, reftime=d4c4c966.1eca9efd Tue, Feb 12 2013 15:00:06.120, clock=d4c4c970.3c484545 Tue, Feb 12 2013 15:00:16.235, peer=58223, tc=4, mintc=3, offset=-0.005, frequency=-21.037, sys_jitter=0.001, clk_jitter=0.001, clk_wander=0.001 I do not see any kern, as described by some tutorials. Should I worry about that? Cf. eg.: http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html The relevant section of /etc/ntpd.conf is: server bevtime1.metrologie.at iburst server ts1.univie.ac.at iburst server ntp.liwest.at iburst server ts2.univie.ac.at iburst server 127.127.20.0 mode 24 minpoll 4 maxpoll 4 fudge 127.127.20.0 time2 0.384 flag1 1 TIA /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Does this look sane, is PPS working?
james machado hvgeekwt...@gmail.com wrote: I would expect to see a PPS line if you have PPS up and working correctly, this is what I see on my RPi. I am using the built-in PPS support of the NMEA driver (flag1). associd=0 status=0115 leap_none, sync_pps, 1 event, clock_sync, version=ntpd 4.2.7p347@1.2483 Sat Jan 12 07:12:20 UTC 2013 (1), processor=armv6l, system=Linux/3.6.1+, leap=00, stratum=1, precision=-19, rootdelay=0.000, rootdisp=500.045, refid=PPS, reftime=d4c4e26b.6e1eaad0 Tue, Feb 12 2013 7:46:51.430, clock=d4c4e26e.efc5983d Tue, Feb 12 2013 7:46:54.936, peer=3436, tc=4, mintc=3, offset=-0.002504, frequency=23.052, sys_jitter=0.001907, clk_jitter=0.000, clk_wander=0.001 So no kern either, seems to work anyway ;) fudge 127.127.20.0 time2 0.384 flag1 1 You seem to be missing your PPS driver and should have something similar to this. server 127.127.20.0 mode 16 minpoll 3 iburst prefer fudge 127.127.20.0 flag1 0 time2 0.400 You use the driver 20 (NMEA) without PPS (flag1 0) I (hopefully) use it with (flag1 1). Thanks! The values from your setup are very helpful, as they are quite close to mine. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Does this look sane, is PPS working?
Steve Kostecke koste...@ntp.org wrote: you that your GPS is the PPS peer. Plus the offset and jitter are appropriate for a PPS ref-clock. Thanks that helps a lot. The tally codes are well documented, of course, but I was not quite sure if the offsets against known working NTP servers were acceptable, also that the jitter seems realistic is good to hear. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Using NTP to calibrate sound app
Rob nom...@example.com wrote: I think the average internet connection from a device like an iPhone has so much jitter that this approach will not work reasonably well. (try to ping to an internet server and see what kind of jitter you have, it usually is terrible over UMTS, WiFi etc) iPhones do have a GPS though, and there do exist apps (at least for Android, supposedly also for the iPhone) that sync time to this GPS. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Linux/Raspberry Pi: PPS driver loaded, but no PPS devices
I just got my Sure GPS board, and harware wise it seems to work fine. But i fail to get a PPS from the raspi side. I have recompiled the kernel, installed the modules, and PPS support shows up in dmesg: root@pi:/dev# dmesg | grep PPS [ 13.660962] pps_core: LinuxPPS API ver. 1 registered I do not see a line for the specific PPS device, even though I have loaded the module: root@pi:/dev# cat /proc/modules | grep pps pps_gpio 2219 0 - Live 0xbf076000 pps_core 7978 1 pps_gpio, Live 0xbf07 There is no PPS device: root@pi:/dev# ls /dev/*pp* /dev/ppp /dev/mapper: control I did compile the PPS driver with debugging enabled, but I did not find out how to enable more verbose output. Any hints what I am doing wrong? The PPS output is hooked up, the blue LED is blinking, I have measured a pulse with my voltmeter, so it seems to be a software-side problem. TIA /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Linux/Raspberry Pi: PPS driver loaded, but no PPS devices
Ralph Aichinger ra...@pangea.at wrote: There is no PPS device: Solved, I did not load the ktimer module. Loading it gave me a working pps device. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Looking Terje Mathisen's NMEA-MTK.exe
Hello! I've googled around quite a bit, but did not find a place to download Terje's utility to configure the Sure Electronics GPS (my PPS and NMEA are both marked as falsetickers, so the first thin I want to try is remove the lots of useless sentences sent every second). It is really hard to google up that stuff als there are literally hundreds of scraped Usenet postings polluting the sensible results. TIA /ralph -- email is also valid just in case ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Looking Terje Mathisen's NMEA-MTK.exe
Terje Mathisen terje.mathisen at tmsw.no wrote: I found it where it should be: http://tmsw.no/nmea-mtk.zip Thanks, Terje, veryy much appreciated! /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Using Trimble TSIP under Linux
unruh un...@invalid.ca wrote: But as far as I know, PPS support is in the form of modules. Ie, you should be able to compile those modules separately without doing a full kernel recompile. You can, but you have to take care that it is the same (or at least a very similar) version of the kernel you are compiling the module from as the one you are using to load the module with. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Loopstats jitter field mostly zero?
David Taylor david-tay...@blueyonder.co.uk.invalid wrote: BTW: I would like to get step-by-step instructions for recompiling the kernel with the gpio-pps added, as I'm using someone else's kernel and I may need to make my own when upgrading in the future. I did it with http://elinux.org/RPi_Kernel_Compilation After zcat /proc/config.gz .config in above description, you have to do a make menuconfig where you select the PPS drivers. You find them in Device Drivers -PPS support. Save the configuration, and continue with above step by step instructions. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Audible signal generator (BBC pips)?
As the Raspberry Pi I am currently using as a NTP box has an audio output available, I am wondering if this otherwise unused output (on a dedicated NTP box) could be used to generate BBC style pips or other audible time signals? http://en.wikipedia.org/wiki/Greenwich_Time_Signal As I am probably not the first one to have that idea: Is there software for Linux that does this? Playing a sound file is easy. Playing it in sync with ntpd is a lot harder. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Enclosure for Sure Electronics GPS board
I've ordered a Sure Electronics GPS for my Raspberry Pi. http://www.sureelectronics.net/gallery.php?id=99img=6353 Like the Raspi itself, it is sold without an enclosure. Unlike the Raspi there is not enough of a market for custom cases for this board. As there are several people here using this board: What kind of enclosure are you using? Or are you just using the board naked (which I would rather avoid, as accidents can and will happen, and I am not convinced this board will survive coffeespills or similar)? If there is a case by a manufacturer selling to Europe (like Hammond Electronics, Bopla, Teko) that is a perfect fit, I would be especially happy. I suppose for use without the DB9 serial connector, I just need to drill a larger hole for the mini-USB, another one for the antenna, and a third one for the 4 GPIO connections (GNS, RXD, TXD, PPS)? Bonus points for a flat (not much higher than the board) enclosure. TIA /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Enclosure for Sure Electronics GPS board
David Taylor david-tay...@blueyonder.co.uk.invalid wrote: I used a standard-sized metal box - not very elegant, but at least it provides some shielding (although this is not required). See: http://www.satsignal.eu/ntp/Sure-GPS.htm http://www.satsignal.eu/ntp/sure-GPS-boxed.jpg From: http://www.maplin.co.uk/eddystone-die-cast-aluminium-shallow-lid-thin-wall-43713 That looks very cool, I am a bit scared of making holes in metal cases, though. Even with plastic this can be complicated enough, if you don't have any special tools. I also have a second sure board, inside an anti-static bag, inside a thick black bag (to stop the blue LED's light!). Works fine. Actually I think I will connect another LED and use a non-transparent case, because actually I do want the 1-second blink. But not so bright that it is distracting at night. I suppose connecting another normal red LED to the PPS output cant' be a problem. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Do I have a lock to my NMEA GPS?
Terje Mathisen terje.mathisen at tmsw.no wrote: I.e. the maximum power of the Sure GPS is 0x32 or 50, corresponding to the 100 mA which is guaranteed by the USB 1.0 spec. :-) This is good news for anybody using the Raspberry Pi. So is it actually possible to power the Sure GPS from the Pi USB port in practice, as long as the power supply has enough current for 700mA (the Pi itself)+100mA? Does that really work, has anybody tried? /ralph -- I've ordered one, based on the many postive reviews. It seems a bargain. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Do I have a lock to my NMEA GPS?
Terje Mathisen terje.mathisen at tmsw.no wrote: I would be willing to (make a small) bet that the Pi has to support up to the 500 mA of the 2.0 spec, simply because there are so many peripherals, particuarly USB disks, that require this in order to work at all. No, no, the Raspberry Pi certainly does not supply 500mA. There is a fuse in it that limits total current for the Pi itself and all connected USB peripherials to 1.1A. The Pi itself needs a maximum of 700mA, so if it runs at maximum power there are a maximum of 400mA for USB devices. And that is the maximum, because the fuse has already a somewhat higher resistance at 1.1A, so for weak power supplys the voltage will drop further. There are lots of devices that won't work in the Pi, e.g. most WLAN adapters draw too much current. OTOH, it has to depend on the Pi power supply being big enough. Is there a wall wart or similar in the kit? You are supposed to buy a 700mA (minimum) 5V micro USB power supply. In practice there are good 2A supplies available (for the iPad, e.g.) but the Pi cannot use more than 1.1A from the USB port unless you remove or bypass the main fuse. I really hope that in the next version they test and fuse it for higher current (e.g. 2.1A, that is what iPad chargers supply). Of course the obvious workaround is a powered hub, but that is even more cable mess. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Do I have a lock to my NMEA GPS?
John Hasler jhas...@newsguy.com wrote: The resetable fuses protecting the USB outputs have been removed. This feature was implemented on some later revision 1.0 PCBs by replacing the fuses with links; revision 2.0 permanently implements this modification. It is now possible to reliably power the RPI from a USB hub that back feeds power, but it is important that the chosen hub cannot supply more than 2.5A under fault conditions. I tried backpowering, but at least for me it was completely unstable. Might have been my hubs, as backpowering is a nonstandard use of USB. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Do I have a lock to my NMEA GPS?
Is this OK for a consumer NMEA GPS without PPS (eTrex) and on a jittery USB to serial converter at 4800 Baud? ntpq peers remote refid st t when poll reach delay offset jitter == *GPS_NMEA(0) .GPS.0 l 10 64 3770.000 -87.300 113.691 I don't want to keep time with this, just check if the hardware works. The asterisk in front says I am locked, and hardware is working, does it? TIA /ralph -- a decent PPS GPS will be next ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Do I have a lock to my NMEA GPS?
David Woolley david@ex.djwhome.demon.invalid wrote: You have at least a partial lock. Only time will tell if it is going to stay locked. Your frequency quality wil not be good and your time quality will be worse! Thanks a lot, I just wanted to be sure. The eTrex sends lots of useless crap on the NMEA output, the serial converter is probably a bad idea for more than testing, and I am stress testing my system (Raspberry Pi) at the moment by playing MP3s and sending stuff over another serial adapter. So the high jitter is to be expected. Now I just have to decide between the Adafruit GPS and the Sure Electronics board. Probably the shipping costs will be most relevant. /ralph -- also thanks to Chuck who mailed me! ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Using Trimble TSIP under Linux
David Taylor david-tay...@blueyonder.co.uk.invalid wrote: Thanks, A C. Yes, it's Debian-based, but there's no ntpd.log anywhere on the system. I checked the locations you mentioned and tried the find command. On my Debian system ntpd logs to /var/log/daemon.log together with other daemons: Oct 29 08:11:36 cube ntpd[2964]: ntpd 4.2.6p5@1.2349-o Sat May 12 09:54:55 UTC 2012 (1) Oct 29 08:11:36 cube ntpd[2981]: proto: precision = 0.192 usec /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Using Trimble TSIP under Linux
David Taylor david-tay...@blueyonder.co.uk.invalid wrote: I am at the very early stages of building a small stratum-1 NTP server using a Linux box (Raspberry Pi). A Trimble GPS is connected via USB (yes, I know I will need an interrupt-driven pin for the PPS), and if I install gpsd I can see the output from the GPS with the cgps -s command. I've got a Raspi on order for the same thing: dedicated NTP server. When you get it to run, could you please post how you did it, even if you point out only a few of the hard things? I think I am not the only one who wants to try this, especially power consumption oft the Raspi makes it a likely candidate for servers running 24/7, like ntpd. TIA /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Visual clock display?
This might be a stupid question: What is the best way to visually display the current time of the local ntp server? Currently I am using a small program that uses gettimeofday on my Linux host. As I only want about 100 milliseconds precision, I should be fine. But is there a proper way to display the time of a ntp server continuously on the screen (for timing a clock via photo/video)? TIA /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Visual clock display?
Chris Albertson albertson.ch...@gmail.com wrote: The limit of accuracy of the visual clock is the refresh rate of the monitor. One the old CRT monitors there was a vertical sync that ran at about 60 to 100 Hz. I think LCDs have something like this too. You can do better than 100 mSec using your method. In fact it can approach the vertical sync limit. 100ms is just fine for me, I think. I don't know how much the console driver or a GUI layer adds. The system can do better timing but the 100 Hz (or so) screen refresh is the limit. Actully you eyes can't see a change that is faster than about maybe about 30 mSec. But you CAN see 100 mSec ticks. Run your update loop at 100Hz and you will be fine Is there an official program that displays the time of the ntpd process? Or is one supposed to get time for uses like this from the system clock? Not that I think it makes a difference with 100ms accuracy, but as a matter of principle it would interest me. /ralph ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
