Re: [time-nuts] NEO-M8N vs. NEO-M8T

2018-05-21 Thread Denny Page
On May 21, 2018, at 11:19, Gary E. Miller wrote: > Now, how to I tell the Linux kernel to apply that correction? I honestly don’t understand how this would be used in a meaningful way via the Linux kernel. The nanoseconds of correction for the PPS signal seems a small nit

Re: [time-nuts] Bodnar "Precision Frequency Reference (GPS Clock)" AND LeoNTP Networked Time NTP Server Questions

2018-05-18 Thread Denny Page
Have you considered asking Leo? In my experience, he is very helpful. Denny > On May 17, 2018, at 19:19, Clay Autery wrote: > > Anyone who is using one (or both) of these, and/or folks who have a logical > opinion: > > *"GPSDO"* - Once configured, unit can run on an

Re: [time-nuts] Designing an embedded precision GPS time

2017-11-12 Thread Denny Page
The 6-7us of latency in this discussion does not involve the network path. In this regard network latency is fairly well addressed with hardware timestamping, although trying to get readings across the clock domains looses dozens of nanos of precision. In this discussion, the 6-7us of latency

Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?

2017-11-04 Thread Denny Page
[I hate finding unsent email in my folder :-] Others may disagree, but I doubt that the type of small temperature variation you are referring to has any meaningful effect on tracking. While the datasheet for the M8T says that there can be "significant impact" to the specifications at “extreme

Re: [time-nuts] Designing an embedded precision GPS time

2017-11-01 Thread Denny Page
> On Nov 01, 2017, at 05:39, Attila Kinali wrote: > > 6-10µs is the interrupt latency of linux on ARM SoC. I guess, to get > below that you'd have to tweak the kernel a bit. Which should not > be that difficult. Definitly simpler than writing your own IP and NTP > stack from

Re: [time-nuts] Designing an embedded precision GPS time

2017-10-31 Thread Denny Page
Depends upon the results you are trying to achieve. Using Linux pretty much guarantees that your server clock will be off by 6-10us, with substantial variance. Even with a good nic that supports hardware timestamping, the variance will increase substantially as you go off box (spread spectrum

Re: [time-nuts] Designing an embedded precision GPS time server

2017-10-29 Thread Denny Page
Back to back with 100Mb is good, particularly for latency tests, but you’ll need a switch for general testing. FWIW, an otherwise idle switch generally has very consistent latency, and if both ports are at 100Mb, it is symmetric. Also, with any kind of managed switch you can easily monitor

Re: [time-nuts] NEO-7M various modes

2017-10-28 Thread Denny Page
See the -b and -n options to gpsctl. Also the -b option to gpsd. > On Oct 28, 2017, at 15:12, jimlux wrote: > > Some emit NMEA sentences, others binary (ublox?) strings? ___ time-nuts mailing list -- time-nuts@febo.com To

Re: [time-nuts] Designing an embedded precision GPS time server

2017-10-27 Thread Denny Page
> On Oct 26, 2017, at 19:29, Chris Caudle <ch...@chriscaudle.org> wrote: > > On Thu, October 26, 2017 7:38 pm, Denny Page wrote: >> If you are going to do PTP with ptp4l, or NTP with Chrony, you are going >> to want hardware timestamping support on the et

Re: [time-nuts] Designing an embedded precision GPS time server

2017-10-26 Thread Denny Page
If you are going to do PTP with ptp4l, or NTP with Chrony, you are going to want hardware timestamping support on the ethernet phy. I would view this as one of the principal concerns in choosing a system. I’m not sufficiently familiar with Beagles… do any of them support hardware timestamping?

Re: [time-nuts] Smart Phone time display accuracy...?

2017-03-19 Thread Denny Page
As noted, the device clock’s offset from the current best estimate of correct time is on the second line at the far right. The line that begins with “24”, “AM” or “PM.” If you tap on the offset, it will trigger a re-sync of NTP time. The offset can be based on a single NTP server, so it may

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

2017-02-16 Thread Denny Page
If your Ethernet chipset (mac or phy) has timestamping capabilities, you can use Chrony which has hardware timestamp support. This greatly improves accuracy, and generally eliminates the CPU loading issue. Denny ___ time-nuts mailing list --

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

2017-02-14 Thread Denny Page
> On Feb 14, 2017, at 15:14, J. Grizzard wrote: > > I really recommend the PC Engines apu2c hardware. Just a touch over $100, > schematics available, hardware serial port, GPIO, 1588-capable PHY, CPU > crystal accessible if you want to try a clockblock-type hack,

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

2017-02-14 Thread Denny Page
> On Feb 13, 2017, at 23:47, Hal Murray wrote: > > There is a whole class of low power mother boards targeted at the embedded > market. A few of them have multiple Ethernets - goof for building firewalls. > I haven't found any low cost ones. This one might be of

Re: [time-nuts] wifi with time sync

2017-01-13 Thread Denny Page
It’s a little more complicated than that. A switch’s main cpu is like a host with rx coalesce set to 100. And there are a surprising number of things that trigger the main cpu beyond management functions. Multicast is a good example. The amount of load on the main cpu can be quite variable, and

Re: [time-nuts] wifi with time sync

2017-01-13 Thread Denny Page
> On Jan 13, 2017, at 09:40, Bob Camp wrote: > > Just for reference, I happen to be running a ping over my local WiFi to one > of the switches > on the LAN. The ping response is anywhere from 2 ms out to 400 ms. Most of > the time it’s > in the 3 to 9 ms range. Simply taking