Re: [chrony-users] GPS / Chrony NTP server config questions

On Thu, Nov 16, 2017 at 01:40:12PM -0800, Bill Unruh wrote: > On Thu, 16 Nov 2017, Rob Janssen wrote: > > For really accurate PPS handling one would want a dedicated PCI-E card > > with a clock oscillator and a counter, > > latched in a register on PPS edge, and issuing the interrupt. The > >

Re: [chrony-users] GPS / Chrony NTP server config questions

I thought i might add my own $0.02 as this is something i've been working on for some time (i.e. trying to figure out which gps module is best for my OSH project). The MTK3339 is ok, but my current round of hardware design has been putting the neo6m, Quectel L80 and MTK3339 up against each

Re: [chrony-users] GPS / Chrony NTP server config questions

Bill Unruh wrote: All of those systems have an "onboard UART". Setserial determines them as: /dev/ttyS0 at 0x03f8 (irq = 4) is a 16550A However there is of course no 16550A anywhere on those boards, it is a cell in some system support chip. It is true that parallel is better than serial, if

Re: [chrony-users] GPS / Chrony NTP server config questions

On Thu, 16 Nov 2017, Rob Janssen wrote: Bill Unruh wrote: I am using chrony with serial PPS on a number of different machines, and I see the 6-7 us figure on HP Proliant systems while on Dell PowerEdge sytems it is more like 1us. No idea where the difference comes from. How do you

Re: [chrony-users] GPS / Chrony NTP server config questions

On Thu, 16 Nov 2017, Denny Page wrote: On Nov 16, 2017, at 10:32, Bill Unruh wrote: On Thu, 16 Nov 2017, Denny Page wrote: Interrupt latency for character devices in Linux is 6-7 us, even with no other activity. You It has been a while but I ran tests on a system

Re: [chrony-users] GPS / Chrony NTP server config questions

Bill Unruh wrote: I am using chrony with serial PPS on a number of different machines, and I see the 6-7 us figure on HP Proliant systems while on Dell PowerEdge sytems it is more like 1us. No idea where the difference comes from. How do you measure that latency? It does seem that the

Re: [chrony-users] GPS / Chrony NTP server config questions

On Thu, 16 Nov 2017, Rob Janssen wrote: Bill Unruh wrote: On Thu, 16 Nov 2017, Denny Page wrote: Interrupt latency for character devices in Linux is 6-7 us, even with no other activity. You It has been a while but I ran tests on a system in which I changed the state of a parallel port

Re: [chrony-users] GPS / Chrony NTP server config questions

It has now been suggested to you at least by two different people-- hook your system up to the network, and do a timing using a nearby ntp server. That will give you of the order of 10-20us accuracy, and you can see if that time is the same as your pps time. I have no idea how accurate gpsd

Re: [chrony-users] GPS / Chrony NTP server config questions

On Thu, 16 Nov 2017, Denny Page wrote: Interrupt latency for character devices in Linux is 6-7 us, even with no other activity. You It has been a while but I ran tests on a system in which I changed the state of a parallel port pin and fed that into an interrupt grabbing the system time

Re: [chrony-users] GPS / Chrony NTP server config questions

I'm not too concerned about the accuracy of the PPS. This particular GPS receiver is pretty high quality. https://learn.adafruit.com/adafruit-ultimate-gps/overview It delivers the NMEA data and the PPS. A number of online resources describing similar projects and the GPSD Time Service HOWTO page

Re: [chrony-users] GPS / Chrony NTP server config questions

Interrupt latency for character devices in Linux is 6-7 us, even with no other activity. You can get better than this using a gpio and spinning on it, but I haven’t seen anyone do this with with serial pps. Denny > On Nov 16, 2017, at 09:57, Bill Unruh wrote: > > The

Re: [chrony-users] GPS / Chrony NTP server config questions

William G. Unruh __| Canadian Institute for| Tel: +1(604)822-3273 Physics _|___ Advanced Research _| Fax: +1(604)822-5324 UBC, Vancouver,BC _|_ Program in Cosmology | un...@physics.ubc.ca Canada V6T 1Z1 | and Gravity __|_ www.theory.physics.ubc.ca/ On Thu, 16 Nov 2017,

Re: [chrony-users] GPS / Chrony NTP server config questions

I'm trying to determine the best way to get an idea of my clock accuracy now that I'm getting the PPS signals. Is that "chronyc tracking"? When I do "chronyc sources" or "chronyc sourcestats" those seem to indicate NMEA offsets that are on the order of 40-60ms. debian@beaglebone:~$ chronyc

Re: [chrony-users] GPS / Chrony NTP server config questions

William G. Unruh __| Canadian Institute for| Tel: +1(604)822-3273 Physics _|___ Advanced Research _| Fax: +1(604)822-5324 UBC, Vancouver,BC _|_ Program in Cosmology | un...@physics.ubc.ca Canada V6T 1Z1 | and Gravity __|_ www.theory.physics.ubc.ca/ On Wed, 15 Nov 2017,

Re: [chrony-users] GPS / Chrony NTP server config questions

Thank you so much!! With the lock NMEA it is no longer ignoring the pulses. I should be able to make adjustments to the offset and whatnot to get the clock accuracy down to where I need it. On Wed, Nov 15, 2017 at 2:02 AM, Miroslav Lichvar wrote: > On Tue, Nov 14, 2017 at

Re: [chrony-users] GPS / Chrony NTP server config questions

On Tue, Nov 14, 2017 at 03:45:41PM -0500, Joe Smith wrote: > I rebuilt chrony with --enable-debug and ran with -d -d Below is some > output although I'm not 100% sure what it means. Tried looking at the > source code to see if I could ascertain the cause but I was unable. I let > it run for a bit

Re: [chrony-users] GPS / Chrony NTP server config questions

I have also not looked at the code recently but am suspicious. The time is for example 1510691647.698064095 That is almost exactly half way between the two seconds, and I think that the time needs to be within 1/4 sec of the top of the second for chrony to think that there is a lock, and to start

Re: [chrony-users] GPS / Chrony NTP server config questions

I rebuilt chrony with --enable-debug and ran with -d -d Below is some output although I'm not 100% sure what it means. Tried looking at the source code to see if I could ascertain the cause but I was unable. I let it run for a bit and here's some sample output. The pattern just seems to repeat

Re: [chrony-users] GPS / Chrony NTP server config questions

On Tue, Nov 14, 2017 at 07:40:33AM -0500, Joe Smith wrote: > Thank you for the quick response Bill... The PPS is coming in on /dev/pps1 > which is what I have in the refclock entry in my chrony.conf file. When run > the cat command corresponding to that device I get: > >

Re: [chrony-users] GPS / Chrony NTP server config questions

Thank you for the quick response Bill... The PPS is coming in on /dev/pps1 which is what I have in the refclock entry in my chrony.conf file. When run the cat command corresponding to that device I get: debian@beaglebone:~/ntp-gps-server/pps-overlay$ cat /sys/devices/virtual/pps/pps1/assert

Re: [chrony-users] GPS / Chrony NTP server config questions

On Mon, 13 Nov 2017, Joe Smith wrote: A little background... I am building a small NTP server utilizing a BeagleBone Black Rev C and an AdaFruit Ultimate GPS breakout board (with external antenna) (https://learn.adafruit.com/adafruit-ultimate-gps/overview). I have the hardware connected,