Re: [Linuxptp-devel] gpsd support in ts2phc
On Fri, May 14, 2021 at 7:33 PM Richard Cochran wrote: > > On Thu, May 13, 2021 at 07:31:27PM +0200, Lars Munch wrote: > > On Sat, May 8, 2021 at 8:47 PM Richard Cochran > > wrote: > > > > > > On Sat, May 08, 2021 at 02:57:30PM +0200, Lars Munch wrote: > > > > > > > 1. Use the time provided by gpsd to ntpshm. This can be implemented > > > > without > > > > dependencies to gpsd. > > > > > > Doesn't sound aweful, but not great either. > > > > I kind of like the simplicity of this solution. No need for extra > > daemons to pipe the > > data from gpsd to ts2phc. The thing I do not like is the polling that > > it would have to > > do, but that's only a few times per second. Anything else that I have > > missed which > > is awful? > > > > Does this mean I should not waste my time implementing this as you can > > already > > now say it will not be accepted? > > There are two design questions that need answering. > > 1. Will this work reliably? That is, will the ntpshm (almost) always >have correct time? Or will this become a constant source of >questions on the list to the tune of, "I used linuxptp as a GPS GM >and it does not work ..." I do NOT want to become a support >channel for gpsd. > > 2. How can the GM logic determine whether the time in the ntpshm is >verified to be globally correct or not? > > With the present solution using RMC, we have a simple flag (field 2 is > either "A" or "V") that signals the validity. It is practically > impossible to determine generically whether the reading from a > particular GNSS radio is valid. For this reason we push the > responsibility to an external program. Thank you for taking the time to share your thoughts on the subject. I will write an external program instead as the gpspipe | socat solution is too flaky. Regards Lars ___ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
Re: [Linuxptp-devel] gpsd support in ts2phc
On Thu, May 13, 2021 at 07:31:27PM +0200, Lars Munch wrote: > On Sat, May 8, 2021 at 8:47 PM Richard Cochran > wrote: > > > > On Sat, May 08, 2021 at 02:57:30PM +0200, Lars Munch wrote: > > > > > 1. Use the time provided by gpsd to ntpshm. This can be implemented > > > without > > > dependencies to gpsd. > > > > Doesn't sound aweful, but not great either. > > I kind of like the simplicity of this solution. No need for extra > daemons to pipe the > data from gpsd to ts2phc. The thing I do not like is the polling that > it would have to > do, but that's only a few times per second. Anything else that I have > missed which > is awful? > > Does this mean I should not waste my time implementing this as you can already > now say it will not be accepted? There are two design questions that need answering. 1. Will this work reliably? That is, will the ntpshm (almost) always have correct time? Or will this become a constant source of questions on the list to the tune of, "I used linuxptp as a GPS GM and it does not work ..." I do NOT want to become a support channel for gpsd. 2. How can the GM logic determine whether the time in the ntpshm is verified to be globally correct or not? With the present solution using RMC, we have a simple flag (field 2 is either "A" or "V") that signals the validity. It is practically impossible to determine generically whether the reading from a particular GNSS radio is valid. For this reason we push the responsibility to an external program. Thanks, Richard ___ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
Re: [Linuxptp-devel] gpsd support in ts2phc
On Sat, May 8, 2021 at 8:47 PM Richard Cochran wrote: > > On Sat, May 08, 2021 at 02:57:30PM +0200, Lars Munch wrote: > > > 1. Use the time provided by gpsd to ntpshm. This can be implemented without > > dependencies to gpsd. > > Doesn't sound aweful, but not great either. I kind of like the simplicity of this solution. No need for extra daemons to pipe the data from gpsd to ts2phc. The thing I do not like is the polling that it would have to do, but that's only a few times per second. Anything else that I have missed which is awful? Does this mean I should not waste my time implementing this as you can already now say it will not be accepted? > > I might also be able to use gpspipe and socat to get the NMEA sentences > > from gpsd to ts2phc, but that is not very elegant. > > This is best approach IMO. You can wrap gpspipe|socat in a systemd > job to get automatic restarting and logging and so on. If the > gpspipe|socat combination is too flaky to keep running, then writing a > little C or python program to read the UART and publish two sockets is > pretty easy. For the email archives; the following works as long as you do no restart anything: $ gpspipe -r | socat -u STDIN TCP4-LISTEN:9876,reuseaddr,fork,bind=127.0.0.1 and then configured ts2phc.nmea_remote_host, ts2phc.nmea_remote_port. Thanks Lars Munch ___ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
Re: [Linuxptp-devel] gpsd support in ts2phc
On Sat, May 08, 2021 at 02:57:30PM +0200, Lars Munch wrote: > 1. Use the time provided by gpsd to ntpshm. This can be implemented without > dependencies to gpsd. Doesn't sound aweful, but not great either. > 2. Use libgpsd to get the time, but that adds a dependency to gpsd No, I won't use that library in linuxptp. Before implementing the current solution in nmea.c, I tried really hard to use gpsd, hoping that it would "just work" because of the multiple different nmea and binary protocols that it has. That seemed like a compelling feature. However, I couldn't get it to work with either a commodity gps or a high end, survey quality gps. > I might also be able to use gpspipe and socat to get the NMEA sentences > from gpsd to ts2phc, but that is not very elegant. This is best approach IMO. You can wrap gpspipe|socat in a systemd job to get automatic restarting and logging and so on. If the gpspipe|socat combination is too flaky to keep running, then writing a little C or python program to read the UART and publish two sockets is pretty easy. Thanks, Richard ___ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
Re: [Linuxptp-devel] gpsd support in ts2phc
My experiences of gpsd are not good. It didn’t (three years ago) have recovery in case it got out of sync with NMEA messages. When it stopped working, you had to kill it and restart From: Lars Munch [mailto:l...@segv.dk] Sent: Samstag, 8. Mai 2021 13:58 To: linuxptp-devel@lists.sourceforge.net Subject: [Linuxptp-devel] gpsd support in ts2phc Hi I have been using ts2phc directly to my GPS using serial connection to get NMEA sentences. This is working fine but then I cannot get status from the GPS while ts2phc is running. Therefore I have been pondering on how to add gpsd support to ts2phc. There are several options, maybe more: 1. Use the time provided by gpsd to ntpshm. This can be implemented without dependencies to gpsd. 2. Use libgpsd to get the time, but that adds a dependency to gpsd I might also be able to use gpspipe and socat to get the NMEA sentences from gpsd to ts2phc, but that is not very elegant. Any suggestions? Thanks Lars ___ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
[Linuxptp-devel] gpsd support in ts2phc
Hi I have been using ts2phc directly to my GPS using serial connection to get NMEA sentences. This is working fine but then I cannot get status from the GPS while ts2phc is running. Therefore I have been pondering on how to add gpsd support to ts2phc. There are several options, maybe more: 1. Use the time provided by gpsd to ntpshm. This can be implemented without dependencies to gpsd. 2. Use libgpsd to get the time, but that adds a dependency to gpsd I might also be able to use gpspipe and socat to get the NMEA sentences from gpsd to ts2phc, but that is not very elegant. Any suggestions? Thanks Lars ___ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
