Hi,
I want to sync my arm host clock with a GPS clock using your package gpsd but we have some differences in the configuration.
Typical implementations of that synchronization use your package gpsd to read NMEA messages through serial and get the absolute time. This absolute time together with a PPS signal is used to sync the clocks with chrony or ntpd.
In my case, I have a Piksi Multi RTK GNSS module https://www.swiftnav.com/piksi-multi that I am using in Linux 18.04 with ROS. This device is manufactured by Swift Navigation and they have their own protocol called SBP (Swift Navigation Binary Protocol) instead of using NMEA. The module also provides a PPS signal. We have a Nvidia Jetson Xavier as a host Arm computer. We connect the GPS with the Nvidia through ethernet.
We have a way to extract the absolute time of the SBO message using a ROS (Robotics Operating System) wrapper of the Piksi GPS https://github.com/ethz-asl/ethz_piksi_ros. ROS is basically a robotics middleware that runs on Linux. My question is if I could use this absolute time from ROS in the gpsd pkg rather than from the serial NMEA msg in order to sync my clocks.
Thanks so much in advance. It would mean a lot if you could help me with this. If you need any more information on the configuration or device, please let me know.
Best,
On Thu, Feb 25, 2021 at 5:07 PM Gary E. Miller <gem@rellim.com> wrote:
Yo Xavier!
gpsd support by private email is for paying customers only:
https://gpsd.io/SUPPORT.html#_development_mailinglist
Please redirect future correspondence to the gpsd-user@nongnu.org
mailing list, unless you prefer to send a checn.
More inline below.
On Thu, 25 Feb 2021 15:54:16 +0100
Xavier Ruiz <xavier.ruiz@earthrover.farm> wrote:
> Hi Gary and Eric,
>
> I am trying to sync my host computer against a PPS signal provided by
> a GPS and I came across your website:
> https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html. I would be
> very grateful if you could take a minute to answer a question I have.
> It would help me a lot.
Glad it helped.
> My question is: can gpsd be used with a GPS connected through ethernet
> communicating through tcp rather than serial?
Yes, this is briefly documented on the gpsd man page.
> We have a Piski Multi
> RTK GPS that is configured that way and we use SBP messages (swift
> navigation binary protocol) rather than NMEA.
I've never heard of Pitski, Swift or SBP. Do you have documentation
on the protocol?
> We are also using ROS
> so we have a GPS msg stamped with the real GPS time. Is there a way
> to use this time in the gpsd rather than the one obtained through
> serial from an NMEA msg?
ROS is just another Linux distro, but you do not say how it is
configured. I don't know what you mean by "real GPS time". In GPS
land the speed of light, and special relativety apply, so "real" is
imaginary.
Follow-ups to the list please.
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
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