[ntp:questions] ntpd connect gpsd shared memory driver

Charles Elliott elliott.ch at verizon.net
Wed Jun 19 09:48:52 UTC 2013


> When you want to use the receiver both for
> time sync and position info, the data somehow has to be multiplexed.

While this does not help the present problem, it may be possible to
multiplex GPS device output under Windows and using a SiRF receiver.  The
new SiRF demo program (Version 3.87) says it can read a SiRF receiver using
SiRF's proprietary protocol binary output, and the demo program will output
corresponding NMEA ASCII messages to a virtual COM port.  If that works, and
I have not tried it, one could see position, time, and a satellite map in
the demo program and NTPS could still receive the NMEA messages.

One can find SiRFDemo (3.87) by searching for it with Google or Bing.

Charles Elliott

> -----Original Message-----
> From: questions-bounces+elliott.ch=verizon.net at lists.ntp.org
> [mailto:questions-bounces+elliott.ch=verizon.net at lists.ntp.org] On
> Behalf Of Rob
> Sent: Tuesday, June 18, 2013 4:47 PM
> To: questions at lists.ntp.org
> Subject: Re: [ntp:questions] ntpd connect gpsd shared memory driver
> 
> Richard Cagley <rcagley at gmail.com> wrote:
> > Does "removing a definition" refer to removing one of the timeservers
> from
> > the ntp.conf file? Presently, I don't have pps support built into my
> kernel.
> 
> I'm sorry, but I am not familiar with it.
> I use gpsd+ntpd on a system without pps support.
> 
> I think it can be done in two ways (but I am not sure):
> 1. by using a driver inside ntpd to support a GPS receiver
> 
> 2. by using some program to tell the kernel where to look for pps
> pulses.
> 
> That program is then probably called somewhere in system startup.
> But I don't have any details on that.
> 
> What should be clear is that you *cannot* use the ntpd driver for a
> GPS receiver and gpsd at the same time.  They would have to share the
> data from the serial port.
> 
> In fact this is one of the reasons why gpsd exists at all, and why it
> has time sync functions.   When you want to use the receiver both for
> time sync and position info, the data somehow has to be multiplexed.
> 
> (it seems there is some limited function in one of the ntpd GPS drivers
> to save the position info somewhere where it can be accessed by other
> programs)
> 
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