[ale] NTP + GPS / with or without GPSD

[Michael H. Warfield]

On Tue, 2012-01-24 at 02:15 -0500, Ron Frazier wrote:
> As I've mentioned in other threads, I've been studying NTP and GPS and 
> computer timekeeping.  I have some GPS toys arriving in the mail soon, 
> and am looking forward to connecting it both to Windows and Linux for 
> timekeeping purposes.  I've read various accounts of using the GPS along 
> with NTPD.  I BELIEVE that NTPD can read the GPS on a serial TTY port 
> directly.

It can.

> And, as I understand it, a USB connected GPS appears as 
> though it's on a serial TTY port.

Most do.

> What I don't understand is the role 
> of GPSD.

GPSD is really used for two purposes depending on what you have and what
you need.

Probably the most important one is protocol translation.  I believe that
GPSD speaks a lot more GPS protocols, including some proprietary ones
from Delorme and, iirc, Magellan but those were older devices from many
many years ago.  I think they were using a Rockwell chipset back then.
GPSD spoke the Rockwell protocol and would emit NMEA down a socket to
slave applications, including NTPD.  All the modern Delorme units are
using pretty standard chip sets and modules that speak NMEA-1 or one of
its enhancements.  Not totally sure what NTPD speaks but, when I last
looked at this several years ago, it was pretty much NMEA.  If your GPS
is not supported but NTPD, you may need GPSD to do translations.

Second thing you use GPSD for is multiplexing applications and
distributing the GPS data to multiple clients.  You could have NTPD as a
client and GPSDrive as a client of the same data streams.

If you don't need either of those features, you don't need GPSD.

Mike

> I know I can run this in Linux, and that it works with NPTD to 
> set the system time.  However, I only have a port of NPT for Windows.  
> As far as I know, I cannot run GPSD in Windows, although I did read 
> something that said it would run in cygwin.  That sounds a little 
> kludgey.  So, what I need to know is if I can run my GPS time system 
> using ONLY NTP in Windows, without GPSD, because I know I can (and am) 
> running NTP on Windows.  (Aarg, acronym soup.)
> 
> If it helps, here's where I got my Windows version of NTP - 
> http://www.meinberg.de/english/sw/ntp.htm
> 
> As far as I know, it should be pretty much functionally the same as the 
> Linux version.
> 
> If anybody understands how this works, please advise.
> 
> Thanks in advance.
> 
> Sincerely,
> 
> Ron
> 
> -- 
> 
> (PS - If you email me and don't get a quick response, you might want to
> call on the phone.  I get about 300 emails per day from alternate energy
> mailing lists and such.  I don't always see new messages very quickly.)
> 
> Ron Frazier
> 
> 770-205-9422 (O)   Leave a message.
> linuxdude AT c3energy.com
> 
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-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
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