[Thumbgps-devel] "Plain Jane" timing GPS is working!

[Dave Hart]

On Tue, Apr 3, 2012 at 14:59, Ron Frazier (NTP)
<timekeepingntplist at techstarship.com> wrote:
> I had my Sure board working a couple of weeks ago connected SERIAL ->
> Prolific adapter -> USB, with PPS patched to DCD, running NTPD on Windows
> using Dave Hart's new binaries, without running GPSD.  It was working fine
> within + / - 1 ms of GPS time.  It was definitely reacting to the pulses.
>  Maybe you could try with NTPD only.  I was using the "20" NMEA driver with
> the PPS flag 1 active.  I don't know for sure if the Linux version of NTPD
> has all the features necessary to do this.

The Windows port of ntpd is the only one which has the crude user-mode
PPS hack needed to use PPS without PPSAPI.  On Linux, gpsd is the way
to achieve the same.  Incidentally that user-mode PPS hack will be
moving from ntpd's Windows serial I/O layer to a separate PPSAPI
provider DLL before long, so that it will be disabled by default and
enabled only when desirable by administrator action.  It will also
behave better via PPSAPI, so that for example NMEA's fudge time1 is
used to offset PPS timestamps as designed, rather than fudge time2
(which is intended to control only NMEA timestamps, but the user-mode
PPS hack substitutes the first NMEA timestamp each cycle with the PPS
timestamp.  Also currently the fact that PPS is used is invisible, but
when it's done with a PPSAPI provider DLL, ntpd will show the 'o'
tally code for the PPS-enabled refclock rather than '*'.

Cheers,
Dave Hart