[ntp:questions] Ramifications of bug 1999 resolution: "Remove PMOTG output senten ce from Type-20 driver"

Long, Darren Darren.Long at uk.thalesgroup.com
Fri Sep 30 12:39:05 UTC 2011

Hi all,

I've just noticed bug 1999, "Remove PMOTG output sentence from Type-20

I've found a use for the PMOTG message output, which I've started to use as
a heartbeat from ntpd in my bespoke nav software which forwards RMC messages
to the ntpd via a virtual serial port on Windows. I find this to be a useful
mechanism to determine if the panic threshold has been exceeded and ntpd has
aborted, as my software can generate an alert to the user that they should
set the system clock to UTC, at least within the tolerance of the panic

Whilst I agree that ntpd probably doesn't need to send this by default, and
also have no imminent concern as we're using the new stable release 4.2.6p4
which still sends the PMOTG messages at the poll interval, I'd like to know
that ntpd can still be built with this mechanism enabled for refclock 20 in
future versions.

I note that NMEA_WRITE_SUPPORT is defined in refclock_nmea.c and wonder if
instead of the option being buried there, it could instead be enabled more
conveniently (for Windows ports and regular builds) at build time without
resorting to patching code.

I also appreciate that this is a real corner case and that I'm a little fish
in a big pond, so I could understand if there was no desire to accomodate my
needs, but it would be good to know what the future holds in this regard
before I pack and ship my nav sw.

Darren Long

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