[ntp:questions] Fwd: Re: NetBSD GPS/PPS using 4.2.6p3

unruh unruh at wormhole.physics.ubc.ca
Fri Aug 26 14:23:55 UTC 2011

On 2011-08-26, Steve Kostecke <kostecke at ntp.org> wrote:
> On 2011-08-26, David J Taylor <david-taylor at blueyonder.co.uk> wrote:
>> "A C" <agcarver+ntp at acarver.net> wrote:
>>> I'll still have to put a serial monitor on the line and try to figure
>>> out what is being transmitted towards the GPS when the PPS driver is
>>> active.
>> I noticed that when updating from ntpd 4.2.7p97 to ntpd 4.2.7p206,
>> I noticed that the newer version is sending some RS-232 data to the
>> GPS soon after the PPS signal has started. I filed a bug report about
>> this:
>>   http://bugs.ntp.org/show_bug.cgi?id=1999
> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver20.html states:
> "The driver will send a $PMOTG,RMC,000*1D<cr><lf> comand each poll
> interval. This is not needed on most GPS receivers because they
> automatically send $GPRMC every second, but helps a Motorola GPS
> receiver that is otherwise silent. NMEA devices ignore commands they do
> not understand."

That should surely be a flag, not a default. To send out sentences by
default that you know most units do not understand is irresponsible.
There is not guarentee that all others devices will ignore it. It is
also an ugly kludge which in 20 years should have received a better
(And are there any Motorola devices that still behave that way?)

> Searching for "PMOTG", using the doc.ntp.org search facility, reveals that
> the same text is present on:
> http://doc.ntp.org/4.1.2/drivers/driver20.html
> http://doc.ntp.org/4.2.0/drivers/driver20.html
> http://doc.ntp.org/4.2.4/drivers/driver20.html
> http://doc.ntp.org/4.2.6/drivers/driver20.html
> http://doc.ntp.org/4.2.6p1/drivers/driver20.html
> http://doc.ntp.org/4.2.6p2/drivers/driver20.html
> http://doc.ntp.org/4.2.6p3/drivers/driver20.html
> So this is not a new addition to ntp-dev.

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