[ntp:questions] ntp version 4.2.7p257-o

unruh unruh at invalid.ca
Mon Feb 20 23:38:17 UTC 2012

On 2012-02-20, Dave Hart <hart at ntp.org> wrote:
> On Mon, Feb 20, 2012 at 17:34, unruh <unruh at invalid.ca> wrote:
>> On 2012-02-20, Dave Hart <hart at ntp.org> wrote:
>>> On Mon, Feb 20, 2012 at 04:53, Mark C. Stephens <marks at non-stop.com.au> wrote:
>>>> Why I say this is that that it's not related to the serial input as per:
>>>> C:\Documents and Settings\Administrator>ntpq -c clockvar
>>>> associd=0 status=0011 1 event, clk_no_reply,
>>>> device="NMEA GPS Clock", timecode="$GPZDA,044739,20,02,2012,+00,00",
>>>> poll=564, noreply=1, badformat=0, baddata=0, fudgetime2=-480.000,
>>>> stratum=0, refid=GPS, flags=1
>>>> the timecode looks great there, as does clockstats:
>>> It doesn't look great to me. ?I'd expect a checksum on the end of the
>>> sentence consisting of a * and two hex digits 0-9/A-F. ?I'm
>>> disappointed the Sure isn't generating the checksum, as is
>>> computationally trivial and serial transmission is far from inherently
>>> error-free. ?Earlier NMEA specification versions require the checksum
>>> only for $GPRMC, but the latest NMEA version mandates checksum on all
>>> sentences.
>> Lets not jump overboard to swim with assumptions. Sure DOES generate
>> checksums.
>> Here is from my Sure board
>> $GPGSV,4,3,14,19,16,316,18,27,07,083,17,29,06,156,,30,03,233,*7B
>> Now, ntpq -c clockvar may be stripping them off, but do not blame Sure
>> for that.
> We've seen thanks to David Taylor $GPGGA checksums and thanks to you a
> $GPGSV checksum, which are both encouraging.  I admit there's a
> possibility of truncation in the quoted timecode, but it wouldn't be
> due to ntpq in all likelihood, but ntpd and in particular
> http://bugs.ntp.org/2140.  However, the evidence is also consistent
> with the default Sure config not emitting a checksum with $GPZDA,
> though I sure hope it's not true.

Mine is the default. And it has a checksum.

> Cheers,
> Dave Hart

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