[ntp:questions] ntp version 4.2.7p257-o

unruh unruh at invalid.ca
Mon Feb 20 17:34:20 UTC 2012


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:
>>> I have not experienced the garbled characters. ?I was hoping your UART
>>> being overrun at high bps was the cause, but I'm sure it can manage
>>> 9600 cleanly. ?So I'm not positive the pending fixes will cure that aspect.
>>
>> Ah, I was aware that Hal had added some extra counters in the driver, and
>> I was thinking (novel concept there) that perhaps there is an error with the
>> new counters.
>
> Hal's new counters are for debugging purposes only, and are not yet
> integrated into ntp-dev, so they could not be the cause of your issue
> with p257.  When they are integrated, they will not affect operation
> other than exposing these debugging counters via ntpq -c clockvar.
>
>> 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. 

>
> Perhaps there's some way to enable checksum generation via a
> programming sentence from the PC.
>
> Cheers,
> Dave Hart



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