[ntp:questions] Re: Errors with NMEA refclock

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Mon Jan 30 17:48:43 UTC 2006


Terje Mathisen wrote:
> Harlan Stenn wrote:
>
>>>>> In article <43DD34D3.8000600 at ntp.isc.org>, mayer at ntp.isc.org
>>>>> (Danny Mayer) writes:
>>
>>
>> Niall> as far as I can tell only 4800 is supported with the default
>> driver
>>
>> Danny> If there's something wrong with the baud rates lets get it
>> fixed. We Danny> just have to know what's wrong.
>>
>> There's a reason it's set to 4800.  I don't know what the reason is,
>> but there is a reason.
>
> A very good reason indeed:
>
> 4800 baud is an intrinsic part of the NMEA spec! :-)
>
> All devices that talk NMEA do so at 4800.
>
> Terje

You are, of course, correct.  However, many devices /do/ allow higher 
speeds (which would provide lower timekeeping jitter), but there is no 
easy way to tell ntpd about the higher speed.  I see that flag1 and flag4 
are unused for this driver, so that might be a way to pass the port number 
and baud rate under Windows.  E.g. flag4 19200.

(Perhaps the port number is implied already by the unit number in the 
address?)

David 





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