[time-nuts] NTP/1-PPS/RS232 question
"Björn"
bg at lysator.liu.se
Tue Aug 20 02:58:29 EDT 2013
>
> david-taylor at blueyonder.co.uk said:
>> Although, IIRC from discussions with Dave Hart, the Windows port can
>> only
>> accept the normal positive-going signal on the DCD line. The devices
>> I've
>> tested all have positive going signals. Pulse width is typically 100 or
>> 200
>> milliseconds, with a few receivers giving a much shorter pulse.
>
> Low cost GPS receivers usually have long PPS pulses. "Fancy" GPS
> receivers,
> like the TBolt or Z3801A have short pulses, ballpark of 10 microseconds.
> The
> short pulses sometimes don't get captured by the standard PPS software.
The PTTI 1PPS is defined in
http://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf
It is 20us long and common in some applications. However the voltage
levels are a bit high...
--
Björn
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