unruh wrote:
On 2011-08-24, David Lord <[email protected]> wrote:
A C wrote:
On 8/23/2011 15:27, unruh wrote:
On 2011-08-23, Uwe Klein<[email protected]> wrote:
unruh wrote:
But from his test, his system is labelling both edges.
so he has bounces on the line?
either that or rise/falltime is so low and noise so high
that receiver hysteris is not sufficient to supress multiple
HL/LH changes?
No, his test shows that the line changes and then 100ms later it changes
back and 900ms later it changes again (ie once per second it rises and
falls.) Ie, it is behaving exactly as it should if it were detecting a
pulse 100ms long.It is detecting both the rising and falling edge.
I just checked and the pulse is almost exactly 100 ms low going and 900
ms high (within about 1 ms) so it's 90% duty cycle high most of the time
with a swing low. The signal itself is clean down to microvolt levels.
The total voltage swing is about 12 volts (which would stand to reason
since I'm feeding the TTL level PPS output of the GPS board through one
channel of a MAX232 level shifter).
Therefore the machine is receiving a nice, clean PPS signal on DCD (DCD
pin was also verified yet again and is correct by hardware specifications).
You seem to be saying that the rs232 signal is low going,
ie low for 100ms then high for 900ms?
Previously I had the impression the pulse was high going
and you were using 'flag2 0'.
Ntpd requires the prefer peer to be within mindist before
even considering the PPS and then the system clock has to
be within a millisec of the PPS. Using one of your other
Are you sure? That seems a very verysilly requirement to put on the time
accuracy of the PPS. All that should be required is that the pulse be
within .5 sec of the "true time" in order to establish the "seconds" for
pps.
From my reading of the docs the ntp time has to be within
about 1 millisec of the pps before pps will sync.
A pps pulse within .5 sec of the "true time" doesn't make
any sense to me. Perhaps you meant the NMEA sentence used
needed to be within .5 sec but again that doesn't make a
lot of sense in practice as all three different gps units
I've used each have large variations in NMEA time so
require both fudge factor and increase in the range of
values that will be accepted.
David
sources as prefer peer and having NMEA disabled might give
you a better chance of getting the pps working without
having to bother about the time2 value.
David
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