On Sat, 10 Nov 2012 15:23:21 -0000, David J Taylor wrote:
David,
Have you looked at the PPS line with a 'scope? No chance it's set to
something other than once-per-second, I suppose? In the first entry,
I wish I had a 'scope. It's probably high time I invest in one.
As for the 1PPS being something other than once-per-second, I was
operating under assumption that I would just natively be getting
once-per-second (or close to) from the Oncore receiver. I'm not sending
any additional commands to the receiver like Offset or cable delay prior
to starting up ntpd services; just using it as is defaultly.
it appears to assert at 12.0 and clear at 11.2. I don't understand
that! Any chance the level of the PPS signal is too low - is it TTL
and your receiver is expecting RS-232?
Just some thoughts...
That's a very good thought, indeed. I didn't think it was necessary to
convert the 1PPS signal to RS232 (-/+3 to -/+25) since the Motorola
engineering notes specifiy 0-+5v, that PPSAPI kernel logic would always
detect the rising edge from the 5v peak. Rethinking this a moment, I
guess logical 'OFF' with RS-232 is a negative range (-3 to -25), not
zero. Maybe it is the cause, because even the logical 'ON' isn't much
over over +3v.
I do have plenty of MAX232's sitting around, I could put that in front
of the 1PPS, then back into carrier detect pin and see what happens.
Then, what should I be looking for on that 'ppstest' output that would
tell me it's better or worse, aside from seeing that ntp would not
consider it a 'falseticker'?
-A
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