On 8/23/2011 06:02, Thomas Laus wrote:
On 2011-08-22, A C<[email protected]> wrote:
Yes but ntpd still doesn't see the PPS signal on DCD with or without
flag3. So I'm lost on how to solve this problem. I know the PPS signal
is there on the wire, I know DCD is being asserted and cleared. I know
the test code can see it but for some reason I just can't make ntpd see it.
Does your PPS signal stay at logic 0 for most of the time and go to
logic 1 for a short time? Does the PPS signal stay at logic 1 level
for most of the time and then go to logic 0 for a short time? You
will require either an analog voltmeter or oscilloscope to read this
data. Some GPS receivers generate a very short pulse and require
intervening hardware to stretch the pulse width to something the PC
can read reliably. The capture / assert configuration options does
not select reading the leading or trailing edge of a PPS pulse, NTP
only reads timestamps to the on the leading edge and you may require
an inverter to swap polatity for NetBSD to read and sync to your PPS
pulse.
The duty cycle is about 10% (100ms on 900ms off). I'll try tossing in
the pulse stretcher and/or inverter just after the GPS receiver and see
what happens.
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