[LinuxPPS] 1PPS Atom Ref Clock Not being Polled?

[K. Connolly]

On Wed, 22 Jul 2009, Hal V. Engel wrote:

> This looks really strange to me.  It appears that your machine is seeing the
> clear events but NOT the assert events.

Well, I had a vague memory of the ppstest results looking good, so after 
toying with unloading and reloading all the serial/pps-related modules and 
noticing different results, I decided to reboot the system. Whatever that 
did, it fixed things. Now I consistently get a "nice" looking ppstest 
result, with a clear and assert sequence (Note, however, that the LinuxPPS 
wiki only shows an assert event... Whereas I have both, clear and 
assert?):

# ./ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1248328039.918108480, sequence: 14217 - clear 
1248328039.918140245, sequence: 14225
source 0 - assert 1248328040.918084706, sequence: 14218 - clear 
1248328040.918109885, sequence: 14226
source 0 - assert 1248328041.918062542, sequence: 14219 - clear 
1248328041.918093635, sequence: 14227
source 0 - assert 1248328042.918037012, sequence: 14220 - clear 
1248328042.918063567, sequence: 14228
source 0 - assert 1248328043.918015496, sequence: 14221 - clear 
1248328043.918045888, sequence: 14229
source 0 - assert 1248328044.917992022, sequence: 14222 - clear 
1248328044.918016521, sequence: 14230


Despite this promising result, the behavior of my NTPd is still the same, 
and the PPS device is not being polled. And, for what it's worth, I tried 
switching the rising edge detection to falling edge, to no avail. UHG.

-Kevin


   Could this be because of the short
> length of the PPS pulse?  From my reading for this to be reliable the pulse
> length has to be at least = 1/Hz rate of the kernel (IE. 100ms on a 100Hz
> system or 10ms on a 1000Hz system).  But I don't know for sure that this is
> really true but in any case your pulse is 20us (0.02ms) and this is way
> faster.  So this is at least suspect.
>
> Also
>
>> server 127.127.22.0 minpoll 4 maxpoll 4
>> fudge 127.127.22.0 flag3 1 flag2 0 time1 0.000 stratum 0
>
> You are telling ntp to use the assert edge (flag2 0) and since you are not
> seeing the assert when you run ppstest I think this is why ntp is failing
> since it never see an assert.  As a test try using the clear edge (flag2 1).
> If that works then you know that the problem is that the machine is not seeing
> the assert events.
>
> Hal
>
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