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

[Hal V. Engel]

On Tuesday 21 July 2009 06:21:12 pm K. Connolly wrote:
> 2. Here is an example of what my ppstest results look like.
> # ./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 0.000000000, sequence: 0 - clear  1248162516.998840147,
> sequence: 21
> source 0 - assert 0.000000000, sequence: 0 - clear  1248162517.998967408,
> sequence: 22

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