[LinuxPPS] gps_nmea error

[Hal V. Engel]

On Tuesday 12 August 2008 11:21:44 am Udo van den Heuvel wrote:
> Ritter, Nicholas wrote:
> > I unloaded the pps related modules and reloaded them and noticed that
> > the kernel does not see any PPS pulse unless the ktimer module is
> > loaded, us this the way it should be?
>
> ktimer is fake PPS.
> do the ppsldisc thingie and see /dev/pps0 appear
>
> > Thanks Udo for the config example. I have confirmed that my GPS unit is
> > set to 200ms.
>
> 'works for me', not  the end-all answer.

I think the real answer is that the PPS pulse needs to be at least as long as 
the kernal timer interval.  So it you have your kernel setup for 100 ticks per 
second the PPS pulse needs to be at least 10 milliseconds.  So you were likely 
OK when you had this set to 30ms.  Some of these refclocks put out very short 
PPS pulses that are less than a millisecond and for these devices you need to 
have a conditioning circuit that outputs a longer pulse.  This is not an issue 
with your device.

Hal
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