[LinuxPPS] parallel port pps info

[Remco den Besten]

Hi Steve,

I tried multiple PPS inputs, also in conjcuntion with 'your' shmpps.
Indeed, I also experienced some 'interference' between shmpps and LinuxPPS.

When using LinuxPPS only, I remember that ntpd takes the 'first' and not 
'the best' PPS.
Do not remember whether this was the 'GPS-PPS' or another one.
It was a while ago and I wait until the new ppsldisc discussions settle.

Anyway, I could not get shmpps to work on the parallel port, but that is out 
of scope
of this mailinglist.

> And the /dev/pps1 entry also shows up. This fed a pps signal ok,
> except that it seemed to override the GPS pps signal, so I unloaded
> the lp module and replaced it with the ppsdev module so I could
> run the userspace shm pps program.
>
> The shm program worked fine, however it seemed to perturb the linuxpps
> badly. The offset shown in the shm program became the offset shown
> by ntpd. This is very confusing, I had not configured a shm driver
> in ntpd, and I had unloaded the lp module, so I can't even imagine
> how the ntpd could be affected. Even after I stopped the shm
> program the offset seemed to still be tweaked by the parallel port
> input. Only after i *physically disconneced* the cable does the
> GPS pps signal take over again
>
> It feels like I've really Lost It (cough, american slang for
> flipping out, losing your marbles, few cards short of a full deck,
> etc etc).

Remco