[ntp:questions] problem with ntpd refclock and pps via parallel port

David Lord snews at lordynet.org
Sun Jan 31 23:37:01 UTC 2010

problem with ntpd refclock and  pps via parallel port


on system A I had type 22 pps working ok from pps at ttl
level to DCD of serial port. This was a bit erratic and
temperature sensitive possibly due to mismatch of ttl/rs232

on system B, rather than add complication of ttl=>rs232
conversion I've connected pps to parallel port and changed
symlink to be /dev/pps0 => /dev/lpt0

With same NetBSD-5-PPS kernel as on system A, I am getting following in 
ntp.log at startup:
   refclock_atom: /dev/pps0: Interrupted system call
   configuration of failed
No PPS shown by 'ntpq -p'

A google for above here gave some messages from suggesting
use of atppc* at isa?, ppbus* at atppc?, pps* at pps?
so now I have dmesg with
    atppc0 at isa0 ......
    atppc0: capabilities=3<INTR,DMA>
    ppbus0 at atppc0
    lpt0 at ppbus0
    pps0 at ppbus0

System B, NetBSD-5, doesn't have a refclock, just other
ntp servers but ntp docs appear to state this as being ok.

On system C, NetBSD-4.0.1, which is working ntp server with
MSF clock on serial via DCD, I've just tried link
pps0 => lpt0 and have same output from ntpd as from system B.
I've since rewired system C with MSF to serial dsr and
pps to serial dcd, restarted and ntpq shows
SHM(0)/MSFa and PPS(0) and after a short while get +SHM(0)
then oPPS(0) with system having drifted > 10ms whilst
rewiring and restarting but now back at < 1ms.

So does pps really need a refclock and/or does pps via
parallel work ok or not on NetBSD-5?

Tomorrow I'll rewire gps that just about works ok out of
bedroom window and give that a try on system A, NetBSD-5,
with both serial and parallel.



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