James Carlson <carls...@workingcode.com> wrote:
> > But I also mentioned that is is simple to write a driver that supports such
> > information. As Solaris does not support DCF-77 receivers, I did e.g. write
> > a
> > small driver that installs itself in the related callback tables from the
> > "zs"
> > driver in order to fetch the time when a related line from the DCF-77
> > receiver
> > indicated a second clock signal. This driver later allowed to read the time
> > stamp via ioctl.
>
> As long as your DCF-77 receiver has a PPS output, the system already
> supports it, and has supported it for ages. No special driver required.
>
> Look into the TIOCSPPS ioctl on the termio(7I) man page. Instead of
> relaying the information to user space (which involves latency), the
> mechanism automatically adjusts the system clock and latches the
> timestamp of the last tick. You can get the timestamp with TIOCGPPSEV.
>
> I'm pretty sure that xntpd supports this interface. I remember a
> co-working in Burlington setting up a test system with a GPS time source
> many years ago.
I did implement my code between 1992 and 1994 and the way I interpret the
documentation, it seems that the Solaris driver does not deal with the fact
that the pulse at the 59. second is missing.
DCF-77 uses cheap reaceiver hardware that has been developed by Telefunken for
Junghans wrist watches around 1980. For decoding the 0s and 1s in the data
stream, you set the baudrate to 50 baud and then use a char table to detect
100ms vs 200 ms pulses.
For DCF-77, you then need to throw away the pulse start time samples that are
outside the standard deviation and you need to implement a low pass on the
rest of the samples. If you do it the right way, you get aprox. 200 usec
accuracy when you have a user space daemon that implements the filters and
that sets an adjust value for adjtime().
Is this implemented on Solaris now?
Jörg
--
EMail:jo...@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
j...@cs.tu-berlin.de (uni)
joerg.schill...@fokus.fraunhofer.de (work) Blog:
http://schily.blogspot.com/
URL: http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily
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