====== LinuxPPS wiki ======

Welcome to new LinuxPPS's wiki page!

===== Overview =====

LinuxPPS provides a programming interface (API) to define in the
system several PPS sources.

PPS means "pulse per second" and a PPS source is just a device which
provides a high precision signal each second so that an application
can use it to adjust system clock time.

A PPS source can be connected to a serial port (usually to the Data
Carrier Detect pin) or to a parallel port (ACK-pin) or to a special
CPU's GPIOs (this is the common case in embedded systems) but in each
case when a new pulse arrives the system must apply to it a timestamp
and record it for userland.

Common use is the combination of the NTPD as userland program, with a
GPS receiver as PPS source, to obtain a wallclock-time with
sub-millisecond synchronisation to UTC.

More detailed information regarding PPS and LinuxPPS are available at [[Technical information]] page.

===== Resources =====

A LinuxPPS's mail list is available at [[http://www.linuxpps.org/cgi-bin/mailman/listinfo/discussions]] where you can send to your LinuxPPS related questions (please avoid asking about userland problems nor ''ntpd'' or ''chrony'' servers, etc.).

However **before** sending your questions to this list, please, **take a look** to the [[LinuxPPS FAQ]] page!

===== LinuxPPS based projects =====

Projects using LinuxPPS:

  * Dedicated Short Range Communications (DSRC) radio synchronization used by US-DOT's VII [[http://www.its.dot.gov/vii/]] [[http://en.wikipedia.org/wiki/Vehicle_infrastructure_integration]].

  * [[http://www.mmarray.org/|Owens Valley Radio Observatory]] (OVRO / CARMA) correlator system.

  * [[http://ntpi.openchaos.org/pps_pi/|Raspberry Pi Stratum 1 NTP server with PPS]]. Accurate timekeeping at low cost.

  * [[https://github.com/rascol/PPS-Client|PPS-Client daemon for Raspberry Pi 2, 3 or 4 B or B+ or an AMD/Intel desktop system]]. Accurate time keeping precision of a timeline with a standard deviation of 0.5 microsecond and a typical time keeping accuracy of 2 microseconds.

If you have a project that is using LinuxPPS and you would like it to be shown here, please email [[giometti@ennenne.com]].

===== Press =====

Press talked about the LinuxPPS project on:

  * Linux&C. issue 68 (year 11) at page 5 (Italian magazine).

  * Linux Journal issue 185 (September 2009) at page 14. 

===== Contributors =====

==== PayPal ====

  * Kenji Hiranuma

  * [[http://www.vanheusden.com/|Folkert van Heusden]]

Other contributions can be done via [[http://paypal.me/RodolfoGiometti|PayPal]].

==== Hardware ====

  * [[http://www.meinberg.de/english/products/lantime-m200-gps.htm|LANTIME M200/GPS]] from [[http://www.meinberg.de/Meinberg | Meinberg]].

==== Misc ====

[[https://www.meinbergglobal.com/|{{:meinberg_logo.png?nolink&100 | Meinberg}}]]

  * Many thanks to [[https://www.meinbergglobal.com/|Meinberg]] for donating this new WEB space.

  * Thanks to [[andreas.puls@meinberg.de|Andreas Puls]] for the LinuxPPS's logo.

  * Thanks to [[http://www.worldtimesolutions.com/|World Time Solution]] for asking to me to do some improvements on LinuxPPS code.