# PPS on serial port

**URL:** <https://community.ntppool.org/t/pps-on-serial-port/1039>\
**Category:** Client Configuration and Development\
**Created:** [January 8, 2019, 6:12pm UTC](https://community.ntppool.org/t/pps-on-serial-port/1039 "2019-01-08T18:12:12Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![W9GYR](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/w9gyr/32/276_2.png) [@W9GYR](https://community.ntppool.org/u/W9GYR)\
**Post date:** [January 8, 2019, 6:12pm UTC](https://community.ntppool.org/t/pps-on-serial-port/1039/1 "2019-01-08T18:12:13Z")

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I’ve been running a GPS with NMEA and PPS outputs connected to a server with a DB25 serial port. The PPS is wired to the DCD pin with the type 20 generic NMEA driver. The new server that I would like to connect the GPS to has a Cisco/Sun type RJ-45 serial port that lacks the modem control pins. I can’t find any documentation that mentions using DSR for the PPS. Is there a reference clock driver that will recognize the PPS on a flow control pin?

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**Author:** ![littlejason99](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/littlejason99/32/242_2.png) [@littlejason99](https://community.ntppool.org/u/littlejason99)\
**Post date:** [January 8, 2019, 8:35pm UTC](https://community.ntppool.org/t/pps-on-serial-port/1039/2 "2019-01-08T20:35:25Z")

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What OS?

If you are using linux you can use GPSD which I believe supports PPS on alternate pins. Then you use a SHM refclock with NTP to talk to GPSD.

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**Author:** ![jailbird](https://avatars.discourse-cdn.com/v4/letter/j/7ab992/32.png) [@jailbird](https://community.ntppool.org/u/jailbird)\
**Post date:** [January 9, 2019, 8:25am UTC](https://community.ntppool.org/t/pps-on-serial-port/1039/3 "2019-01-09T08:25:50Z")

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Nothing to do with gpsd, as PPS handling it done at the kernel level.

I personally just ended up buying a cheap PCIe serial (or parallel!) card from Amazon and using that.

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**Author:** ![W9GYR](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/w9gyr/32/276_2.png) [@W9GYR](https://community.ntppool.org/u/W9GYR)\
**Post date:** [January 20, 2019, 2:47am UTC](https://community.ntppool.org/t/pps-on-serial-port/1039/4 "2019-01-20T02:47:25Z")

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This is a Sun/Oracle server running Solaris.

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**Author:** ![littlejason99](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/littlejason99/32/242_2.png) [@littlejason99](https://community.ntppool.org/u/littlejason99)\
**Post date:** [January 20, 2019, 5:41pm UTC](https://community.ntppool.org/t/pps-on-serial-port/1039/5 "2019-01-20T17:41:16Z")

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I did a little digging around and @jailbird is right, this is implemented in the kernel (timepps.h which is used by NTP merely interfaces with it).

I would have to agree, easiest route without making a ton of headaches for yourself would be to simply drop in a serial port card that has a chip solaris supports and connect to the DCD pin.

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**Author:** ![W9GYR](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/w9gyr/32/276_2.png) [@W9GYR](https://community.ntppool.org/u/W9GYR)\
**Post date:** [January 22, 2019, 4:54pm UTC](https://community.ntppool.org/t/pps-on-serial-port/1039/6 "2019-01-22T16:54:04Z")

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Thanks for the info. I’ll take a look at adding serial hardware.