# Serial GPS Sync help **URL:** \ **Category:** Uncategorized\ **Created:** [February 11, 2021, 1:54pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911 "2021-02-11T13:54:16Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![MaxandreOgeret](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/maxandreogeret/32/701_2.png) [@MaxandreOgeret](https://community.ntppool.org/u/MaxandreOgeret)\ **Post date:** [February 11, 2021, 1:54pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/1 "2021-02-11T13:54:16Z")
Hello, I have a GPS and I would like to synchronize with it. The GPS has 3 wired going out : - PPS - NMEA over UART - Ground I believe I will need to make a RS232 cable and plug it in the back of the computer but what is the pinout exactly ? I have found this for a Garmin GPS but would it be similar ? ![image](https://us1.discourse-cdn.com/flex016/uploads/ntppool/original/1X/1ae41b3201c3b7315b69cd88807bba72258d8765.png) And later how do I make use of this data to sync the clock with it ? Thanks for your help ! ---
**Author:** ![alica](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/alica/32/337_2.png) [@alica](https://community.ntppool.org/u/alica)\ **Post date:** [February 11, 2021, 2:54pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/2 "2021-02-11T14:54:49Z")
Normal GPS devices using serial connection should have at least a pair of Tx/Rx and a power circuit (+5V/power ground in your Garmin image) to make it work, 4 pins in total. So if your device has only 3 wires then it may be not using generic serial connection. You may need to check its manual for more wiring and connecting instructions… ---
**Author:** ![elljay](https://avatars.discourse-cdn.com/v4/letter/e/5fc32e/32.png) [@elljay](https://community.ntppool.org/u/elljay)\ **Post date:** [February 11, 2021, 3:32pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/3 "2021-02-11T15:32:06Z")
Hi, what is the make and model of GPS you have? [This](http://www.rjsystems.nl/en/2100-ntpd-garmin-gps-18-lvc-gpsd.php) is a good guide for Garmin GPS 18 LVC with a serial connection. ---
**Author:** ![MaxandreOgeret](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/maxandreogeret/32/701_2.png) [@MaxandreOgeret](https://community.ntppool.org/u/MaxandreOgeret)\ **Post date:** [February 11, 2021, 3:54pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/4 "2021-02-11T15:54:34Z")
I have a Novatel Pwrpak7. Why would I need the wire going back to the GPS if I never send anything to it ? ---
**Author:** ![elljay](https://avatars.discourse-cdn.com/v4/letter/e/5fc32e/32.png) [@elljay](https://community.ntppool.org/u/elljay)\ **Post date:** [February 11, 2021, 4:02pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/5 "2021-02-11T16:02:06Z")
Looks very nice! [This page](https://docs.novatel.com/OEM7/Content/Technical_Specs_Receiver/PwrPak7_Connectors.htm?TocPath=Specifications%7CPwrPak7%20Technical%20Specifications%7C _____ 8) has pinouts assuming I’ve found the right model… ---
**Author:** ![MaxandreOgeret](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/maxandreogeret/32/701_2.png) [@MaxandreOgeret](https://community.ntppool.org/u/MaxandreOgeret)\ **Post date:** [February 11, 2021, 4:04pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/6 "2021-02-11T16:04:52Z")
Indeed it is ! Yes it is the right model, and I have the NMEA UART and PPS configured. What software do you recommend once it’s connected with a serial cable to the computer ? ---
**Author:** ![elljay](https://avatars.discourse-cdn.com/v4/letter/e/5fc32e/32.png) [@elljay](https://community.ntppool.org/u/elljay)\ **Post date:** [February 11, 2021, 4:08pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/7 "2021-02-11T16:08:46Z")
If you’re running some flavour of Linux I’d suggest the tried and tested GPSD - [this](http://www.rjsystems.nl/en/2100-ntpd-garmin-gps-18-lvc-gpsd.php) is a good guide. ---
**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:** [February 18, 2021, 3:37pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/8 "2021-02-18T15:37:29Z")
> [@MaxandreOgeret](#): > > Why would I need the wire going back to the GPS if I never send anything to it ? Most GPS units accept various commands, like to change the port settings, or which strings to output, soft reset, upload/download the almanac, set a static location, start survey mode, etc, etc… ---
**Author:** ![MaxandreOgeret](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/maxandreogeret/32/701_2.png) [@MaxandreOgeret](https://community.ntppool.org/u/MaxandreOgeret)\ **Post date:** [February 18, 2021, 3:52pm UTC](https://community.ntppool.org/t/serial-gps-sync-help/1911/9 "2021-02-18T15:52:40Z")
The GPS is already connected through ethernet to the computer and I can communicate through the ethernet connection. Also I can enable a PTP server on my GPS. Should I enable it and sync my computer via PTP over ethernet with the GPS ? Would the time accuracy still be good ? Thanks !