# Ordered me a new GPS

**URL:** <https://community.ntppool.org/t/ordered-me-a-new-gps/3251>\
**Category:** Server operators\
**Created:** [February 17, 2024, 7:41pm UTC](https://community.ntppool.org/t/ordered-me-a-new-gps/3251 "2024-02-17T19:41:31Z")\
**Posts on this page:** 1\
**Showing post:** 42

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**Author:** ![ddrown](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/ddrown/32/11_2.png) [@ddrown](https://community.ntppool.org/u/ddrown)\
**Post date:** [February 29, 2024, 4:27am UTC](https://community.ntppool.org/t/ordered-me-a-new-gps/3251/42 "2024-02-29T04:27:21Z")

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> [@stevesommars](#):
>
> If PPS is delivers this: PPS → serial/USB converter → Computer (with USB),  
> The jitter depends on the serial/USB converter. I saw ~1 msec jitter with an old converter (e.g., USB 1). With a USB 3 converter the jitter was only a few microseconds.

I’ve done some tests with this, and wrote my own firmware for a custom serial/USB converter. It can still talk USB Full Speed / High Speed, but provide timestamps between when the PPS happened and when the USB host picked up the carrier detect message. This was good enough for a time sync error of 7 microseconds.

Full Speed polls at a minimum interval of 1ms, which explains your results.

I have more detail and the code here: [ch32v307 dev board, part 4](https://blog.dan.drown.org/ch32v307-dev-board-part-4/)

I’ve been meaning to design USB GPS hardware board with this firmware, but I haven’t gotten around to it yet.

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