The Raspberry Pi as a Stratum-1 NTP Server

  • I just built one of these. It's fun to have a little computer that can synchronize highly accurate time without an internet connection by listening to things in outer space!

    I built an auto-install script that anyone here is welcome to use or reference[1]. If you know what you're doing, just change the GPIO pin to your PPS input and fire away.

    Unlike the author I used Chrony instead of NTP. It's lighter-weight and much easier to configure with a PPS/GPS reference clock.

    The GPS chip I used was an ATGM336H, which can be had for less than $8 on ebay. I'm able to lock consistently 11 satellites from my desk[2]

    Keep in mind the Pi has no hw RTC. If you're doing this for fun spend a few more bucks and buy an rtc chip from ebay so you don't drift considerably between being powered off.

    1. https://github.com/stephen-mw/raspberrypi/blob/master/roles/...

    2. https://www.ebay.com/sch/i.html?_from=R40&_nkw=ATGM336H&_sac...

  • I had one of these running with a 10 meter cable to the window so the receiver could get enough satellites. After 24/7 for about a year it just died and I haven't had time to figure out what's wrong. Lights blink but it's not reachable via ping, ssh or scp. HDMI output shows nothing. I had to move on to other projects, so I gave up and assumed I either got hacked or I hit the cheap-SD-card problem of corruption that seems to plague other users running their Pi continuously for longer periods.

    I've started buying SanDisk's "High Endurance" microSD cards hoping it will mitigate any such issues in the future, but I haven't had time to get the NTP set up again... I really should have cloned the image.

    I think the hardest part was finding a case with space for the GPS hat[0] with an open end for the coax connector. The hat sits a bit crooked because of something bulbous on top (condensator?).

    [0]: https://store.uputronics.com/index.php?route=product/product...

  • Maybe add [2012] to the title, dear mods?

  • Off topic: I love this couples website. If you click through to the homepage they've got lots of stuff to browse.

    Yes, it maybe old-style, but it's these sort of sites that the internet was originally built on. It's a real shame that they are becoming a dying breed.

  • > Configuring Wi-Fi

    That alone will negate any benefit of running a stratum 1. You lose the precision and accuracy over wifi. Jitter on intranet with the pi as a timesource would be magnitudes greater than the GPS link.

  • this is pretty cool. i was looking at your case, could you tell me the exact model case you were using? i couldn't find the exact model on modmypi.

    also, here's a writeup i did on my experiences creating something with an rpi 3 model b+:

    https://github.com/stephenhu/written/blob/master/raspberrypi...

  • What is the use case for microsecond-accurate timekeeping?

  • I built a nixie tube clock like that with a gps receiver, it works amazingly

  • They still haven't separated the USB/Ethernet Bus :/

  • Are there performance differences regarding Pi 1/2/3?