The most accurate Raspberry Pi atomic clock IN THE WORLD!

Will the fabric of space-time be split if I plug this highly-accurate Rubidium-oscillator-backed Time card into the Raspberry Pi?

Probably not, but we'll test the driver on the Pi, probably recompile a kernel or two, and learn about Linux PTP networking and GNSS-based timekeeping along the way!

Mentioned in this video (some links are affiliate links):

#RaspberryPi #TimeCard #OpenComputeProject

Contents:

00:00 - Meet the Time Card
01:16 - Who needs a nanosecond?
03:49 - Board tour
05:18 - Plugging it in
05:56 - Time Card driver
07:12 - PTP on the Pi
09:30 - There will be more...
10:44 - Outtro and outtakes

[deefdragon]

The technology connections quip.... take your darn like. seriously tho, I cant wait for a video showing off two computers with the EXACT same time using that hardware standard

[rougenaxela]

1:13 Okay, I just have to call this out. The "> 200, 000x more accurate!" card here implying that a higher frequency makes it more accurate (or that these two frequencies even related to each other in a meaningful way) is **highly** misleading, straight up wrong even. Higher frequency does not mean better, not in the slightest. You can have a 1THz oscillator that is absolute garbage at keeping time. What matters for an oscillator is it's tolerance, stability, and phase noise. In this case since the oscillator is GPS-steered, tolerance matters slightly less, but stability and phase noise are still critical, and this is what something like a rubidium oscillator excels at, but it has nothing to do with how high a frequency it is, it has to do with how stable that frequency is, how little it shifts due to both environmental conditions and random fluctuations. Now, there are technical reasons related to phase-locked loops (which is used to get a different frequency out) why an underlying frequency standard should be reasonably high frequency, but that's not what sets quartz and rubidium oscillators apart from eachother, you can get quartz crystals tuned for the GHz region. What sets it apart is that a rubidium oscillator depends on atomic scale properties of electron energy levels in individual rubidium atoms which are relatively fundamental and unchanging, rather than depending on the relatively 'macroscopic' properties of a chunk of quartz crystal as a whole which depend on physical dimensions and environmental conditions.

[keithmiller]

You compile the Linux kernel so often it would be interesting for a video of how to do it. Just a suggestion.

[MarcoGPUtuber]

An atomic clock? It's everything I've ever wanted! It will finally ensure I am on time for work. I always end up 1 ns late. Got written up for it too!

[famitory]

love when open source projects like this come out, not because of the projects themselves, but because it makes the appliances they replace drop in price on the used market. finally, an evertz msc5700 for my very own home

[Wordsnwood]

You're making me nostalgic, Jeff. Setting up NTP / XNTP on our network was my first duty wayyyy back when I got my first job as a sysadmin. Stratum 3 or maybe 2 was about as close as I got, though. Everybody needs accurate time, but they don't realize it.

Also +1 for the Technology Connections comment. Very meta.

[mattparker]

this card is doing the rounds for sure, just watched LTTs vod in it.

[careytschritter]

Please don’t let Red shirt Jeff near the atomic elements. We would risk too much to the North American continent.

[jockinafrock]

I work as a tech support field engineer for a major telecoms provider. Our entire network is synchronised to 3 Caesium clocks, cross referenced to each other and with GNSS receivers. We distribute this sync to our customers, most of whom have no idea of the ramifications.

However we have one customer who are halfway through migrating their entire platform from TDM (i.e. E1 2Mbps circuits), to Ethernet. Because of the mixed technologies, their services are critically sensitive to clock jitter, and we are spending a fortune in analysing, adapting and managing their circuits to reduce these issues.

I have been using Symmetricom Rubidium / GNSS test equipment as reference clocks to monitor their circuits, and the tolerance levels are so miniscule.

Great video.

So this is the third video I watch about this time card, yet you've added a ton of new info which I was not aware of. Like how Linux identifies the card, or that PTP requires hardware support on the network interface to work. I got a bit more excited about the possibilities this card offers. I was stuck in my head thinking on the database level only, that you can organize transactions in such way that you can essentially use optimistic locking all the time and non of them will collide. As a developer I thought "yeah, that's cool", but it's the more practical use cases which opened up my eyes. I'm really looking forward for the next video in this topic :) Also, I was thinking the other day about making a GPS based NTP time server on my network from a Pi, because "I can"(tm). GPS radios are not that expensive now. That could also be a good intro video to network time services. Shame on me, I never had the urge to look up how even NTP synchronization work, and PTP was completly unknown to me before this card. But it's an interesting topic.

[vincei]

The Rubidium unit on the card generates a 10MHz TTL clock. I have working Symmetricom Rubidium clocks that were bought a fraction of the $700 for the Microsemi unit so I think I'll go head and build one of these and connect it up to my existing 10Mhz TTL reference. Thanks for sharing, Jeff. Oh, and this is the best coverage of this device I've seen to date.

[Itsdirtnaptime]

I love the Technology Connections reference. It is great when people reference other channels, especially when they aren't in the same category of films.

[urfriend]

Your humor and great work is, in my opinion, the best “family friendly tech channel”. I am eternally grateful for all your great work.
I will keep sending you, and love ones, endless great wishes and blessings.🙏🏻

[IamYuto]

It's always nice to see you giving a shoutout to small content creators like Linus.

[MarcusPHagen]

Once again, Jeff, you provide a thought-provoking video which has me spending even more time reading through the debates & information in the comments. I'm grateful for the level of engagement that you have with your viewers, as well as as the way in which you accept corrections when additional information is presented by others.
Yours is one of my favorite channels, providing both information & humor. I wish you a long & successful run.

[DanDrown]

Thank you for the video, I'm excited to see what you can do with this hardware. I have a few responses to your video:

- The rubidium clock's accuracy is not based on it running at a higher frequency than quartz, but rather a more stable frequency. Temperature changes cause quartz crystals to change frequency more dramatically than rubidium


- The 32khz crystal runs the real time clock (RTC), which can keep time between reboots. The RTC is typically ignored on the pi because it does not have a battery backup for the RTC, so the program fake-hwclock is used instead. The main system time comes from a counter in the CPU on the pi (driver is named "arch_sys_counter") which is driven at 54MHz

- NTP can use hardware timestamping as well, and can reach microsecond to hundreds of nanosecond levels of sync in proper conditions

[ImprovisedExpletiveDevice]

That's pretty cool. I just picked up an HP5065A, an old school Rubidium frequency standard. Lot of cool things you can do with a super accurate clock.

[thecorley]

When I got to my first submarine, we used 2 cesium clocks to provide reference signals to most of the equipment. The Cesium clocks weighed about 75 to 100 pounds and we had to take them to get calibrated every 6 months. They had a battery backup that lasted about 20 minutes, so we had to get them to the shop quick. On my last submarine we used a rubidium clock. Smaller and cheaper is better. We could sync it up with GPS ever few days to make sure it stayed accurate.

[ghostdog]

3:30 Many time standards (at least in my grandfather's collection) are 2-3U rack mount chassis, with about a quarter to a third of that space being the cesium beam tube in its high-vacuum housing and oven. The size difference is truly dramatic.

[BrianBoniMakes]

Another bleeding edge RPi episode. I'm interested in following where this goes.