The official abbreviation for Coordinated Universal Time is UTC. This abbreviation comes as a result of the International Telecommunication Union and the International Astronomical Union wanting to use the same abbreviation in all languages. English speakers originally proposed CUT (for "coordinated universal time"), while French speakers proposed TUC (for "temps universel coordonné"). The compromise that emerged was UTC,[6] which conforms to the pattern for the abbreviations of the variants of Universal Time (UT0, UT1, UT2, UT1R, etc.).[

Having worked on PTP professionally, I know that a few years ago big players used to charge $1,000,000+ to license the software for the algorithm that does the synchronization. Then it would still take many months of work to integrate it into a working product. The fact that this is open source is awesome!

They should have more of those WWV type of transmitters all over the US and force auto makers to tune into it for turn signal flashing. No more sitting at red lights watching a bunch of flashing lights sync and unsync.

Glad to see you and Dr. Byagowi debunking the radioactive hype. Looks like the average Rubidium oscillator consists of 160 picoCuries of radioactivity. For comparison, your average banana measures in at 520 picoCuries. And you *really shouldn't be eating* any Rubidium oscillators you find lying around. During undergrad physics we did a ton of experiments with radioactive button sources and a few using our college's very own neutron source. At the beginning of every lab we were given a safety lecture about the proper way to handle... the bricks of lead we were using for shielding, because those were the real health hazard.

I have used PTPv2 in wind tunnels, where multiple computers record audio signals from a few hundred microphones. The data is all timestamped, which allows software post-processing to calculate where certain sounds came from. The same effect as a dish that your would physically move. For this to work well, you want nanosecond-scale accuracy. And since wind tunnels are generally large metal structures, running a GPS antenna for each computer is not preferable.

It's about time!....to watch Jeff Geerling!

The T-shirt was well Co-ordinated also... ;-) My first job as a sysadmin 30 years ago was setting up and managing xntp on our network, so this takes me way back. Back then you had to ask permission to have our servers "ping" off of a university's stratum 1 clock over in the next province. It's fascinating to learn how NTP is not accurate enough these days. But wow, a Stratum one clock for so cheap sounds amazing. And no, it did not impress the ladies back then either. 😆

I did an internship at a telecom company, every piece of lab equipment (network switches, oscilloscope etc.) was modded to be able to use the same clock signal via bare (coax) cabling.

I've run Stratum 1 servers from RPi 3s for a few years. While testing code for NTPsec, I had a group of 4 fed from the same antenna with carefully crafted cables to ensure that signal path was the same for each device. This was used to experiment with convergence differences between different NTP solutions. Also, my first professional presentation was on time synchronization using xntpd as one of the options. I also have code that is part of that project for adjusting the time in the kernel to reduce drift, basically adjusting the value of each 'tick' to account for the variance in the systems base oscillator.

Got many CM4's on order, in the meanwhile, the sun is out today so the master clock in the garden (sundial) is all we have! PS, black for signal and yellow for ground???

We use ptp to coordinate audio and video over a network in the Audio Visual field. It allows us to get video walls synced up for making sure they are frame accurate. We actually don't care about the exact time just that all the device are synchronized. It also means we have to use somewhat specialized switches that support QoS and non-blocking.

2:40 Radio Clocks "...will sync-up after a few minutes..." Only locally, from a 'continental' perspective. More-distant locations will have to wait until the wee hours (e.g. 2:00 AM local), when the VLF signal can reach their location.

Jeff, On that scope you can use Measurements to measure time between the two pulses so you don't have to count ticks. You can also use Cursors to manually get a time delta by placing one cursor on one pulse and the other on the other pulse. Measurements and Cursors are very powerful tools in the scope and it's well worth the time to learn how to use them. Best wishes.

Nice job on finding yet another Raspberry angle on something I didn't know anything about! I loved the vibe and enthusiasm of Ahmad!

Fascinating. I love all of the things you can do with a RPi. Great video!

I get pumped when I see a Geerling notification in my feed. I know I'm gonna learn something cool.

"Maybe i'll be the first homelabber with a time server in my rack" Sorry to break it to you, but that prize was handed out a long time ago, even on a Pi. Running GPS based stratum 1 servers on RPIs has been common for long.

This video is a godsend. I am currently working on a project where positioning is determined based on Time Difference of Arrival between two signals. Even though the project is in very early stage and we don't need perfectly synced devices right now, but eventually we'll need it. Else nothing will work. Thanks for making a video on this topic. It'll definitely help me immensely.

One of the most unique and interesting videos on the channel so far!

I made a gps based ntp server with my old pi a few years back. it used the PPS on that gps chip. It was fun

Jeff showing off 2 RPi CM4 when it's hard to get your hands on a single one 😂😂

Always great content

Amazing video, Jeff! 💪🏻

I love videos like this, though this issue in time syncing doesn't affect me personally. I am fascinated by it because the lengths people go to, to perfect solutions like this is impressive and greatly underrated by the majority. I can't help but and geek out about videos like this. Keep up the great content Jeff!

Very interesting and very educational. Excellent job Jeff.

Seriously impressive progress!

Cool video, never knew time could be managed at home with my own server. When CM4 prices comes down, maybe I'll install it next to my Pi-hole! Thanks again for the video, I only wish you would post more often!

Loved this video. Beautiful , elegant explanations! And to boot on a PI! woooo hooo

Thank you very much. It was a new experience for me.

Absolutely amazing - Thanks!

Thanks! Very interesting stuff.

Excellent video Jeff. I would love to see a video about the PI’s ability to generate a reference frequency. Not a reference time via a pulse interval. The frequency domain is very important for synchronization of communications. You know as in frequency hopping spread spectrum. If the PI could give us a cheap way to generate an accurate frequency it would enable all kinds of elaborate data exchange at a very low cost. It would be a game changer.

Informative and got me thinking (This is where I usually get into trouble)

What a strange coincidence. I saw recently that VMware 7.0 supported PTP as a time sync source, which led me down the rabbit hole of all this stuff. Very cool video!

Pis are getting more and more useful! I'm never going to get one at this point..

As someone who went through the hassle of researching and waiting until I could snag a good deal on a used enterprise GPS clock, I'm stoked to see how accessible accurate NTP / PTP sources are becoming for the home lab community now. (Yeah, you're not the first, and neither was I, but hey, it's a cool club, and we're happy to welcome you!) I want to warn anyone who's eyeing old enterprise gear, make note of how long it's been end of life, check whether you can get firmware updates without a[n expensive] support contract, and verify that it was updated recently enough to handle the GPS Week Number rollover on April 6, 2019. The oldest and most affordable stuff out there cannot, so it's basically useless, and the gear that's new enough to still work is not as affordable as it should (IMHO) be. Caveat emptor, and whether you go refurbed enterprise or DIY, happy timekeeping!

Love the channel

This is really interesting, once more available I might get one

This is fantastic for me. I have equipment that uses GPS for timing. Last year some of the GPS units stopped working and the equipment defaulted to NTP, which was not accurate enough. I then discovered they could use PTP, but the cost of a server was too much for me. Now maybe I can implement PTP.

At work we're looking at using our Cisco ASR routers as PTP GM clocks, with GPS reference. It looks like it's a pretty straightforward setup, so I'm sure there's more than a few CCIE types who would have this set up in their home labs. Granted a couch change raspberry pie is a lot cheaper than a $100K router, but businesses retire these things all the time, and it's not uncommon for equipment to be redirected from the e-waste bin to employees' home labs. (EDIT: Not that I'm speaking from experience.)

Great video as always Jeff, but I have to admit that for me the star of the show was the shirt you're wearing - I want one of those!

You tease us so much. Most of us will not get our hands on ANY sort of RPi this year (or next, the way things are going). So you may as well do projects with, or educate us on, the hadron collider.

A few years back I had a Raspberry with GPS as the only time source, because that RPi was used outdoors without any network connectivity. I remember extremely good how I struggled to get GPSd and NTPd talking to each other.

This is a great post.... I just did something exactly like this... My Pi Hat uses multiple GPS sats to give me +/- 400ns time /date and I use NTP to get it to my networked servers...

Well thanks for making those board more rare.

Jeff.. look at the timing features etc for the upcoming WiFi 7. 802.11be includes full QoS and time services so all your wireless devices can also sync.

Awesome video, thank you!

Tom Scott he's amazing his videos are super informative and easy to understand the bcz the he explains about things in a simple way.

I did some work with small 4g pico cells, the ones outside used GPS for time, the ones inside we fed with PTP from our backhaul radio equipment. That had a GPS and generated the PTP pretty much as the PI is doing, we had a load of interest from companies that wanted the GM functionality and didn't need the radio link. I left soon after, always wondered if it went anywhere was cheap compared to a GM IRO of $1000 IIRC but maximum of 6 slaves, would probably do more but that was all we tested. Somehow the solutions now are going to be way cheaper and this was only 6 years ago.

Jeff ur videos always motivate me to go play with PIs but then I remember that I need to buy some 😭

Really cool stuff!!

The Dante audio protocol actually uses PTP to sync all of the audio packets that are traveling over the network.

Thanks, an amazing lesson.

Thanks!

Some guy made this idea work with starlink aswell, so eventually getting the starlink dish and router might throughput PTP through existing LAN cables.

You say "Until next time I'm Jeff Geerling", but every time you come back you are Jeff Geerling again! 🤪

PTP works by using profiles and the size of the network, routers, switches, etc are taken into account with PTP. PTP measures the end to end latency form the client to the PTP server to calculate the loss to maintain time sub microsecond.

PTP is my favorite clock!

Thanks for adding actual captions for the Deaf

You learn alot from these comments 10/10 video

12:26 "I use this material to pick up girls." "Hey girl, are those clocks atomic? Because you make my heart go tick-tock." I'll see myself out.

For test bench use, a GPS Disciplined Oscillator (GPSDO) can be useful. They're about US100. 'BG7TBL' is one designer. These gadgets contain an Oven Controlled Xtal Oscillator (OCXO), brought into alignment to GPS by a uC. They typically produce plain-Jane digital 1PPS and 10MHz signals on their front panel BNC connectors.

Fancy scope !

Jeff: Nerdy about time Me: Doesn't even use a watch anymore

I have dealt with GPS time devices and can't wait see the time hat.

Sometimes the answer to a problem is NOT a raspberry Pi. Jeff Geerling 'Hold my beer!'

Wow, the day after Sam at THIS MUSEUM IS (NOT) OBSOLETE channel shows us how to build our own master clock, we get this!

Welp. Definitely learned some new stuff here!

I've been playing with GPS PPS on a Pi4 and Sparkfun GPS module and getting nanosecond level accuracy. Your statement about GPS is accurate though. The better the access to open sky the better the accuracy. Nobody needs any of this for home network stuff but it sure is fun to set up your own PPS server for a few bucks.

2:26 I just picture Jeff toiling away with a soldiering iron while WWV plays in the background. 😄 that's true geek cred.

watching this in the car over Bluetooth. quite ironic I'm watching a video about precise time keeping & syncing. and having the audio 2 seconds later than the video!

Thank you

Jeff is genuinely nice as pi

I know a project with this in mind. Central clock replacement. I think there still is a lot of old mechanical clocks needed to be replaced by a raspberry pi.

I can guarantee you are not the first with a PTP time server in their home lab. I don't remember who it was, but I remember seeing that someone had multiple atomic clocks in his homelab. This guy even did a test with him going up a mountain with the atomic clock and getting down and comparing two clocks.

GPS also has the roll over issue which can be fun to deal with. Do the cards have an auto update feature so they don’t fall victim to the GPS epoch issue?

I always get hyped up from these videos to have extra precise network time on my LAN for no apparent reason; your presentation is great. :D Is there such thing as a database of NICs to see which support PTP protocol? Eg. can I check somehow if an onboard LAN on a motherboard supports this or not? Because having a CM4 PTP server is just one part of the equation. I guess the big investment is going to be on the PC side.

It's worth mentioning that 1PPS signals (done correctly) are aligned with UTC seconds, so that all the 1PPS signals on Earth should transition (upwards) at the very same instant.

Stop buying all CM4 I can't get my hands on one :) Very educational video. I look forward to see that applied to online gaming

it's about time for a raspberry pi time watch

I am looking to implement PTP on a LAN that runs Dante audio equipment. This sounds like a good project

very interesting, i work in managed IT infrastructure and i notice that good time synchronization is often overlooked, most sys admins only care if it's accurate within a few minutes which make me die inside 😭

There are network switches that can fan out PTP. So if you connect the Pi to a few of those switches, you don't need those expensive grandmasters. In this case those switches handles downstream devices however many of them, and aggregates all of those into one PTP stream from the Pi.

I think NTP and PTP are different usage, PTP and GM clock are for digital transmission usage … this is prevent digital packet collisions and crash. It can apply on device on the LAN, router, switch, ap … etc. and also apply on multicast streaming … like SMPTe 2110, Dante AV and NDI. PTP is like Metronome

Nice. With this i will be never again to late to bid in the last second of an ebay offer 😁 Some of us are happy if their windows clock isn't out of sync by hours. "Sorry, boss. I'm not a little late at work this morning. I'm just out of sync"

PTP is also used in the entertainment industry; synchronization for light and video shows.

love the T shirt

Yet another reason to ditch "Daylight Savings Time", with its twice/year shenanigans!

Hi Jeff, thanks for the great explanation about how high precision time sychronisation is possible on the CM4. Have you published any of the code / instructions used in your demo? I would like to try to reproduce the time synchronization between two CM4 modules.

Great topic. I have several Casio watches that have the shortwave radio update feature. They are affordable and amazing. This is a very underrated technology. I recall there was some conversation in recent past about Govt reducing their funding in the NIST program. Hope this never happens.

My dad would listen to the WWV every week to set the 50+ clocks in our home.

How did you find the time to do this? What would be a good project/task for an RPi that would save you the most time and with that, wished some projects showed the return upon time investment as if a day spent can return a day in a year, that whole days task becomes more likely to come about. So what would be the best projects you have done for yourself that have saved you the most time? Maybe a video idea is there for the answer.

Wonderfully insane!

when I started to watch this video, I immediately predicted that this video would be about using a raspberry pi to keep track of time. My prediction seems to have been correct.

I often wondered if this kind of signal was being picked up on the Skinwalker Ranch show

The TimeCard uses a Xilinx FPGA, the software to program this is not open source, whilst you can get an open source bit stream to program it, if you want to change the programming you still need commercial software tools from Xilinx these are not open source although they are currently free to use

Very interesting, something I'll need to look into going forward. Wish it worked on regular pi4 since I have that now. Of note, GPS locked NTP devices are not that expensive. Look at Broadcast Tools and Timenet, these are the two clocks I have on my network.

I was going down the rabbit hole of using a USB gps module on my pfsense box and then you make this video. Heh.

Wonderful, thank you!

A few corrections: 1. While strontium clocks do appear to be a thing, they don't appear to be more than experimental at this time. The NIST still uses cesium-based clocks, as well as a pair of hydrogen masers for their production equipment. This is what feeds station WWV and the Navstar GPS satellites. AFAIK the SI definition of a second still uses cesium. 2. WWV is not "a tower" it's a shortwave radio station near Ft. Collins Colorado that broadcasts on several shortwave frequencies. There's also WWVH in Hawaii, and CHU in Ottawa, Canada. 3. Nope, all those clocks do _not_ use WWV to set themselves. They use longwave station WWVB, that's located on the same campus as WWV, and uses the same NIST time base in Boulder CO, but WWVB is a completely different station on a completely different frequency band, and uses a completely different format that's more easily decoded by simple electronics. 4. Pretty much every GPS receiver that's designed to be a stable time reference has a local oscillator using a quartz, rubidium or cesium time base that can either be slaved to the GPS signal, or become free-running if the GPS signal is lost. Other radio signal sources include CDMA cellular receivers. 5. Calling a GPS clock "grandmaster" is silly, misleading and simply incorrect. They don't play chess at all, and in the hierarchy of master clocks, they're at the bottom. The cesium clocks aboard each of the Navstar GPS satellites are superior to the user segment clocks on the cards, and the cesium beam, cesium fountain and hydrogen maser clocks at the NIST and Naval Observatory are superior to the space segment clocks. One could argue that the _Bureau International de l'Heure_ in Paris is superior to NIST and USNO, but when one considers that the National Bureau of Standards, the predecessor of NIST invented atomic clocks, the technological home is in the US.