Nanosecond clock sync with a Raspberry Pi 

Like how iso stands for international organization for standardization, sometimes the acronym doesn't match in all languages

@@JaredConnell roughly the same reason. Additionally ISO is derived from the Greek word isos, which means "equal". The more you know... 😊

I just think of it as "Universal Time, Coordinated" and move on.

UTC stands for Universal Time Coordinate and refers to the baseline that coordinated time is set from (which is why it is represented as UTC+x).

So yes.. the acronym is correct.

I can't fathom why people care so much about this.

@@tim-w Do you use a cell phone? Tight synchronization is vital to making the radio network work. There are many other applications, but this is probably the one normal people interact with most often. The electrical grid also relies on tight synchronization, but the transition to digital is happening more slowly as they are ultra-conservative in that industry.

@@tim-w Making cell phones networks possible. Making GPS possible. Making banking transactions secure. Proving relativity. Calibrating equipment not to mention more serious applied and pure scientific research.

@@tim-w I currently have better than 1ns timing jitter between my Grandmaster and switch using PTP and Synchronous Ethernet in my home lab and the GM is accurate to about 40ns of UTC. As has been mentioned, timing is critical in communications systems. It is looking likely that 5G will transition in later specifications to a requirement of 5ns timing accuracy. It is fun to play with but there are absolutely real-world applications for sub-ns timing. In the industrial networking space accurate time is needed for synchronising different parts of a production facility and is provided by industrial field bus systems such as EtherCAT. With standard crystals I’ve had better than 20ns of timing jitter between devices on a network. One of the problems is that the GNSS constellations such as GPS, Galileo, GLONASS etc are prone to blocking so it is common to have multiple Grandmasters which may be 100’s of miles apart for resilience. In the UK there are exercises where GNSS is deliberately blocked and these are listed on Ofcom’s website. IT is also possible to have a GNSS firewall where if the GNSS signal is blocked the timing can be sourced from either another remote GNSS Grandmaster or a local Caesium / Rubidium clock. Accurate time is also critical for trading to track when exactly a transaction is placed and also in cars. Many new automotive applications rely on time for position doing and synchronising RADAR systems for spatial awareness.

Oof, this makes me think of how big companies will use open source work, not contribute, and then try to draw away attention from the open source work by rebranding and popularizing their own version that builds on it. I’m thinking about video capture software, that most streamers use. I hope whoever decides to make use of this put in a few of the millions into the work.

Hahaha, I actually made a similar comment on a Technology Connections video about turn signal timing :D

Make the whole city blink in sync, would be a nice sight on a dark night, it would probably reflect in the sky :)

I love that

@@JeffGeerling I was just about to mention Alec's clip on this, and you beat me to it.

You can just use cameras already in cars for this. :-)

I would also recommend against eating bricks of lead :D

Thank you for the explanation Gilad. It makes me feel more safe playing with these toys :)

@Astrocat 3D I'm pretty sure he will let us recompile the Linux kernel

Must be why I glow in the dark, I eat a lot of bananas.

@@anon_y_mousse This issue came up. Person in the class asked if they should be worried about their radiation dose because their significant other's diet was so rich in potassium. Physics professor replied, with a completely straight face, "Well, dosage vs. proximity follows the inverse square law."

[First date] Would you like to know how accurate my clocks are?

My clock's more accurate than any other out there.

large metal structure, like an antenna ? ;-)

@@jyvben1520 Like a faraday cage, about 20 meters in height. We try to keep the computers close to the microphones (near the ground) and they're generally standing in the wind (300kph). Running long wires in that environment doesn't seem wise.

What are you using microphones for in a wind tunnel and is it even possible to do acurate audio location when wind is a factor?

@@hyperfluff_folf about 50% of aircraft noise comes from the engines. The rest comes from the aircraft itself. Landing gear, flaps, but also small gaps between components. Since noise of landing aircraft is a big factor for airports, manufacturers want to find the sources of the noise. This is generally too complex to simulate with a computer I'm told. You are right that wind is a factor in the propagation of sound. These effects have been modeled, and we apply corrections to our measurements in an attempt to undo these effects. In order to apply the corrections we need to know things like wind speed in the wind tunnel, so these are measured too.

@Richard Cranium Yep, where PTP is used you sync after the fact. In general the strategy in measurement systems is to directly store your measurements on disk, unmodified. Wind tunnels are expensive to rent, so you want to have your data to pass through as little lines code as possible. Every line of code is a possible bug, and you cannot recover from bugs in your acquisition code.

True, true.

Haha I was wondering if someone would notice. I had plugged them in backwards from the pins I thought they were and just left 'em.

came here only for this comment 😅

If you think about it, on a sundial it is black for signal and yellow for ground.

Are they purple switches?

@@PsRohrbaugh honestly for video we end up using the Netgear av line switches. They come in a good range of sizes and configurations preset that's make manufacture specs for encoders and decoders. faster and easier deployment that way.

Yes Jeff great video you always go beyond the content details I expect too see. Great work!

About 20 years ago, I read the Linux NTP README and discovered that I could buy an obsolete GPS receiver for $25 and a serial cable for another $10 to turn pretty much any Linux box into an accurate NTP server. The hardest part was making a battery eliminator, so I didn't need to keep replacing the AA cells in the GPS receiver. Today you could probably use an old cellphone and a USB OTG cable for next to nothing.

@@StringerNews1 mini pcie and M.2 lte and gps cards exist

@@StringerNews1 afaik there are GPS/modem modules with serial interface for around 30$ to be used for Arduino, drones and other microcontroller-based stuff

@@bobbydazzler6990 why are you asking me this? I've never found a 1 Hz tone useful for anything I do, certainly not a replacement for the standard 10 MHz tone carried over a coax cable. I was talking about making an inexpensive NTP server, as was the OP. If you really need to count one second intervals, you could use the phone's clock or something. What exactly is your use case?

@@bobbydazzler6990 sorry, but I'm not your parents. You're not entitled to my time. You're acting like I owe you something, and that's simply not true. If you want strangers to respond to you, try asking nicely, and learn how to hold a conversation.

Indeed. I currently live in the next state over from where the WWVB transmitter is, and my "atomic clocks" that use WWVB typically need several tries to sync up. The best case is they start at midnight, and finish at 12:04, but it's not unusual to have them trying again at 0100, 0200 ... all the way to 4 AM. When I lived in Chicago, these types of clocks almost never synced up. Too much electrical noise in the city.

What I meant was an atomic-clock-based PTP time server. No other *Pi*-based setup can do that besides a CM4 (and only recently at that).

WiFi 7 will be quite interesting. Borrows some features from 5G (which also uses this kind of timing accuracy to get the bandwidth it does).

He crams a good amount of information into a short video that illustrates what he's talking about very well.

@@JeffGeerling yeah 👍

It sounds like it's _time_ for an upgrade!

@@JeffGeerling ba dum ts xD, good one

But only if the network switches and other gear actually support PTP. If they don't, then you won't have a way to get the PTP signal across LAN segments so that the clients can talk to the server(s).

You're right, sometimes the answer is RPi-Pico, or 42. 😉

@+①②①④⑥③⑨⓪③④WhatsApp Oh wow definitely will "Jeff"

hahahaha...only the geeks will buy this pick-up line. =)

Unfortunately, it seems like IEEE1588 support is often buried in tech specs for NICs :( And not all that support it really seem to have full driver support, either. It seems like Intel is the best bet, even many older NICs support it (e.g. i210 I think).

@@JeffGeerling so this will take some "time" (ba dum tss) to get mainstream unfortunately. :(

PPT also works with software time stamping. We have a Raspberry Pi 4 with a GPS Hat (with PPS) running as a PPT Server. We use this to time sync our web server which is located in the basement where we haven't any change to get a GPS signal. Using software instead of hardware time stamping reduce the accuracy to the micro second range. But that's at least two magnitudes better than using NTP from a time server via internet

@@ChrisA4A4 True! And I didn't even touch on that ability. And from some further investigation, it looks like it's _possible_ the chip in the Pi 4 could have 'unofficial' support for hardware timestamping, too.

https en wikipedia org /wiki/SMPTE_2059

Also AES67 for broadcast! I'm hoping to explore that a little more with my Dad (radio engineer) on a Geerling Engineering video in the future.

I have been replacing clocks in my house for a few years. I have four pi zero (original, w, 2w) based clocks scattered about. Two are clocks ONLY. Two have clocks in the UI; but, also play audio from my home server. I have a pi 4 based GPS enabled NTP server supporting all my networked CPUs. My wife puts up with me. 😁