Another potential quip but perhaps was intentional, there was a seemingly intentional use the term "MOST PRECISE" in the video. In the clock world I'd imagine the term "MOST ACCURATE" , used in the title, would have a substantively different meaning than the phrase "MOST PRECISE" To my non-nerdy audience here: An accurate baseball pitcher consistently throws strikes within the zone, while a precise pitcher can consistently pinpoint specific locations within or around the strike zone.
I've gone so far down the rabbit hole of Pi-related acronyms that, for the first few minutes of this video, I forgot what GPS stood for. This is technology at its finest. Love the work you do, Jeff.
I put one of these in my microwave's control board and now I can finally test my reflexes stopping the cook time down to the nanosecond like a true action hero.
It isn't the high temperature that makes the crystal more precise. It's the fixed temperature. It's hard to cool components. So this means the oven is used to raise the temperature well above the inside temperature of the device the crystal will be used in. So assume +50°C ambient temperature, and maybe +75°C inside the device. Then the crystal needs to be heated well above +75°C so no unplanned extra warm day makes the inside of the device warmer than the oven. After they have decided the oven temperature, they will then cut the crystal to be at the nominal frequency at this temperature. That's like how wrist watch crystals can be cut to deliver 32768 Hz at close to 37°C from the arm. Don't use the watch and the crystal gets too cold. Leave it in the window and the watch gets too hot. And this makes the watch drift in one or other direction. A 32.768 kHz crystal for a home appliance is better optimized for maybe +23°C. Somewhere slightly above room temperature.
I could've been more clear there :) But yes, it's easier to maintain a fixed temperature when you heat things up beyond what the typical environmental temperature would be; cooling it would be much more difficult, especially inside enclosures that could vary wildly in temperatures. One design consideration for anyone using this card is maybe try to keep it out of a stream of heavy airflow, no use making that little SiTime chip work harder than it needs to to maintain its temperature.
@@thebamplayer It's very unusual now to use the mains power AC periods for time. It was quite common 30-40 years ago because crystals was expensive then. And older power supply designs made it easier. And in that case, at least for my country, you really would hardly see any drift because the frequency might be just below 50Hz during day but then run at just over 50Hz during night to keep a correct total number of cycles over the full 24 hour period. Just that the removal of old-school mains transformers and instead using switched power supplies means that in modern electronics you now need extra components all the way from the mains-power side. This adds cost - both he components and because of any certification that the mains power is properly isolated.
This is awesome! Looking forward to hyper time-accurate interviews! And a huge thank you for helping raise money for ITDRC. I'm the Florida State Coordinator for the organization and can personally attest to the impact the donations make to help fund our mission. Disasters are never fun, so being able to provide some ounce of hope to the survivors is a true blessing.
Hey Jeff, try picking up CHU and WWV and sending them a signal report. They'll send you back a QSL card in the mail. The neat thing about them is not only are they accurate time sources, even their radio transmitter's oscillation is disciplined by their atomic clocks. 73.
Isn't wwv specifically designated and intended as both a time and frequency reference? (Which is why the frequency is linked to the atomic clock, otherwise it wouldn't be a good frequency reference)
It's nice to have a super accurate time source but distribution using NTP introduces latency making the accuracy of the source largely irrelevant so what's the point? 😮
@@glennmcgurrin8397 Absolutely. WWV-DO and GPS-DO are both a thing. I wouldn't be able to say how much more accurate one over the other is - but GPS-DO is certainly enough to calibrate SHF ham signals in practice.
Another good example for GPS synched clocks are DAB+ radio stations. For DAB+ you don't use a big transmitter for a large area, like for AM, but a lot of smaller transmitters serving smaller areas. GPS is used to keep all the transmitters synced up.
This is so amazingly/hilariously over engineered….and I love it. While you’ll have the most accurate time there, Linus will still be late. Looking forward to seeing this at LTX!
@@JeffGeerlingfor Wan show there is no need for such accurate timing, it just need to be accurate ±2 hours, which means it could be an hourglass with rocks in it 😅
For your display… there might be some some signaling and compute delay in your python. Please check your offset calibration, values, and timing. I.e. set a log flag at the start of your script and log flag at the end (or whenever is appropriate) then use that for your screen off-set, and signaling / ptp / ntp offset. Love the project/product.
It will take a while even with an oven to age the crystal to a reasonable point of stability, we used to leave ours on soak for 2 months to get them stable enough for broadcast use.
I have a Pi Zero running a few little things, including Chrony as my stratum 1 internal NTP, relying on an Adafruit GPS board with PPS. I have a 4x20 screen in an acrylic mount on my desk that serves as my geeky desk clock. It was under $100 all in, and has a few purposes for me.
I have carried lots of interesting electronics and cables through the customs. The important thing - it doesn't smell like explosives. And it's good to be able to have batteries separated.
Yes; I'll be taking the batteries in a carry-on, while the rest will be packed neatly in my checked bag. I've only gotten taken aside for closer inspection one time carrying all sorts of strange contraptions through security :)
Awesome! When I was checking on their current deployments, I saw they were helping some tornado victims just south of STL. They're deployed all over the place!
Welcome to the team and thanks for volunteering! Make sure you join the ITDRC slack community so you can keep up with everything goin on here in Region 4 and around the country.
With all that python between the time source and the user I'm not sure you can claim the most accurate time, the underlying clock might be the best there but that doesn't do you any good if its displaying late by a probably wildly variable margin (at least in comparison to the clock accuracy). Might be the most drift proof clock present however and so be the most accurate eventually. But it probably isn't delivering the time to the display as accurately as the NTP will be on every other computer there, and even cut off over the duration of the event I'd expect the drift of the riff-raff PC's to be less than the inaccuracy caused by using the wrong language for such a hard realtime task! The most real of real time tasks!
The computer itself will be holding time accurately though-honestly the blinkstick and miniPiTFT are delayed enough even with a C library I'd end up with variable ms-level delays for end-user display. The Pi will be offering PTP output over Ethernet, though, so I could still say it's the most accurate time source-just not necessarily via it's visual outputs.
@@JeffGeerling True, and even if you went to the extreme of bare metal programming the blinkstick and screen so it is precise as the CPU cycle allow the LED warm up/pixel change times of those HID devices has a meaningful latency when talking this level of timing precision too. Make sure you serve at least once client with the correct time over the Ethernet as I think you can claim to be the most accurate timesource, but if nothing ever uses the really accurate time it could provide I don't think it counts - the Human interfaces on it are going to be the only things used, and they are not impressively accurate.
I'm currently syncing Chrony with a stratum 1 server hosted at the Quebec Internet Exchange a few km away, but I'd love to have something like this in my lab! By the way it's OCXO, the X being short for Xtal/Crystal.
I used to war drive with my RP4, external GPS and USB WiFi on monitor mode. I captured a WiFi hot spot that was inside a parked cop car, with SSID "Purple Pig". I didn't stop to ask. What's interesting is that your GPS is sandwiched between the CM4 and your PCI board.
Another important difference between the OCXO and the rubidium card is that "board with a chip that gets hot but isn't powered on" is probably a lot easier to clear through customs compared to "board that is radioactive."
Hehe, though any decay in the isotope used in the Time Card (non-mini) would be practically un-detectable by airport security. They would think it looks a little sus though.
There is no radioactivity in a rubidium clock (unless you count the 50 billion year half life of the Rb-87 used in the filter - but with a half life much longer than the age of the universe, it is debateable whether to call this radioactive). Moreover, the clock shown uses a laser light source, rather than a filtered discharge lamp - so it doesn't even have the Rb87.
Ayoo, Loved seeing the m8f! Used it in my Bachelor Thesis where I implemented a OCXO (stratum 2 compatible) PLL chip with the PPS Signal coming from the GPS module. They are (even with the internal TCXO) really accurate and low jitter. Iirc somewhat around single digit nanoseconds compared to our big ocxo gps time reference. And yeah, just around 100$ by their own lol
End application was a phasor measurement unit which sampled the grid power based on the PLL output. Gotta keep good time synchronization when you're making the measurements and phasor estimations on the pi. Really great learning experience on how to measure >time
Having involved years ago in buying ntp appliance + Rubidium oscillator for very accurate time, got a kick out of it. To be clear for a majority of users, ntp/chronyc is enough for miliseconds accuracy as Jeff mentioned... unless your doing trading for accurate time.
Just making sure all understand these: precision: how "finely divided" some measurement is accuracy: how closely a measurement agrees with some accepted standard So you can have a clock which has microsecond precision but is off (inaccurate) by minutes. Or you can have a clock that is accurate within milliseconds but only one second precision.
As soon as I saw that Ublox chip I knew it had to be GPS related. I've been trying to research accurate (especially vertically accurate) GPS for a while now and it's pretty hard to understand as a layperson and there's not much info out there anyway, it seems to be a very niche interest. If you could make a video about accurate GPS that'd be so helpful and I think a lot of people would find it cool.
Could be a fun project! (And there are certainly cheaper ways of getting GPS signals into your main time server if you want to try that to get started!).
Very cool! At some point LMG or your self should do a video on AoIP. PTP is huge in that space. Livewire, Wheatnet, Revenna, or Dante would be cool to see a deep dive on!
Nice video. We used a NavSync timing gps and feed its 10 MHz output to an FPGA and try to derive a 100 MHz signal from gps. This gives a 10 nanosecond pulse period. A cosmic ray signal event in our application is time stamped to 10 nanosecond in theory.
Oooh... if you have a Dante setup it would be fun to see if I could be the PTP source! Otherwise, I'll just gawk at your mics for a bit. I was trying to find a good ENG mic to throw in my bag for the livestream.
Oh yes, I've built a GPSDO before, using an OCXO, a GPS module and part of a PLL chip (specifically the phase comparator). No RPi needed. (edit) and no fancy hundred-dollars GPS module needed either. A $5 ublox7-compatible module is enough, with some skillful programming of its internal registers. :)
It does depend on what level of precision you are looking for, as well as the quality of your oscillator. My experiments with some of the cheapy ublox devices, show that they can easily show time deviations of +/- 100 ns, meaning that frequency stability at 100 seconds is only 1ppb on average (there can be larger excursions if there is a change in observing conditions). However, in the event that you need better absolute time precision, or a better precision frequency reference, then improving the GPS receiver may be needed. One interesting thing about making low cost GPSDOs is that obtaining "well-used" obsolete OCXOs from aliexpress is not just cheap, but the crystals are "pre-aged" and often have extraordinary stability. I've got a bunch of the $2 OSC5A2B OCXOs, and when using these for a GPSDO, the limting factor (by a huge margin) is the GPS receiver - you need to use PLL bandwidths in the order of 200 uHz, otherwise the GPS noise gets through to the output. I've got a couple of somewhat more expensive, old SC-cut OCXOs from Ali (about $50 each), which when measured significantly outperform the specifications of the rubidium oscillator shown in this video ( < 1x10^-12 adev @ 1000 seconds) with some software temperature compensation. That said, these miniature rubidium oscillators are a lot worse than the older ones. The laser based CPT method used in the miniature versions has much worse stability than the old-school rubidium lamp and microwave excitation design.
Rubidium clocks use the oscillation of the atom between two different excitation states as their clock reference, NOT radioactivity. Rubidium-87, the isotope used in atomic clocks is NOT radioactive.
NTP tested against the 1PPS goes more on the order of 3 .. 10ms and occasionally worse than 10ms. With the Pi 4, you can test against the Pi clock to about 18 ns resolution. If you take in the 1 PPS and set up an interrupt, then you'll have sub-microsecond accuracy for time - even Jeff should be happy with that? So - you only need the serial output from the uBlox receiver ($50 - $80 at Sparkfun) breakout board for GPS data and the 1 PPS signal. I implement this in RTL rather than Linux. Of course this is not within a PC.
If you're using interrupts to capture time then it is likely that you have 10s to hundreds of microseconds of latency and considerable jitter. Linux is not a real time operating system. Interrupt latency varies wildly and is considerably faster in kernel space than user space. Hardware capture timers are needed for real accuracy.
@@therealtimwarren I'm not using Linux (as stated above). It's a barebones/bare metal set up. Latency and jitter verified against the Pi-4's 54 MHz clock of the system - indeed, with the 1 PPS I can also accurately characterize the 54 Mhz clock''s accuracy as 9 .. 11 PPM (on my Pi) depending on temperature.
Pretty much all the use cases listed (banks, remote ground stations, distributed computing) use GPS - namely GPS trained high stability rhibidium for a few weeks of holdover, and GPS trained cesium for anything that needs to operate during WW3. You wouldnt use OCXO for anything where you'd lose your better reference for any ammount of time. You can use OCXOs for lower cost signal generation while trained to something else.... Like generating a stable multi-mhzs signal off a stable 1 pps. But that stable 1 pps needs to be driven by something with significantly better holdover.
@@JeffGeerling The project is fun overkill - just that little bit of the video ran contrary to my industry experience. I agree they have their uses - I've used them myself to save costs - but how this class of oscillator is used (generally) isn't holdover due to lack of comms (which is how I interpreted the video).
@@garretthaney9134 True; and to be honest, I am only dipping my toes in the water of higher-end use cases. I would rely on your opinion more so than mine!
You know that used to be completely true, but there are now “super” OCXOs (made very well with dual oven type designs) that outperform many chip scale atomic clocks…
It's well into the third quarter of 2023 here in Canada and the availability of Raspberry Pi 4 has still not arrived. I still have hope that Upton's promise will come true.
I've seen PiShop.ca getting stock at least a couple times a week lately. Down in the US it's available somewhere at least a couple times a day now, and it'll be in full stock soon.
The Ublox modules are fairly cheap, They are available on boards for drones. The OCXO is used for the 10MHz output that is used to sync test equipment. Check out Timenuts' if the subject interests you. I have two Meinberg GPS170PCI systems which is a computer card, and a GPS outdoor antenna with a nice molded plastic mounting arm that clamps around a mast, or tower leg. I have a Vk-172 Ublox 7 USB GPS that plugs into a laptop for field work.
Yeah; U-blox makes a HUGE variety of GPS modules. This high-end one includes the capability for external oscillators and a much better internal TCXO too (100 ppb I think?).
What I got from this video: The Apple watch is so bad that you can't use the stopwatch on it, so you applied maximum overengineering and made this? Neat!
I have to use this whole setup for my master thesis and my prof doesn’t even have a budget for it. I’m just settling with NTP implementation and hope it works😅 Not sure it would give a good result at the end for my distributed systems algorithm.
So many of my favorite tech creators are all headed to LTX (JayzTwoCents, Sara Dietschy, Jeff, Snazzy, etc). I'm gonna have a dragon's hoard worth of content for like a full week 😂
Quick correction-it's an OCXO (Oven Controlled, lol). Sorry about that! See you at LTX!
OCCO?
Another potential quip but perhaps was intentional, there was a seemingly intentional use the term "MOST PRECISE" in the video. In the clock world I'd imagine the term "MOST ACCURATE" , used in the title, would have a substantively different meaning than the phrase "MOST PRECISE"
To my non-nerdy audience here: An accurate baseball pitcher consistently throws strikes within the zone, while a precise pitcher can consistently pinpoint specific locations within or around the strike zone.
So you delete comments?
@@ramosel Shills always delete comments. That's how they play the game,
Can you make a video about something that no one really cares about. NVM you just did. Where is the update on ARM processors?
I've gone so far down the rabbit hole of Pi-related acronyms that, for the first few minutes of this video, I forgot what GPS stood for. This is technology at its finest. Love the work you do, Jeff.
lol i use GPS everyday and i forgot . I assumed it stood for "Graphics Processing Sub-System" or something
Stands for Global Pi Synchronization of course
@@InMyElement Hahahaha I thought the same - I was expecting to see Jeff had gotten a 4090’s RayTracing with a Pi4
Yeah, Pi community is huge, they even have their own programming language: Pi-ton.
But some non-believers are trying to mock it calling it python
I put one of these in my microwave's control board and now I can finally test my reflexes stopping the cook time down to the nanosecond like a true action hero.
🍿 I need this! 🔥😲
Truly a Timelord. Can't wait for LTX.
It isn't the high temperature that makes the crystal more precise. It's the fixed temperature.
It's hard to cool components. So this means the oven is used to raise the temperature well above the inside temperature of the device the crystal will be used in.
So assume +50°C ambient temperature, and maybe +75°C inside the device. Then the crystal needs to be heated well above +75°C so no unplanned extra warm day makes the inside of the device warmer than the oven.
After they have decided the oven temperature, they will then cut the crystal to be at the nominal frequency at this temperature.
That's like how wrist watch crystals can be cut to deliver 32768 Hz at close to 37°C from the arm. Don't use the watch and the crystal gets too cold. Leave it in the window and the watch gets too hot. And this makes the watch drift in one or other direction. A 32.768 kHz crystal for a home appliance is better optimized for maybe +23°C. Somewhere slightly above room temperature.
I could've been more clear there :)
But yes, it's easier to maintain a fixed temperature when you heat things up beyond what the typical environmental temperature would be; cooling it would be much more difficult, especially inside enclosures that could vary wildly in temperatures.
One design consideration for anyone using this card is maybe try to keep it out of a stream of heavy airflow, no use making that little SiTime chip work harder than it needs to to maintain its temperature.
@@JeffGeerlingThe opposite of what PC's need I see...
So THIS is why my oven's clock keeps drifting, I always had suspects but now I know
@Imthefake Your oven clock uses actually the grid frequency as a time signal.
@@thebamplayer It's very unusual now to use the mains power AC periods for time. It was quite common 30-40 years ago because crystals was expensive then. And older power supply designs made it easier.
And in that case, at least for my country, you really would hardly see any drift because the frequency might be just below 50Hz during day but then run at just over 50Hz during night to keep a correct total number of cycles over the full 24 hour period.
Just that the removal of old-school mains transformers and instead using switched power supplies means that in modern electronics you now need extra components all the way from the mains-power side. This adds cost - both he components and because of any certification that the mains power is properly isolated.
If you're in an ill-fated submarine headed for the bottom of the ocean, time doesn't really matter. You will forever be the late ill-fated submariner.
Would have been handy to test the time from implosion start to pressure normalization... just few milliseconds.
also good to time how long each job interview was for the engineers of it
it was not fun...
huh?
I love the idea of “I’m not sure if I’ll have a good time, or a bad time, but I’m sure I’ll have a time”
He'll certainly have good time
This is awesome! Looking forward to hyper time-accurate interviews! And a huge thank you for helping raise money for ITDRC. I'm the Florida State Coordinator for the organization and can personally attest to the impact the donations make to help fund our mission. Disasters are never fun, so being able to provide some ounce of hope to the survivors is a true blessing.
Thank you for helping with the ITDRC :)
Hey Jeff, try picking up CHU and WWV and sending them a signal report. They'll send you back a QSL card in the mail. The neat thing about them is not only are they accurate time sources, even their radio transmitter's oscillation is disciplined by their atomic clocks. 73.
I'm going to use WWV as my backup NTP time source in case GPS has any issues in Vancouver!
I would like to contact them soon :)
Isn't wwv specifically designated and intended as both a time and frequency reference? (Which is why the frequency is linked to the atomic clock, otherwise it wouldn't be a good frequency reference)
It's nice to have a super accurate time source but distribution using NTP introduces latency making the accuracy of the source largely irrelevant so what's the point? 😮
@@glennmcgurrin8397 Absolutely. WWV-DO and GPS-DO are both a thing. I wouldn't be able to say how much more accurate one over the other is - but GPS-DO is certainly enough to calibrate SHF ham signals in practice.
@@alanrichardson1672 Using PTP is probably the way to go. It's more precise than NTP
this is the most overkill wristwatch ever created
reminds me of Fred Flintstones wrist watch
Another good example for GPS synched clocks are DAB+ radio stations. For DAB+ you don't use a big transmitter for a large area, like for AM, but a lot of smaller transmitters serving smaller areas. GPS is used to keep all the transmitters synced up.
See ya there! Hope I'm on time...
WOW first time I've been early for one of your videos. You single handedly got me into networking and pis. Thanks!
I like how you make it possible for a mere mortal to somewhat understand all this advanced geek stuff.
I like that too
This is so amazingly/hilariously over engineered….and I love it. While you’ll have the most accurate time there, Linus will still be late. Looking forward to seeing this at LTX!
Maybe they can use it on WAN show to keep it down to under 12 hours ;)
@@JeffGeerlingfor Wan show there is no need for such accurate timing, it just need to be accurate ±2 hours, which means it could be an hourglass with rocks in it 😅
Do you think he measured the draw delay for the screen and put an offset in on the number shown on the display?
For your display… there might be some some signaling and compute delay in your python. Please check your offset calibration, values, and timing. I.e. set a log flag at the start of your script and log flag at the end (or whenever is appropriate) then use that for your screen off-set, and signaling / ptp / ntp offset.
Love the project/product.
I used to have the same job as your dad but in LA ;-)
sandwich? oven? now i am hungry...
Agreed! - "Hey! Hound dog! what's for lunch!?" 🙂
You missed the opportunity to say "This oven isn't forbaking pie's."
ITDRC is a great group. I have worked with several team members on large scale incidents such as wildfires and hurricanes.
I'm so looking forward to all your interviews from LTX. So many of my favorite content creators and fellow needs.
We all have needs hahaha
@@JeffGeerling yea that was a typo autocorrected from nerds loo
Lol
It will take a while even with an oven to age the crystal to a reasonable point of stability, we used to leave ours on soak for 2 months to get them stable enough for broadcast use.
Will you be there on Sunday? Hyped for the convention and hope to see you along with some other tech CZcamsrs I watch
Yes! See you there!
@@JeffGeerling I did see you! Was in line for case toss.
@@benstensaa Ha, one of the highlights of my night! Though my elbow hurts a wee bit now.
@@JeffGeerling definitely hurt my shoulder but got a good score
Very cool project, Jeff!
Hope you have 🕶️
a great time
😎
Lol Jeff I have to say that is such an over the top interview timer. I like your style
I have a Pi Zero running a few little things, including Chrony as my stratum 1 internal NTP, relying on an Adafruit GPS board with PPS. I have a 4x20 screen in an acrylic mount on my desk that serves as my geeky desk clock. It was under $100 all in, and has a few purposes for me.
Just imagine that going through the airport. The TSA and the customs are going to love ya.
I have carried lots of interesting electronics and cables through the customs. The important thing - it doesn't smell like explosives. And it's good to be able to have batteries separated.
Yes; I'll be taking the batteries in a carry-on, while the rest will be packed neatly in my checked bag. I've only gotten taken aside for closer inspection one time carrying all sorts of strange contraptions through security :)
Love these videos. Glad to see you doing better at least on the surface
Just signed up to volunteer with ITDRC!
Awesome! When I was checking on their current deployments, I saw they were helping some tornado victims just south of STL. They're deployed all over the place!
Welcome to the team and thanks for volunteering! Make sure you join the ITDRC slack community so you can keep up with everything goin on here in Region 4 and around the country.
Not there to have a good time, but an ACCURATE time.
With all that python between the time source and the user I'm not sure you can claim the most accurate time, the underlying clock might be the best there but that doesn't do you any good if its displaying late by a probably wildly variable margin (at least in comparison to the clock accuracy). Might be the most drift proof clock present however and so be the most accurate eventually. But it probably isn't delivering the time to the display as accurately as the NTP will be on every other computer there, and even cut off over the duration of the event I'd expect the drift of the riff-raff PC's to be less than the inaccuracy caused by using the wrong language for such a hard realtime task! The most real of real time tasks!
The computer itself will be holding time accurately though-honestly the blinkstick and miniPiTFT are delayed enough even with a C library I'd end up with variable ms-level delays for end-user display.
The Pi will be offering PTP output over Ethernet, though, so I could still say it's the most accurate time source-just not necessarily via it's visual outputs.
@@JeffGeerling True, and even if you went to the extreme of bare metal programming the blinkstick and screen so it is precise as the CPU cycle allow the LED warm up/pixel change times of those HID devices has a meaningful latency when talking this level of timing precision too.
Make sure you serve at least once client with the correct time over the Ethernet as I think you can claim to be the most accurate timesource, but if nothing ever uses the really accurate time it could provide I don't think it counts - the Human interfaces on it are going to be the only things used, and they are not impressively accurate.
@@foldionepapyrus3441 I'll just have to find someone running Linux and using an i225 in their PC, and jack in. Then set up LinuxPTP :D
Love your videos Jeff! Ever since you replied to my comment on a jerryrigeverything video, I've been hooked!!
Glad you enjoy the content :)
It warms my heart to see STL represented at LTX. Have a blast Jeff, can't wait to see all the content in the next coming weeks.
I'm currently syncing Chrony with a stratum 1 server hosted at the Quebec Internet Exchange a few km away, but I'd love to have something like this in my lab!
By the way it's OCXO, the X being short for Xtal/Crystal.
Gah! My brain keeps messing it up lol
CZcams: Jeff Geerling uploaded a new video.
Me: Well it's about time.
1:18 …no, guess the oven is for baking Pi’s… 🙈
Best wishes for your LTX trip! 👍
Linus will show with his personal Cesium Clock.
Good Charity though. Good Luck.
what's linus?
A time card sounds like something you'd whip out at a Yu-Gi-Oh tournament while pushing your glasses back in place.
I used to war drive with my RP4, external GPS and USB WiFi on monitor mode. I captured a WiFi hot spot that was inside a parked cop car, with SSID "Purple Pig". I didn't stop to ask. What's interesting is that your GPS is sandwiched between the CM4 and your PCI board.
Another important difference between the OCXO and the rubidium card is that "board with a chip that gets hot but isn't powered on" is probably a lot easier to clear through customs compared to "board that is radioactive."
Hehe, though any decay in the isotope used in the Time Card (non-mini) would be practically un-detectable by airport security.
They would think it looks a little sus though.
There is no radioactivity in a rubidium clock (unless you count the 50 billion year half life of the Rb-87 used in the filter - but with a half life much longer than the age of the universe, it is debateable whether to call this radioactive). Moreover, the clock shown uses a laser light source, rather than a filtered discharge lamp - so it doesn't even have the Rb87.
thats .005 ppm Marco Reps is gonna love that.
If my time is within 15 minutes, that's good enough for me.
Well it's about time!
Love that St. Louis is being repped at LTX
3:21 Sweet, I'm in a Jeff Geerling video! :D
So excited for LTX and your interviews! This is actually for making sure Linus is on time for the live WAN Show though right?
Can't wait to see it at LTX!
Ayoo, Loved seeing the m8f! Used it in my Bachelor Thesis where I implemented a OCXO (stratum 2 compatible) PLL chip with the PPS Signal coming from the GPS module. They are (even with the internal TCXO) really accurate and low jitter. Iirc somewhat around single digit nanoseconds compared to our big ocxo gps time reference. And yeah, just around 100$ by their own lol
End application was a phasor measurement unit which sampled the grid power based on the PLL output. Gotta keep good time synchronization when you're making the measurements and phasor estimations on the pi. Really great learning experience on how to measure >time
ITDRC reminds me of when I did a presentation at the Akron Linux Users Group on Project Owl. Both are incredible organizations!
This video is just in time 💯
You're literally a magic man, to put it simply
Having involved years ago in buying ntp appliance + Rubidium oscillator for very accurate time, got a kick out of it. To be clear for a majority of users, ntp/chronyc is enough for miliseconds accuracy as Jeff mentioned... unless your doing trading for accurate time.
Timebeat does PTP, NTP, PPS, NMEA and Squared, and it is sooooo much easier to setup than chrony
Time card says time to watch Jeff Geerling!
Just making sure all understand these:
precision: how "finely divided" some measurement is
accuracy: how closely a measurement agrees with some accepted standard
So you can have a clock which has microsecond precision but is off (inaccurate) by minutes. Or you can have a clock that is accurate within milliseconds but only one second precision.
I love the idea of mounting a computer in my computer.
As soon as I saw that Ublox chip I knew it had to be GPS related. I've been trying to research accurate (especially vertically accurate) GPS for a while now and it's pretty hard to understand as a layperson and there's not much info out there anyway, it seems to be a very niche interest. If you could make a video about accurate GPS that'd be so helpful and I think a lot of people would find it cool.
Excellent, I was thinking about running my own time server at home since we live fairly far from any public ones.
Could be a fun project! (And there are certainly cheaper ways of getting GPS signals into your main time server if you want to try that to get started!).
Wel this is neat
This is completely unhinged and I love it
Wow. I discovered your channel because I was doing some Ansible stuff at SiTime.
Oh nice! SiTime makes some neat chips!
Caesium clock and GPS for the win. As an ex calibration technician, that is what I would use.
I could totally see Jake watch this video and decide to 1up you with an atomic clock in their steam cache server lmao.
Haha I wouldn't put it past him!
Very cool! At some point LMG or your self should do a video on AoIP. PTP is huge in that space. Livewire, Wheatnet, Revenna, or Dante would be cool to see a deep dive on!
Not just audio over IP, video is heading in that direction as well with ST2110.
Are you compensating for the processing time and screen response time between the clock and the display? :D
Hehe the annoying thing is the Blinkstick's Python library introduces anywhere between 5-50ms delay, so the LED changes will always be a little off :(
Now I want one of these cards to put in one o f my servers tor replace my pi3 that has a gps hat that is doing the time serving right now. THANKS JEFF
Sitting in the airport to LTX right now!
Hopefully I'll see you there!
Nice video. We used a NavSync timing gps and feed its 10 MHz output to an FPGA and try to derive a 100 MHz signal from gps. This gives a 10 nanosecond pulse period. A cosmic ray signal event in our application is time stamped to 10 nanosecond in theory.
2:56 bro we were chunking out memes while the announcement was happening its too late😂😂😂😂😂😂
We thought we were going to have the most accurate clocks at LTX with ours at .25ppm but .5ppb is unreal. 😅
Oooh... if you have a Dante setup it would be fun to see if I could be the PTP source!
Otherwise, I'll just gawk at your mics for a bit. I was trying to find a good ENG mic to throw in my bag for the livestream.
hope you enjoy it!
Why does "a true second" sound so epic?
Oh yes, I've built a GPSDO before, using an OCXO, a GPS module and part of a PLL chip (specifically the phase comparator). No RPi needed.
(edit) and no fancy hundred-dollars GPS module needed either. A $5 ublox7-compatible module is enough, with some skillful programming of its internal registers. :)
It does depend on what level of precision you are looking for, as well as the quality of your oscillator. My experiments with some of the cheapy ublox devices, show that they can easily show time deviations of +/- 100 ns, meaning that frequency stability at 100 seconds is only 1ppb on average (there can be larger excursions if there is a change in observing conditions).
However, in the event that you need better absolute time precision, or a better precision frequency reference, then improving the GPS receiver may be needed.
One interesting thing about making low cost GPSDOs is that obtaining "well-used" obsolete OCXOs from aliexpress is not just cheap, but the crystals are "pre-aged" and often have extraordinary stability. I've got a bunch of the $2 OSC5A2B OCXOs, and when using these for a GPSDO, the limting factor (by a huge margin) is the GPS receiver - you need to use PLL bandwidths in the order of 200 uHz, otherwise the GPS noise gets through to the output.
I've got a couple of somewhat more expensive, old SC-cut OCXOs from Ali (about $50 each), which when measured significantly outperform the specifications of the rubidium oscillator shown in this video ( < 1x10^-12 adev @ 1000 seconds) with some software temperature compensation. That said, these miniature rubidium oscillators are a lot worse than the older ones. The laser based CPT method used in the miniature versions has much worse stability than the old-school rubidium lamp and microwave excitation design.
Love it - but my ESP32 Stratum 1 NTP Time Server is still going strong! Have fun at LTX!
Is that using a GPS receiver then as well 🤔
@@grahameida7163 yes, a description of the project is on hackaday
Enjoy your time there.😁
Rubidium clocks use the oscillation of the atom between two different excitation states as their clock reference, NOT radioactivity. Rubidium-87, the isotope used in atomic clocks is NOT radioactive.
It’s not for baking cookies, it’s for baking Pi’s!!
The entire video's closed captions are combined into one giant caption at the beginning of the video, then are never seen again.
That shouldn't be the case, but CZcams sometimes does that - a refresh usually fixes it :(
The Xzibit reference was fantastic 😂 cool video!
TIL Hardware Attached on Top, I always thought it was just a cute hat on a pi. :)
Ha! For a time I did too, until I saw someone else write out the full thing on the Pi Forums once.
NTP tested against the 1PPS goes more on the order of 3 .. 10ms and occasionally worse than 10ms.
With the Pi 4, you can test against the Pi clock to about 18 ns resolution. If you take in the 1 PPS and set up an interrupt, then you'll have sub-microsecond accuracy for time - even Jeff should be happy with that?
So - you only need the serial output from the uBlox receiver ($50 - $80 at Sparkfun) breakout board for GPS data and the 1 PPS signal.
I implement this in RTL rather than Linux. Of course this is not within a PC.
If you're using interrupts to capture time then it is likely that you have 10s to hundreds of microseconds of latency and considerable jitter. Linux is not a real time operating system. Interrupt latency varies wildly and is considerably faster in kernel space than user space.
Hardware capture timers are needed for real accuracy.
@@therealtimwarren I'm not using Linux (as stated above). It's a barebones/bare metal set up. Latency and jitter verified against the Pi-4's 54 MHz clock of the system - indeed, with the 1 PPS I can also accurately characterize the 54 Mhz clock''s accuracy as 9 .. 11 PPM (on my Pi) depending on temperature.
Try to get that through airport without sending explosive vibes :D
Pretty much all the use cases listed (banks, remote ground stations, distributed computing) use GPS - namely GPS trained high stability rhibidium for a few weeks of holdover, and GPS trained cesium for anything that needs to operate during WW3. You wouldnt use OCXO for anything where you'd lose your better reference for any ammount of time.
You can use OCXOs for lower cost signal generation while trained to something else.... Like generating a stable multi-mhzs signal off a stable 1 pps. But that stable 1 pps needs to be driven by something with significantly better holdover.
True, but there are many situations where something between a standard TXCO and something a bit more exotic is useful.
@@JeffGeerling The project is fun overkill - just that little bit of the video ran contrary to my industry experience. I agree they have their uses - I've used them myself to save costs - but how this class of oscillator is used (generally) isn't holdover due to lack of comms (which is how I interpreted the video).
@@garretthaney9134 True; and to be honest, I am only dipping my toes in the water of higher-end use cases. I would rely on your opinion more so than mine!
You know that used to be completely true, but there are now “super” OCXOs (made very well with dual oven type designs) that outperform many chip scale atomic clocks…
It's well into the third quarter of 2023 here in Canada and the availability of Raspberry Pi 4 has still not arrived. I still have hope that Upton's promise will come true.
I've seen PiShop.ca getting stock at least a couple times a week lately. Down in the US it's available somewhere at least a couple times a day now, and it'll be in full stock soon.
It's about time! :D
Red Shirt Jeff and Linus Sebastian in the same room??? Mass destruction ahead...
I will *not* bring my 4090. And hopefully this little time contraption will survive a drop or two
The Ublox modules are fairly cheap, They are available on boards for drones. The OCXO is used for the 10MHz output that is used to sync test equipment. Check out Timenuts' if the subject interests you. I have two Meinberg GPS170PCI systems which is a computer card, and a GPS outdoor antenna with a nice molded plastic mounting arm that clamps around a mast, or tower leg.
I have a Vk-172 Ublox 7 USB GPS that plugs into a laptop for field work.
This particular module is $100+ on it's own.
Yeah; U-blox makes a HUGE variety of GPS modules. This high-end one includes the capability for external oscillators and a much better internal TCXO too (100 ppb I think?).
Not to forget the difference between a real u-Blox module and all those cheap Asian u-Blox rip-offs...
instead of 12 v battery pack you can use regular USB PD power bank, regular USB c to c cable and USB PD to 12 v adapter
This is cool Jeff!
What I got from this video: The Apple watch is so bad that you can't use the stopwatch on it, so you applied maximum overengineering and made this? Neat!
I have to use this whole setup for my master thesis and my prof doesn’t even have a budget for it. I’m just settling with NTP implementation and hope it works😅
Not sure it would give a good result at the end for my distributed systems algorithm.
Really cool! Great video!
I'm guessing:
Single
Addon
Module
Wedged
Inside
Card's
Hat
I use IRIG-B to sync my clocks way more accurate than NTP. 👍
So many of my favorite tech creators are all headed to LTX (JayzTwoCents, Sara Dietschy, Jeff, Snazzy, etc). I'm gonna have a dragon's hoard worth of content for like a full week 😂
well... if it's LTT it's probably enough for a month... or two...
Good luck flying with that lol
TSA be like 👀
Please talk about Quantum Compasses! They also rely heavily on clock references.
i love the purple bracelet!
i bet this guy will be the first time traveler
Too soon? Nah, it's already the 2nd boat full of rich people on the same spot...
I want to see a collab with you and ElectroBoom. You should try to interview him at least.
I just want to see if he brings that shock stick with him lol
@@JeffGeerling it looks like he is
"too soon" jinx lol we said it in unison