I just wanted to say, this is a really great youtube channel. Keep it up!

I recommend getting a GPS module with a PPS (pulse per second) wired pin. Almost ublox chips have a PPS, you just need to get a pre-built module with one. Just make sure use pin one for the PPS timing. (Yes, you have to use the voltage stepper. I am using a Garmin GPS 18x lvc. With the 18x lvc I didn't need a voltage stepper due to it already set for 5V.

Very interesting, watching you taking PFSense to that level of accuracy. You're blessed with creativity. Thanks alot!

Really informative video, Mark!

This brings back so many memories of working with RS232 and 449. You pretty much described synchronized data transmission. Very interesting but shielded twisted pair cable would have cut down on any cross over noise. Yeah I know it can be expensive. If you continue to do more work with RS232 I would suggest a break out box with jumpers to help troubleshoot without the need to rip everything apart. Oh and it would have really been interesting if you had shown both transmitted data and the pulse together on the scope so we could see them line up. Great Video...

Please do a video on USB, I would love it. I really enjoy they way you explain things.

Hi Mark, just for your informatio, MAX3232 has two channels,by default one RS232_to_TTL adaptor only use one of them.You can actually wire PPS to another channel. MAX actually can handle power range from 3.3 to 5.5v, So you can directly use USB's power source. Inspired by your idea, I used one adaptor and cut one of serial port to to deliver USB 5V to ethernet cable, powered them up directly. Next step I will design a circuit board to attach them all together.

Nice video, Mark! I like it very much and it helped me a lot to understand how a GPS-locked time reference works exactly. Although, I was thinking about what you said about USB being a possible jitter "inducer" if it's used instead of a RS232. RS232 operates on a much lower speed and, thus, introducing latency as well. But that latency can be predictable since the speed is constant on RS232 and it's not a shared media. I would like to see the same graph measurement with a USB-RS232 adapter used instead of a direct RS232 connection. High-speed USB2.0 devices should be polled by the USB host every 125 microseconds and that is probably enough to keep the time reference and ntp time on the PC accurate within 1ms. At least, that's what I think... Thank you again! Keep up the good work, man! BTW, is that a Cacti generated graph? :)

I was wondering if you still have your list of references you used to research this. I loved your video and I want to binge on this subject. When you reference location vs time gps are you referring to dual frequency gps? I now need to look into see if an Intel NUC has serial on it. You referenced there are better serial devices to use for this. What attributes should I be looking for, just a secondary data pin? Could you not build this ontop of a RPi, use it as the NTP server, and run DIY PoE out to the device?

In LOOONG retrospect, would it have been easier to use a long five conductor cable to feed power and pull signals from the GPS module, fitted it in a small box, and run wires back to your level shifter module near the PC? Using an old S-Video cable comes to mind as you have 4 conductors and a shield that can carry ground. ;)

So if I need the Data on my Arduino, can I connect the GPS thing directly to the Arduino? I want to make a GPS LED clock is this even possible with this kind of setup? (Arduino + this GPS Module)

Would have been nice to include a parts list and possibly links in your description. Even better would to also have a link to a schematic.

I'll bet that serial cable came with your UPS and is wired crazy to put various status info from the UPS on various RS-232 status signals. I think the choice of "Invert Pulse" or not is important, depending on which edge of the DCD transition the interrupt fires on. Otherwise, your 1PPS signal will be off the width of the pulse. Perhaps the 1PPS driver in FreeBSD can be configured to use either edge? Very nice work, I'd like to eventually do something like this with my pfSense box.. I did some work back in the FreeBSD 4.x days with a custom "time and frequency processor" board that had a disciplined oscillator (either by GPS or IRIG-B timecode). You could get the current time to 100ns resolution with a couple of PCI bus accesses (with the time latched on the first read cycle.) It also had the ability to generate an interrupt at a programmed time, and it made an interesting platform to measure interrupt service time latency. I think its improved quite a bit since the days of the 266MHz Pentium, but interrupt service time jitter was much worse when the ATA disk driver was busy.. This was part of some work to do precise one-way network latency measurements over an ISP backbone, and eventually led to getting the SO_TIMESTAMP code I wrote into FreeBSD (and later other OS platforms) and the corresponding code in NTP. Extreme NTP time synch stuff is a sickness, but so much fun!

My pfsense machine lacks serial. would one of those really expensive mini pcie cards do the trick or would that also suffer weird latency similar to usb? Another thing I noticed is those cards had a 4 pin molex cable for 5 or 12 volts. Is that actually needed for this project?

Except for the profanity this is a superb video. I enjoyed watching your journey to a good time source. Be careful though or you'll turn into a time nut and start comparing different GPS unit stability, then you'll end up getting your own cesium standard. 😆

You said that the resolution of this location gps (vs time gps) is good enough... How good is it? I’m trying to sync 2 or more computers accurate to +/- 1ms.

unaware of how much voltage sag there is with intermittent power consumption but it would be simple to nearly eliminate with a small capacitor to ground at the end of the power wires.

dude you are crazy smart. how did you learn to do all of this?

This video has put me to sleep both times I tried to watch it. I think I need more coffee.

Could that of been a UPS serial cable? I know my old rackmount APC didn't works unless I had the "special" cable. This looks like a nice project and may have to give it a try. Is the maps section enabled only because it's a local?

Might be interesting to do a revisit - timing-grade GNSS receivers (multi-constellation "GPS") are under $100 now... And, one can do a local 10MHz ovenized oscillator to generate the 1PPS tick - then use the GPS 1PPS to steer the local oscillator. Also would have been better (IMHO) to do some RS-485 conversion for the TX and 1PPS signals over Cat-5, using the remaining two pairs for power+ground.

This shows the stability change after the installation: imgur.com/dbOTsic

can you convert the uart to ethernet?.... and if so is Ethernet appropriate for timing NTP?

Sounds like a null modem serial cable.

Nice video!I am not entirely sure if the problem with the weird Serial cable was already addressed in a comment, but I believe the cable you've got there is an Null Modem Cable. en.m.wikipedia.org/wiki/Null_modemSincerely SN

What was the other more expensive GPS board you looked at ? Can you make a GPS that plugs into the RJ-45 Ethernet Lan Port ? And you do plug into the Lan and not the Wan Port ? Thank you for the video ! tjl

would this setup render the result as an official stratum 1 server, or does the fact that you didn't use the "time GPS" module disqualify it for that?

I have the Neo-6M and if I put 5 volts to vcc, the regulator gets hot

could you not have just run the program with wine?

And why is this time so important? Oh! and what camera do you use for recording?

For what reason do you need time this accurate vs using a time server on the Internet

"NTP will shit the bed". Nice :P

If you put MercuroClear on that left index finger nail (right corner) before you go to bed at night it heals much faster.

맞네아들

Aah haha yes... lose pps and all DOES shit the bed. Good times...

take deeznutz :D

Why do you need a second accurate time on your router. Like what are you doing that you need that accuracy? It's a cool project but a time server should suffice right. Haha I wasnt allowed to have internet on my computer as a kid when the 56k was a big deal. So I ran a coaxial cable from the phone wall socket to my room and plugged it in my computer😂 gave my parents huge bills tho😅 But for the love of electronics please use a freaking RJ45 connector to hook it up! 🤦‍♂️