ntp APU2 NTP server I bought an apu2c0. I believe it will make a better NTP server than my other NTP servers.
ntp RK3328 based NTP server I got a ROC-RK3328-CC SBC because it has true gigabit ethernet, emmc, and USB3. These are all better I/O options than the latest Raspberry Pi 3 B+. I put a SATA hard
gps GPS module measurements, part 2 After the previous tests, I ordered another GPS antenna to improve the signal conditions. They're just the cheap puck style antennas with SMA connectors ($10 on Amazon), and I've put them on my
gps GPS module measurements Starting point I got a u-blox NEO-6M and I wanted to compare it to my NS-T. Since I don't have a frequency counter, I decided to try creating one myself. The hardware I
ntp PPS over USB Goal For keeping your system clock on time, you can't beat the Pulse Per Second (PPS) signals available from $10 GPS modules. They typically have better than 100 nanosecond accuracy. GPIO PPS is
time Frequency synchronization without phase in NTP I've been working on my high accuracy RTC project. Here's a picture of one of the two systems: Connections The TCXO devboard, BME280, and PCF RTC are all on the i2c bus. The
rtc RTC comparison Real Time Clocks I bought two high accuracy RTC (real time clock) modules and wanted to compare them. RTCs are useful for very low power clocks. They can run for years off of
ntp GPS PPS drift when it has no signal Question: What happens to a GPS receiver's pulse per second (PPS) when it loses signal for a long time? To answer this, I first moved the antenna away from the window and put
gps Beaglebone Cape for NS-T, revision 2 I'm testing the second revision of this cape now. Schematic is on github (left: rev1, right: rev2) It's working much better than rev1, but time will tell if it has the same frequency
gps Update on Beaglebone Cape for Navspark NS-T The cape has been running for 5 days now. I've been tweaking the system to see if I can get it stable. So far, the local clock looks like this: The red line
navspark Beaglebone Cape for Navspark NS-T Goal My next goal in the quest for a better NTP server is to improve the TCLKIN source. Previously, I was experimenting with TCXO's. I bought a Navspark NS-T (a timing-grade GPS receiver)
gps TCXO + Beaglebone Black, part 2 Starting from the previous TCXO modification, I wanted to get a 24MHz TCXO working. Trial #1 I bought a set of three undocumented 24MHz TCXO's off ebay for $6. I was hoping that
navspark TCXO + Beaglebone Black I've added support for an external clock (TCLKIN) to the Beaglebone Black timer driver. Setup I used what I had on hand to test it. I setup a Navspark microcontroller to send a
gps Beaglebone Black timer capture driver More info on: Hardware, Kernel Driver software The Beaglebone Black has a hardware timer capture. This means it can save the couter value at the time an input edge happens. Since it has
gps Beaglebone Black GPS+Temperature cape I moved my Beaglebone Black GPS+Temperature setup from a breadboard to a proto cape. The soldering isn't great, and the wire I had on had was much too thick for this. The
gps Beaglebone Black NTP/GPS Server, Temperature Compensation part 2 See the Part 1 of Temperature Compensation or the hardware setup Overview In part 1, I did a trial run of chrony's temperature compensation and got a pretty good result. In this part,
gps Beaglebone Black NTP/GPS Server, Temperature Compensation part 1 See also: The hardware/software setup or part 2 Overview Chrony (the NTP server software) has temperature compensation built in, using a quadratic forumla to estimate the effect of temperature changes have on
gps Beaglebone Black NTP/GPS server Goals I wanted to experiment with using temperature measurement to augment a NTP stratum 1 server. I started with a very similiar setup to this one. [Edit: the8thlayerof.net is gone, link changed
gps Stratum 2 NTP over a Cable Modem Goals I have a Stratum 1 NTP server at home, and ideally I'd like to join the ntp pool as a server. The problem is, my home connection isn't up to this task.
navspark Measuring Asymmetric latency via NTP, part 3 Part 1, Part 2 Varying round trip times Asymmetric latency changes NTP's calculated clock offsets. What do the offsets look like when two clocks are in sync (or always within ~200us) and the
navspark Measuring Asymmetric latency via NTP, part 2 See the first part for the math Let's use a third party (stratum 2) observer to compare the stratum 1 NTP clocks. Round trip times First, a graph of the $rtt times from
navspark Measuring Asymmetric latency via NTP Goal Learn more about the latency characteristics of my cable connection. Starting point I have a stratum 1 NTP server at home. Below is a graph of its performance. The offset between the
navspark Navspark NTP stratum 0 clock Project Goal I want to create a stratum 0 NTP clock that does not require soldering or any special hardware. It should only require a USB port and software. It should have at
arduino Navspark UART/USB bridge I created a program on the Navspark to send characters at 150 microsecond intervals and then received them on a PC. Below is a histogram of how long it took between characters: The