Topic

time

A collection of 19 issues

TCXO RTC Raspberry Pi Hat, part 2

The motivation for this project is NTP servers in datacenters - it can be expensive to get a GPS antenna on top of other people's buildings with a wire running down into your rack. The question is, how do you maximize the accuracy of a stratum 2 NTP

APU2 NTP server

I bought an apu2c0. I believe it will make a better NTP server than my other NTP servers.

GPS module measurements, part 3

GPS module comparison: NEO-7N vs NEO-M8N

GPS module measurements, part 2

After the previous tests [https://blog.dan.drown.org/gps-module-measurements/], 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 windowsill. There's something wrong with

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 have on hand is a 72MHz STM32 devboard. I used the input capture hardware on

TCXO aging part 2

The previous data I have on aging [https://blog.dan.drown.org/tcxo-rtc-hats-aging-rtc-frequency/] covered 10 days, and now I want to come back to this now that more time has passed. This data is from the same Pi Hat hardware as that post. The datasheet specification for aging with these

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 [https://blog.dan.drown.org/gps-module-measurements-part-3/]. GPIO PPS is one of the best ways to get that timing

Temperature compensation, part 2

In the last part [https://blog.dan.drown.org/temperature-compensation/], I measured the TCXO to fit a frequency vs temperature curve. Frequency vs Temperature curve Below are the final curves that I went with for the two systems, and a comparison of the median frequency at each temperature point. The

Temperature compensation

Temperature effects are usually the largest source of frequency changes in clocks. So I have three temperature sensors on my test system [https://blog.dan.drown.org/frequency-synchronization-without-phase-in-ntp/]. The sensors are: one built into the stm32 chip, a TMP36 sensor [http://www.analog.com/media/en/technical-documentation/data-sheets/TMP35_36_

Frequency synchronization without phase in NTP

I've been working on my high accuracy RTC project [https://blog.dan.drown.org/stm32f030-devboard-with-tcxo/]. 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 TMP36 sensor is hidden behind a wire