NTP server frequency stability
Stratum 2+ NTP servers have multiple potential sources of error, let's experiment with lowering them.
Topic
stratum2
A collection of 11 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
TCXO RTC Raspberry Pi Hat
History
I'm bringing my RTC Hats [https://blog.dan.drown.org/tag/stratum2/] back online
(source code [https://github.com/ddrown/stm32-input-capture-f031] and hardware
design [https://github.com/ddrown/stm32-input-capture-f031/tree/master/hardware]
is on github). I originally designed it for frequency synchronization without
phase alignment
[https://blog.
Drift
One of my goals with the RTC Pi Hats [https://blog.dan.drown.org/tag/stratum2/] was to have a
more stable local frequency. This is useful when you can't reach your upstream
clock.
GPS modules lose signal from time to time, especially when your antenna is less
TCXO RTC Hats: aging & RTC frequency
I'm focusing on oscillator aging and RTC frequency in this post. See also:
initial data [https://blog.dan.drown.org/tcxo-rtc-hats-initial-data/], picture
[https://blog.dan.drown.org/tcxo-rtc-hats/], other stratum 2 posts
[https://blog.dan.drown.org/tag/stratum2/]
I've been letting these boards run to
TCXO RTC Hats: Initial data
The TCXO RTC hats [https://blog.dan.drown.org/tcxo-rtc-hats/] are collecting data. I'm
focusing on the RTC part in this post. See also: other stratum 2 posts
[https://blog.dan.drown.org/tag/stratum2/]
Required picture
This hat is on an Odroid C2.
The GPS module on
TCXO RTC Hats
My new stratum 2 NTP server hats arrived from Macrofab today! I have a few hand
soldering things to do (32khz crystal and headers), and then I can start
calibrating them.
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