Dan Drown

NIC interrupt coalesce impact on NTP

I noticed that my Odroid C2 system had a much higher round-trip time than I had expected. It has a gigabit ethernet built into the CPU, so it should be decent. rtt min/avg/max/mdev = 0.577/0.605/0.627/0.020 ms (10x ICMP pings) To compare

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

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 a coin cell battery. Both of these modules are special in they claim higher accuracy than your

Turris Omnia

My Turris Omnia arrived today! LED colors based on Network Traffic Video of it in action: https://youtu.be/bMkGp54xWqQ Forum post: https://forum.turris.cz/t/led-color-based-on-bandwidth-usage/1262 Blinky Lights The RGB LEDs can be controlled by sysfs, the "A" and "B" ones are available

stm32f030 devboard with TCXO

I'm interested in making a high accuracy real time clock (RTC). To experiment with the hardware I need for that, I created a development board based on the STM32F030F4P6 (which is a 20-TSSOP package) and a TCXO. I chose that STM32 for two reasons: one, because it'

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 it in an anti-static bag. I did this on the 16th at 01:02 GMT.

Getting Fedora Server running on the Utilite Standard

I installed the Fedora ARM Server image on a Utilite Standard [http://utilite-computer.com/web/utilite-models] (which is based on a dual-core Freescale iMX6 1GHz). Not everything is working, but these are my notes. download the Fedora ARM Server image from https://arm.fedoraproject.org/ There are installation instructions at

Binary Clock, Update 3

I've made some progress on my binary clock project Here's a video of it in its new case: https://www.youtube.com/watch?v=VnHRYwOf2ZQ I've been tweaking the clock controller code and experimenting with different setups to see how the code reacts. First