Dan Drown

GNUK: Open Source GPG/SSH hardware key storage

I noticed the GNUK project had support for the STM32 Blue Pill. I've been looking for an open source hardware key storage for GPG/SSH keys, so I tried it out. GNUK supports the OpenPGP smartcard protocol, and has space for 3 keys. The keys are named: "

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.

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'