Dan Drown

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

DOCSIS 3.1 and NTP

Spectrum upgraded my area to DOCSIS 3.1 to offer 1G/40M service. I believe they have it configured for 1.7Gbit shared downstream (using DOCSIS 3.1) and ~100Mbit shared upstream (sharing the legacy DOCSIS 3.0 upstream channels). This is unverified because the modem (a Technicolor TC4400-AM) has

BLE: micro:bit UART

Experimenting with the micro:bit's Bluetooth UART support. This will explore the lower level guts of how Nordic's Bluetooth Low Energy UARTs work. There are tools to make this easier and less full of guts, but they hide the details. Device one: micro:bit, code: https:

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 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

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

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.