Dan Drown

mosh on Android

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NTP server frequency stability

Stratum 2+ NTP servers have multiple potential sources of error, let's experiment with lowering them.

Battery backup for fridge, part 2

Continuing from part 1, I run my fridge on battery. Setup To start, I connected the inverter to the battery, first using the 1ohm resister to allow the capacitors to pre-charge then connecting it directly. I'm using a Kill-A-Watt to measure the AC power usage, and a DC

Battery backup for fridge

With the instability with the power grid in the past few years, I wanted to have a plan for how to handle power being out for 24+ hours at a time. For this post, I'll focus on just keeping the fridge running. Goals Fridges are pretty well insulated,

U2F/Fido2 based SSH keys on Windows

When trying to figure out why ssh-agent forwarding wasn't working from Windows to an Ubuntu 22 server, I saw that build V8.9.0.0p1-Beta of Microsoft's OpenSSH port included U2F/Fido2 hardware authenticators. Installing There's a few ways to install this, I'

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.

Adding IPv6 to teensy-ntp

I ported my NTP server [https://blog.dan.drown.org/embedded-ntp-server/] from the stm32f407 to the Teensy 4.1 [https://forum.pjrc.com/threads/61581-Teensy-4-1-NTP-server]. Because I recently switched from a cable modem to fiber, I wanted to use my home stratum 1 NTP servers with my public servers in

Event Loop Software

The simple description of an event loop is a program waits for an external event from many different sources, does some processing on that event, and then waits for the next event. It is a common architecture in many different types of software. This blog post will go into the

AWS Cognito error message "Invalid base64 SAMLResponse"

While debugging why AWS Cognito was giving the error "Invalid base64 SAMLResponse", I didn't see many good answers on the internet. TL;DR - double check your SAML attributes Configuration * My SAML Identity Provider (IdP) is AWS SSO, and I'm using IdP initiated SAML