Dan's notes

I wrote down stuff I ran into

  • Home
  • NTP
  • router
  • android
TCXO

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

  • Dan Drown
4 min read
ntp

TCXO RTC Raspberry Pi Hat

HistoryI'm bringing my RTC Hats back online (source code and hardware design is on github). I originally designed it for frequency synchronization without phase alignment. I was going to write my own program

  • Dan Drown
3 min read

Adding IPv6 to teensy-ntp

I ported my NTP server from the stm32f407 to the Teensy 4.1. Because I recently switched from a cable modem to fiber, I wanted to use my home stratum 1 NTP servers

  • Dan Drown
4 min read

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

  • Dan Drown
3 min read

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 ConfigurationMy SAML Identity Provider

  • Dan Drown
2 min read
kerberos

NFS Readonly Root Filesystem

Setting up a Fedora Readonly Root filesystem via NFS

  • Dan Drown
10 min read
crypto

Cryptanalysis of the Oceantoo cipher

I saw this video of creating an encryption algorithm on the channel Gary Explains: Gary's video goes through creating a new symmetric crypto algorithm. He says multiple times that this is just an

  • Dan Drown
4 min read

2.5 Gigabit ethernet

I've been wanting to upgrade my home network for a few years now.  My home server/NAS can easily fill 1 gigabit, but I also didn't want to spend a lot of money

  • Dan Drown
3 min read
database

Database substring indexes

GoalsImagine you have an application that keeps track of domain names.  And this application has millions of entries in a MySQL database.  How do you efficiently find all domain names that have part

  • Dan Drown
4 min read
kerberos

Kerberos for Windows, without AD

Continuing from the previous post, let's see what Windows can do with a MIT Kerberos based realm. Windows normally uses Kerberos as part of Active Directory, but it does have some basic support

  • Dan Drown
5 min read
kerberos

SSH single-sign on

I was looking for a way to deal with ssh/sudo authentication between multiple clients and multiple devices. I wanted something with a balance between convenience and security.

  • Dan Drown
8 min read
wsl

Mounting a dedicated disk in WSL2

In WSL2, the default disks are virtual. Microsoft has recently added support for mapping physical disks to your WSL2 VM. I was running low on space my C: drive, so I wanted to move some of my WSL2 data to a dedicated Linux drive.

  • Dan Drown
2 min read
bluetooth

Bluetooth Low Energy sensor, part 2

To continue from part 1: I want a wireless sensor that will last more than a month on 2x rechargeable AA or AAA batteries. Some ideas I have for what I could do

  • Dan Drown
1 min read
arduino

Bluetooth Low Energy sensor

I have some ideas for a low power wireless sensor.  I want something that will last more than a month on 2x rechargeable AA or AAA batteries.  I first tried an esp8266 and

  • Dan Drown
4 min read
wsl

Replacing the WSL Kernel

BackstoryI had a dual boot Windows/Fedora machine, and I wanted to be able to run the Fedora install as a VM inside WSL.  To do this, I needed the physical disk accessible

  • Dan Drown
1 min read
teensy

Teensy 4.1 ethernet

I'm a fan of the Teensy line of microcontrollers. I have a whole pile of them for various projects. When I saw that 4.1 was combining a 600MHz processor, 1MB ram, 8MB

  • Dan Drown
3 min read
ntp

Embedded NTP Server

Now that I got the results I wanted from my embedded NTP client, I wanted to convert it to an NTP server.  I also wanted it to support interleaved NTP mode, so it

  • Dan Drown
3 min read
ntp

Embedded NTP client/NTP interleaved mode, part 5

I'll test what happens when I plug my embedded NTP client directly into my NTP servers, bypassing the Ethernet switch.  This ends my long running embedded NTP client series. The systems involvedEmbedded NTP

  • Dan Drown
3 min read
stm32

Embedded NTP client/NTP interleaved mode, part 4

Part 3 ended with an unexplained 3us offset, this post will reduce that. Verifying PTP clock syncI wanted to measure the NTP client's PTP clock sync externally.  The PTP peripheral has the option

  • Dan Drown
4 min read
ntp

STM32MP1 NTP server, part 3

Previous posts: part 1, part 2, NTP client The NTP client confirmed that there was a 943ns difference between my two NTP servers.  Now, to investigate where it is coming from. ChangesI'll start

  • Dan Drown
3 min read
ntp

Embedded NTP client/NTP interleaved mode, part 3

Previous posts: part 1, part 2 In this post, I wrap up my embedded NTP client and use it to measure the difference between my other two NTP servers with hardware timestamps. Goal

  • Dan Drown
5 min read
stm32mp1

STM32MP1 NTP server, part 2

Previous post: https://blog.dan.drown.org/stm32mp1-ntp-server/ I figured out my offset problem, which was not a PLL problem like I thought. Connman has a NTP client enabled by default:(The distro

  • Dan Drown
2 min read
ntp

STM32MP1 NTP server

Previous post: Debian for STM32MP1 NIC Hardware TimestampsFirst step: enable hardware timestamps in chrony.conf: chrony configuration for hardware timestampsNext, enable chrony's measurements log, and verify it's using hardware timestamps (H) not kernel

  • Dan Drown
2 min read
arduino

Wifi NTP server

I saw a thread about someone who wanted a low power NTP stratum 1 server that could run off of batteries and could be put somewhere without an internet connection.  That had me

  • Dan Drown
4 min read
glibc

glibc/Linux DNS Round Robin

A friend was trying to figure out what glibc is doing with DNS round robin, and information about it is somewhat scarce.  He was expecting it to randomly chose an address out of

  • Dan Drown
2 min read
Dan's notes © 2022
Latest Posts Ghost