Freedom To Play

Sizing Air Purifiers Using CADR

The air purifier marketplace is an apt metaphor for how a particle must feel while being trapped in a filter - at every turn there's a new acronym or regulatory agency or purifier type. It's enough to make someone buy the first air purifier that looks decent and is in

Removing "Subscribe" from Ghost 4.0

Ghost recently released Ghost 4.0 and with it came a "Subscribe" button and a "Subscribe" footer on every blog post. This does not match the "Just some information on the internet" blogging model of frdmtoplay.com. It is not obvious how to turn these features off, and even when

Patching in Fahrenheit

An interesting no-brand air quality monitor showed up in an Amazon search recently. The sensor is two bare PCBs with an Asair AM2120 temperature & humidity sensor, a SenseAir S8 CO2 sensor, a Plantower PMS5003 PM2.5 sensor, and a 2.8" LED display all sandwiched between two pieces

linux

Self-Hosting Bitwarden without SMTP

Bitwarden provides docker images to self-host an open-source version of the Bitwarden server. After recent updates to the Bitwarden client which broke compatiblity with rubywarden the official image is a viable option despite requiring mssql. However, to unlock Premium features the self-hosted version must have a "verified" e-mail

linux

Running pi-hole on the BeagleBone Black

The Beagle Bone Black comes loaded with a Swiss Army Knife collection of programs that run on boot. NodeRed, Cloud9, SoftAP, nginx, apache2, the list goes on. This is all fine for fresh-out-of-the-box exploration but gets very tedious when trying to extend the BeagleBone's functionality, say by installing pi-hole. Running

openhtf

Automating hardware testing with a Teensy, Firmata, and OpenHTF

OpenHTF ("Open-Source Hardware Testing Framework") is a Python test framework open-sourced by Google at the 2016 Google Test Automation Conference with a big bold disclaimer: "This is not an official Google product", so hopefully OpenHTF cannot be discontinued. OpenHTF is not that different from other task

mysql

Recovering MonicaHQ mysql Database

MonicaHQ released 2.17 for self-hosting and it seemed like a fairly straightforward upgrade (docker-compose pull; docker-compose restart) up until logging into the updated instance presented a gut-wrenching: The whole database is gone! As called out in the release notes, the monica mysql database was backed up, but not backed

kicad

Simulating multi-gate devices in KiCAD with ngspice

Introduction With the release of KiCAD 5, KiCAD supports circuit simulation within eeschema using ngspice. 74HC00 The 74HC00 is a quad 2-input NAND gate. KiCAD splits the IC into five discrete components: four individual gates (Units A-D) and one power unit (Unit E). The experimental ngspice model assumes that each

linux

Self-hosting Bitwarden on a Beagle Bone Black

Password managers are very useful utilities that store (and generate) unique and lengthy passwords. Many utilities exist to store passwords locally (pass, EncryptionWizard, etc), but I need my passwords synced across several devices. Dozens of password managers exist that perform multi-device sync. But, many services require storing passwords on their

python

Maximizing Bugs Bunny

There are dozens of Looney Tunes DVDs and Blu-Rays for sale. Warner Bros has released four "Collections" that contain some unique episodes but contain a majority of dupliates. Some individual compendiums are 100% duplicates of existing sets, while some have unique episodes. Unfortunately, Warner Bros hasn't provided a

linux

Virtualizing Windows 7 (or Linux) on a NVMe drive with VFIO

VFIO (Virtual Function I/O) allows PCI devices to be passed directly from the host operating system to virtualized guests. Normally, PCI passthrough is used to get neat native performance from graphics cards. Passthrough can also be used with NVMe drives, which use a PCI lane, to get near native

linux

Using ddccontrol as a non-root user

Most modern computer monitors support Display Data Channel which allows the screen brightness/contrast/input to be changed without using the on screen display. Many DDC implementations "just work" over HDMI, DisplayPort, or DVI by creating an i2c interface. Some monitors, like Dell Ultrasharps, also expose a DDC/

linux

Gigabyte Front Panel Audio with Linux

On some Gigabyte motherboards (including the Gigabyte Gaming 5) there are issues with front panel audio not playing. Speakers plugged directly into the motherboard are detected by Linux and play audio as expected. Front panel speaker connections appear in Volume Managers as expected but no sound is played. A look

linux

AMD RAID on Ryzen

Warning : This guide is not for the faint of heart. Backup data before proceeding. Here be dragons. This process involves a) compiling a kernel b) compiling a kernel driver c) adding that driver to the kernel d) creating a new LiveUSB installer containing the custom kernel+driver. Here be dragons.

linux

Counting wireless devices on a Raspberry Pi with tcpdump

I was recently a vendor at a large conference and was tasked with keeping track of how many interactions we had at the booth. Rather than use a tedious mechanical clicker to count guests, I set out to create an automated method. Luckily, it was safe to assume most of

Configuring a VLAN per SSID with OpenWRT and pfSense

Architecture Overview My current network setup uses pfSense as the firewall and DHCP server with OpenWRT running on a TL-WA801ND wireless access point. OpenWRT broadcasts two SSIDs which reside on two different VLANs. After a power outage my pfSense box was caught in an endless reboot cycle. I very quickly

ledger

Using python to plot ledger transactions

ledger is a very capable piece of software for double-entry accounting. However, it only provides one out-of-the-box option for visualizing transactions: gnuplot. Rather than learn a non-FOSS tool (gnuplot is not really GNU), I set out to get ledger transactions into pandas. ledger includes python bindings which worked for 95%

Nest Thermostat v3 Teardown

Quick and Dirty Look at the PCB Work in progress, complements the FCC Application Screen Side Freescale MCIMX6X3EVK10AB Data Sheet 6TDID NW189 Micron NAND mt29f4g08abbdah4 Freescale SMPF0200 51AEP KEPFTG Potentially NXP MMPF0200 power management IC ELPIDA B443268PA-1D-F 4Gb RAM 16430R01200 STM32L 151VCH6 78A2T V6 Probably LCD Driver? EM3581 1652A00MQL Zigbee

linux

Kali Linux on the BeagleBone Green Wireless

Some bad news Unfortunately, the BeagleBone Green Wireless uses the Texas Instrument WL1835 which does not support monitor mode. The BeagleBone Green Wireless cannot be used with airodump-ng, kismet, tcpdump, etc. out of the box. Fortunately, the BBGW has USB ports; therefore, USB Wi-Fi dongles can be added for promiscuous

On a Researcher's Momentum

One day a coworker casually claimed "As a researcher you have a fixed momentum: if the number of projects you have lowers then you're able to work faster". This is an exploration of his claim. Every researcher has a fixed momentum First, the momentum of a particle: $$p

linux

i3, udev, & xrandr: Hotplugging & Output Switching

One of the benefits of using a Desktop Environment (DE) like Gnome or KDE is that a lot of "user friendly" things are automagically taken care of. With i3, a minimalist Window Manager, that is not the case. One of the more convenient things missing from a default

Using curl with the Amazon Product Request API

Motivation Amazon provides a handy Product Advertising API that allows you to fetch the price, reviews, description, and image (among other things) for products. There are several examples on how to use the API for Ruby, PHP, Python, and Java. But sometimes it's useful to use curl from the shell.

ledger

Envelope Budgeting with ledger

To fully appreciate this tutorial, a rudimentary understanding of ledger, double-entry accounting, and envelope budgeting will be necessary. The Goal: An envelope budgeting system similar to YNAB Envelopes that "roll-over" and don't reset monthly Have budgeted items tied to real accounts, ie. rent money comes out of Checking

linux

Nehalem CPU Power State

Recently I re-installed Arch Linux after a several year hiatus. One of the hiccups in coming back was that I'm no longer running the latest and greatest hardware. My CPU (Nehalem) is power managed with the acpi_cpufreq module while the latest and greatest processors are using a new p-states

mbed

Using mbed with Kinetis Design Studio

A brief overview of the process for building mbed projects with Kinetis Design Studio Install the necessary tools Modify the mbed toolchain to support KDS 2a) Modify the mbed source code to be more KDS/K64F friendly Build the mbed core library Build a sample mbed project Import the mbed