Avatar of Daniel James a.k.a. thzinc

I’m Daniel James. I write things here when I feel like it. Find me on the fediverse (Mastodon, et al.), Twitter, GitHub, LinkedIn, or a myriad of other sites.

Newest Posts

A1 Reference Style Spreadsheet Column Names - Interview question of the week from rendezvous with cassidoo

Nice little brain teaser involving number base conversion 😄

missingBits - Interview question of the week from rendezvous with cassidoo

Nice, bite-sized algorithm question.

Spin the Wheel - Interview question of the week from rendezvous with cassidoo

Well, I spent quite a bit more time on this tonight than I’d originally anticipated. It’s not pretty, but it does work and has a little bit of viable game theory.

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Making candles with 3D-printed molds

My wife has been enjoying making anise, cinnamon, and citrus water centerpieces with floating tea lights. They look pretty on the table and they smell nice without setting off my scent allergies. But after a few weeks, we started accumulating spent candles. I started to wonder if I could melt...

sumEveryOther - Interview question of the week from rendezvous with cassidoo

This was a fun, light interview question this week.

Updated Flipper Zero CO2 Monitor

Well, I finally got around to updating my CO2 Monitor to take advantage of the latest APIs in the Flipper Zero firmware. (It wasn’t quite as bad as I thought it would be 😅) Now it even has its own application icon!

Fidget switch on a whim

On a whim, after someone on a Discord server shared a video of a fidget switch they printed, I decided to try a quick interpretation of the design with the materials I had on hand.

Cardboard stock sorting shelf – design and build

I was in the mood to build something with my hands, and I have been working on getting my garage organized into a functional space to do all sorts of maker-y things. I have a strong tendency to “collect” various materials that I think will be useful eventually. In order...

Guidelines for backlog refinement sessions

Formerly referred to as “backlog grooming,” backlog refinement is the process of defining pieces of work and estimating the amount of effort required to complete them. Backlog refinement requires buy-in from developers, testers, and stakeholders (product managers, business folks, etc.). Doing this refinement work results in a clearer understanding of...

rectangleSum - Interview question of the week from rendezvous with cassidoo

This one was tricky to stay mindful of the number of iterations.

Manually calibrating the Sensiron SCD30 CO2 gas concentration sensor

I picked up an Aranet4 Home CO2 sensor on a Black Friday sale and have finally had the chance to run a commercially-calibrated CO2 sensor against my DIY CO2 monitor on the Flipper Zero and found that my sensor needed some calibration.

verticalSlashes - Interview question of the week from rendezvous with cassidoo

I do enjoy getting Cassidy’s newsletter late Sunday/early Monday and trying my hand at the “interview [questions] of the week.”

Paint fume extractor adapter for shop vacuum

Recently, I designed and printed a battery box to power some new lights on my bike. The box is pretty great and feels reasonably study, but I wanted to give it a bit more of a protective coating to avoid friction from pulling the printed layers apart. I decided to...

How working on Developer Experience (DX) improved knowledge sharing and enabled more developers to contribute to a project

A four-year old Android app installed on thousands of transit buses needed some serious improvements to usability and reliability. The product team proposed a bold vision for improving the user experience for bus operators, but the development team was mired in a codebase that was hard to understand, difficult to...

Writing software that works with hardware

I’ve been working on a lot of hardware projects lately: making text-to-speech appliances work on transit vehicles, making software for internet-connected signs, prototyping tools to help me make good health decisions, and building out my go-sensors libraries to support physical environment sensors. I’ve spent a lot of my time as...

A story about protocols and documentation

In April 2021, I had a problem at work: I didn’t understand how our on-vehicle application communicated with the text-to-speech appliance to make next stop announcements.

Prototyping a real CO2 monitor on the Flipper Zero

Updated January, 12, 2023

Prototyping a volatile organic compound (VOC) and CO2 monitor on the Flipper Zero

I’ve been playing with environment sensors for a while to help me understand how factors of air quality correlate to my health. In 2019, I had a particularly bad asthma attack that was exacerbated by wildfires in California. Since then, I’ve learned a lot about how 2.5 micron particulate matter...

Why we support World Central Kitchen and Equality Texas

I’m so grateful for friends and family celebrating with Bonnie and me. When Bonnie pitched the idea of fundraising for our 15th anniversary, I was excited. She’s got a keen sense of knowing what good needs to be done and who’s engaged in doing that work.

Bonnie and Daniel's 15th Anniversary

Friends, it’s a weird and wild time to be alive. There’s a lot of bad stuff going on, but also some good! The inexorable passage of time has inexorably passed, and with it, Bonnie and I are celebrating 15 years of marriage in 15 days, and we’d like for you...

My first year with a 3D printer

It’s been a full year since I bought my Sovol SV02 printer. I’m sitting at my desk with at least a dozen printed objects around me: fidget toys, small art pieces, organization trays, and electronics enclosures. The process of learning about modeling, manufacturing, and materials science has been fascinating (and...

Using Excel to make changes to GTFS feeds

In my work at GMV, I’ve had need to inspect and edit General Transit Feed Specification (GTFS) feeds on numerous occasions. A GTFS static feed is simply a ZIP file containing several CSV-formatted text files that describe the routes and schedules of a transit agency. Because GTFS is a specification...

Interviewed for "How to plan smarter for event-driven architecture design"

I was interviewed by my friend and author, Bob Reselman on the topic of designing systems with event-driven architecture (EDA). His article–which includes a great primer on how to think in terms of events–is published at RedHat’s Enable Architect.

New housing for RadioShack 22-810 15-Range Digital Multimeter

I was tired of fiddling with the fold-up case that my RadioShack 22-810 multimeter (photo not mine) came in. The probes were a pain to fit into the case properly and I also wanted to have the option to use wires with Dupont connectors to play nicely with my breadboard....

mRNA Vaccine Visualization (and cute frame for my vaccination record card)

I grew up with my mom telling me stories about chicken pox, and then a few of my friends caught it. I avoided catching the pox and I was able to be vaccinated against it. Now I’m an adult with a significant protection against shingles! I think vaccines are fantastic...

How I turned my Levoit Core 300 air purifier into a fume extractor

For multiple reasons–my asthma, air quality, and COVID-19–I run several air purifiers throughout my home. I run a whole Levoit Core 300 air purifier on top of my desk, which typically is useful for collecting my cat’s dander in addition to putting clean air out close to my face. However,...

I tried to make a watering device for my cat

My cat has an addiction to drinking directly from the tub’s faucet. We’ve tried to get him nice water dishes and electric pump water fountains, but he just craves that good, good tub water. (And is extremely vocal about when he wants to drink.)

Harmony Aikido Foundation website launch!

Harmony Aikido Foundation is a nonprofit dedicated to teaching self defense to women and girls. I got involved with the nonprofit after my friend JT Tam recruited my wife and then me to join in his vision to help women defend themselves against acts of violence. Our work needed a...

How I Built a Twitter Bot Using Auth0 Webtasks and Data.gov

I wanted to build something small, fun, and socially-engaging. I have been following Darius Kazemi (@TinySubversions) and the community of bot makers at Botwiki (@Botwikidotorg), and I decided a Twitter bot was the way to go. I have also been following the US Executive Order 13792 pretty closely. The order...

MQTT, Mono, and ARM

I wrote a .NET program to test building and cross-compiling an application to run on a Sierra Wireless AirLink RV50 gateway.

Think LINQ – .SequenceEqual()

Up until March 26, I had come up with a number of crazy concoctions to test whether one IEnumerable<> was equal to another. Some of them chained together .Intersect() with .Count(), comparing the count of the elements in the intersected set with the count of the elements in each of...

Think LINQ – .Skip() and .Take()

Needing to page through a collection is nothing new, and LINQ handles this nicely with two different methods: .Skip() and .Take(). The .Skip() method will skip over a specified number of items in an IEnumerable<>. The .Take() method will iterate over a specified number of items of an IEnumerable<> and...

Think LINQ – .Any() and .All()

“I just want to know if there’s anything in this List.” “Do any of the strings in my array start with ‘q’?” “How can I be sure all of the Rectangles in my IEnumerable<> have a width of 10?” These are the types of questions .Any() and .All() can answer....

Think LINQ – .SelectMany()

I recently came across a beautiful example of .SelectMany() used to find all types that implement a particular interface in all currently loaded assemblies. With minor alterations, here is how I used it:

Think LINQ – .ToLookup()

There is an class in the .NET generic collection framework that is often overlooked: Lookup<>. In effect, a Lookup<> functions like a Dictionary<> whose value is an IEnumerable<>. Though Lookup<T,U> is an implementation of IEnumerable<IGrouping<T, U>>, it functions with a similar efficiency to Dictionary<T,IEnumerable<U>>. Part of the LINQ extension methods...

Think LINQ – .ToDictionary()

There are a number of reasons to use Dictionary<> objects. Aside from the obvious name-value pair uses, Dictionary<> can also be used to essentially “index” an IEnumerable<> of objects. In testing with my colleague, Ryan Davis, we found that for IEnumerable<> collections that we intended to search through on a...

Think LINQ – .Cast()

Personally, I find that .Cast() is an often overlooked part of LINQ. Of course, .Cast() is handy when casting each element of an IEnumerable<> from one type to another. However, one detail in its method signature brings to light a much more interesting use: .Cast() extends IEnumerable, the non-generic interface,...

Think LINQ – The Wonder of IEnumerable<>

Language INtegrated Query, or LINQ, is a .NET feature that makes possible a powerful and extensible query on objects and collections thereof. LINQ is really a combination of a few key components: extension methods and generic collections. Understanding these two key components makes it much easier to “Think LINQ” when...

What's Green, 24/7, and Just Plain Cool? – VMWorld 2008 breakout session

Breakout session at VMworld 2008 in Las Vegas, NV about VMware Server and its role in Raideil’s fully virtualized infrastructure. I presented this session with my two partners, Kraig van der Klomp and Yves Accad. This was my first speaking engagement and it was a thrill to deliver this talk...