cdwilson.dev

I bet you can't RE this receipt

Wed, 21 Jan 2026 00:00:00 +0000

I will send $100 to the first person who can reverse engineer how Target calculated the $162.10 total amount on this receipt.

This is not a joke. I’m totally serious.

Rules Link to heading

The first person to build me a spreadsheet showing exactly how the $162.10 total amount is calculated (step-by-step with explanation, including how to calculate the $64.67 taxable amount in the red box), will be sent $100 via Venmo, PayPal, etc.

Hackaday Supercon 2024

Thu, 07 Nov 2024 00:00:00 +0000

I finally got a chance to sit down and reflect on this past weekend at Hackaday Supercon 2024.

You might expect that a post about Supercon would be all about epic badge hacks, or a recap of interesting talks, or photos of the (surprisingly good for a conference) food that I ate 🌮

But what I really want to do is tell you a story of how the kindness and generosity of a bunch of random people made my first Supercon… well… SuperFUN!

2024 mid-year update

Wed, 26 Jun 2024 00:00:00 +0000

It’s been a little while since I’ve posted anything new here, but that doesn’t mean I’ve been resting on my laurels!

Here’s what (and where) I’ve been writing recently 👨🏻‍💻

Content for clients Link to heading

Over the last year, I’ve been doing some Zephyr-related technical writing for the Golioth blog.

You can see the full list of articles I’ve contributed at https://blog.golioth.io/author/cdwilson/

Common Ground Electronics Link to heading

In addition to authoring technical content for clients, I’m also starting to write about embedded systems and IoT-related topics on the Common Ground Electronics blog. So far, I’ve written about how to enforce Zephyr code quality with pre-commit and my experience prototyping a WiFi serial logger with Golioth. I also just posted a mid-year retrospective where I talk about how the business was started and what I’ve been working on over the last year.

A better difftool for KiCad

Mon, 06 Feb 2023 00:00:00 +0000

It can be difficult to tell what has actually changed when running git difftool on a .kicad_pcb file because KiCad embeds timestamps into the file that change when the file is modified:

Luckly, we can tell git to use a custom difftool using the --tool=<tool> argument.

First, we need to create a custom shell script to pass to git difftool --tool=<tool>. I use Kaleidoscope.app as my git difftool on macOS, so I named this script kicad-ksdiff and put it a directory on my $PATH:

KiCad database libraries on macOS

Wed, 14 Dec 2022 00:00:00 +0000

Info

On December 11, 2022 the KiCad team announced support for macOS universal builds in the 6.99 nightly releases. Using a universal build greatly simplifies the process of setting up database libraries and is strongly recommended. If you are using an older x86_64 nightly build released before December 12, 2022 on a Mac with Apple Silicon (i.e. the file does NOT start with kicad-unified-universal), make sure to follow the old instructions found here:

Set KICAD_DOCUMENTS_HOME on macOS

Tue, 06 Dec 2022 00:00:00 +0000

KiCad Documents Home Link to heading

KiCad 6.x introduced the concept of the “KiCad Documents Home” base directory, described as the:

Base path of KiCad user-modifiable documents, such as projects, templates, Python scripts, libraries, etc. Subdirectories will be created within this directory for each KiCad minor version. This directory is provided as a suggested user data location, but does not need to be used.

By default, KiCad creates this folder in ~/Documents/KiCad/:

KiCad database libraries on Apple Silicon

Fri, 04 Nov 2022 00:00:00 +0000

Warning

On December 11, 2022 the KiCad team announced support for macOS universal builds in the 6.99 nightly releases. Using a universal build greatly simplifies the process of setting up database libraries and is strongly recommended. If you are using a universal nightly build released after December 12, 2022 (the file starts with kicad-unified-universal), make sure to follow the updated instructions found here:

https://cdwilson.dev/articles/kicad-database-libraries-on-macos/

Overview Link to heading

A new “Database Libraries” feature was recently added to the KiCad macOS Nightlies (6.99) and is scheduled to be officially released in KiCad 7. Here’s an overview from the documentation:

40% keymap for Keyboardio Model 100

Sun, 30 Oct 2022 00:00:00 +0000

After backing the wildly successful Keyboardio Model 100 Kickstarter campaign last year, I finally received my keyboard in the mail 🥳

The keyboard is ✨beautiful✨ and the custom-sculpted keycaps feel really great to type on. After using the Model 100 for a couple weeks now, I’ve finally settled on a 40%-ish (3 rows of keys) keymap that feels really natural for me.

Although this keymap works really well for me personally, it’s probably not the right keymap for everyone. The Model 100 is a roughly 60%-ish (4 rows of keys) keyboard, so it may seem odd that I’m only using 44 of the 64 available keys on the keyboard. I thought it might be interesting to walk through my thought process step-by-step and discuss some of the requirements that drove the decisions about where to map each key.

USB over IP with VirtualHere

Tue, 05 Jul 2022 00:00:00 +0000

Raise your hand if you’re tired of having a spaghetti mess of USB hubs and dongles hanging off your laptop? 🙋🏻‍♂️

I’m going to show you how to leave all those USB devices behind and remotely connect to them over the network instead. Yup, you heard right–you’ll finally be able to work from a laptop tied to a tree! (or at least from the comfort of your own couch…)

VirtualHere Link to heading

A while back, I was looking for a way to fire up the debugger on a STM32 NUCLEO development board without having the board directly connected to one of my laptop’s USB ports.

DIY home office electronics workspace

Tue, 28 Jun 2022 00:00:00 +0000

The idea Link to heading

I’ve been wanting to set up a small electronics workspace in my home office for a while now. The main goal was to have an ESD-safe area in the office where I could do bring-up and testing for projects that require a connection to a computer and test equipment. I already have a separate full size electronics workbench in the garage (SMT reflow oven, hot air rework, microscope, etc), so this was intended as a more focused compliment to that space, rather than a replacement for it.

Using giscus for comments in Hugo

Sun, 26 Jun 2022 00:00:00 +0000

After looking into a couple different hosted options for enabling comments on this site, I decided to give giscus a try.

This article describes why I chose giscus and how to set it up in a Hugo site.

First: why giscus? Link to heading

It’s worth talking through the thought process for how I landed on giscus, as it’s probably not the right option for everybody.

Derek Kay has an excellent article which explores various ways to include comments on a static site. After reviewing many of the options he mentioned in the article, I found that I mostly agree with his conclusion:

Bash shell startup files

Fri, 24 Oct 2014 00:00:00 +0000

This article is an attempt to answer the following questions¹:

What is the difference between /etc/profile, ~/.profile, ~/.bash_profile, ~/.bash_login, and ~/.bashrc?
Why doesn’t Terminal.app read my ~/.bashrc on Mac OS X?

Bash startup Link to heading

When Bash is invoked, it reads and executes commands from its startup files to set up the shell environment.

There are a couple conditions Bash checks to determine which startup files are read (and which ones are not) when the shell is invoked:

Understanding the INA219 I2C Current/Power Monitor

Sun, 06 Jul 2014 00:00:00 +0000

Motivation Link to heading

The INA219 datasheet provides an example calibration workflow, but doesn’t really explain how some of the equations and constant values are derived. This article tries to fill in some of the gaps that weren’t obvious to me when I first read the datasheet.

Overview Link to heading

“The INA219 is a high-side current shunt and power monitor with an I2C interface. The INA219 monitors both shunt drop and supply voltage, with programmable conversion times and filtering. A programmable calibration value, combined with an internal multiplier, enables direct readouts in amperes. An additional multiplying register calculates power in watts. The I2C interface features 16 programmable addresses.”

Current Projects

Mon, 01 Jan 0001 00:00:00 +0000

Common Ground Electronics :: A boutique embedded systems engineering services firm

Past Projects Link to heading

Flying Camp Design :: Open-source hardware development tools for the early Internet of Things

Moteware :: Open-source electronics disseminator for research groups and education

Get in touch

Mon, 01 Jan 0001 00:00:00 +0000

I love hearing from new people — please feel free to email me!

I’m always up for chatting about electronics, collaborating on product ideas, or anything else you’ve got in mind.

Hi 👋, I'm Chris

Mon, 01 Jan 0001 00:00:00 +0000

I’m passionate about technology that makes electronics more open, approachable, and accessible to everyone.

I spent most of my career working as a hardware design engineer specializing in embedded systems designed for the Internet of Things. More recently, I took a hiatus from design work and pivoted into a product management role at a PCB assembly manufacturing startup.

Currently, I’m bootstrapping Common Ground Electronics, a boutique embedded systems engineering services firm.