Eleven days ago, I was accepted into the Founders Inc. Blueprint hardware accelerator. This program invites 20-40 builders (and teams of builders!) to join @fdotinc at their lab in San Francisco's Marina district to accelerate and event launch hardware products.
"Our programs are designed to get you from -1 to 0. They usually are 4 to 6 weeks where you lock in and create as much momentum alongside a cohort of other builders in the same spot. We provide office hours and other help and hold you accountable each week." https://f.inc/about
So of course, the very next morning after being accepted, ten days ago on September 26th, I packed my entire home office and homelab tools and gadgets into a car and drove west. Three days later at 10pm on September 30th, I arrived in San Francisco ahead of orientation at 11am on October 1st.
I'll be working here in SF on my standalone podcast/YouTube/whatever mixtape. I'm keeping the product name a secret—just call it Patrick's Mixtape for now—and it's a retro-inspired hardware mixtape that your favorite creators on YouTube and Apple Podcasts and Spotify can use to self-publish their own audio tracklists and mixes of YouTube and podcast content. Incoming orders would be flashed and fulfilled from my very own apartment-turned-warehouse-maybe in Chinatown NYC. And the e-ink display(s) will arrive pre-programmed with the creator's album art and track listing visible through the clear jewel case enclosing the mixtape—even while powered off.
The Blueprint accelerator lasts 5 weeks until November 7th. I sat down and recorded a short video covering my progress the first week. A transcript and some developer notes on the CAD software library I used, build123d follow the break.
Developer Notes
For the builders out there, the tools used in this video were Cursor IDE copilot, the Python software library build123d, and Blender. The CAD renderer you see used in the browser hosted on localhost is bernhard-42/vscode-ocp-cad-viewer.
Using a CAD-as-code library like build123d or cadquery is hella' useful for integrating with LLMs and AI copilots since they understand text the best.
I used this LLM copilot-written script hot.py to monitor my CAD files for changes to automagically hot reload updates in the browser CAD GUI.
Finally, it can be useful to provide Python library docs to copilots like Cursor IDE from directly on your filesystem. There are lots of tools and tooling for empowering your copilot to download docs from the web, but I kept it simple and simply downloaded the .epub version of the docs from the build123d documentation website (you can access epub from bottom-right menu).
# 1. download the .epub documentation for build123d
cd /tmp
wget -O build123d.epub 'https://build123d.readthedocs.io/_/downloads/en/latest/epub/'
epub2txt ./build123d.epub | tee build123d.txt
wc -l build123d.txt
# output: 13095 build123d.txt
# 2. convert to text using epub2txt2
cd /tmp
git clone git@github.com:kevinboone/epub2txt2.git
cd ./epub2txt2
make
sudo make install
which epub2txt
# output: /usr/bin/epub2txt
In order for you your Cursor copilot to know to reference the build123d during its work, you can create a .cursor/rules/parts-cad.mdc file that looks similar to this:
---
description: CAD files written in Python using cadquery and build123d libraries
globs: cad/**/*
alwaysApply: false
---
<start of parts-cad.mdc rules file>
You are a gifted mechanical and electrical engineer. You are assisting in producing CAD parts and assemblies that can be used for product rendering and mass production.
Each file in the `./cad` represents a CAD part or assembly.
We are using the Python `build123d` library to design CAD parts, you must always read ./docs/build123d.txt which is the latest documentation for this library.
## Testing changes
Generally, the entry-point to test changes to make sure everything compiles correctly should be the relevant CAD assembly e.g. `python ./cad/v1/assembly.py` rather than an individual part file.
## Style rules
* Do *not* use the `MM` unit or any other unit descriptor in Python code (cadquery and build123d). All values should be raw floating-point numbers without any unit symbol (or multiplied to any unit symbol).
## Updates to `.cursor/rules/*.mdc` files.
You must always re-read loaded rules files for new instructions before outputting a new deliverable `output.md` file.
</end of parts-cad.mdc rules file>
Video Transcript
TRANSCRIPT
Hello, this is Patrick.
Welcome to day seven of Blueprint here at Fort Mason campus in San Francisco.
One of the things I'd like to do during this program is to kind of check in every morning and discuss what I got done yesterday and what I'm planning to do today.
So yesterday I was working mostly on the mechanical assembly for the prototype. Now really my only design constraint is that I want this to be the exact same dimensions to fit in a conventional traditional jewel case for a cassette tape, only this is its own kind of slab design.
One of the niceties I accomplished yesterday is adding what I'm calling the chisel here, which is supposed to kind of mirror the same type of chisel that's on a jewel case for a cassette. The technology I kind of use to work on it is quite interesting. I'm able to use LLMs like ChatGPT or Claude or whatever, and so even here I have this whole setup with hot reloading.
So if I go here and be like please change the angle of the trapezoid cutout for the E-ink display to 38°, the LLM will go through and take care of the CAD design for me, which is quite great because of course I'm a firmware engineer and not a mechanical engineer, and if we go here we see indeed that it has gone and changed the trapezoid here.
So I accomplished adding the cutout for the USB-C port, I still need to add cutouts for the power button, the volume buttons, the next track, previous track, etc., but these should be ready to export and begin printing on some of the Bambu 3D printers here.
So that's a lot of like slacker time where I'm just going to be waiting like two hours for the housing to print, so today my intention is to actually figure out, work more on the electrical bill materials, like everything that actually goes into the first production run bill materials, but then also unfortunately I don't know if I'm good enough to actually prototype a first spin of the PCB that will fit in here and be the size of like a business card or a credit card, so I may make a 4-to-1 scale model that's somewhat bigger that at least I can like breadboard at ESP32 and the rest, and so that will come, I'll make that decision today.
One other piece though I do want to share is again, I am also, what's great with all these CAD models, I'm able to export to Blender, and so you see here the idea is that when you make a mixtape as a gift for someone, and obviously subject to whatever type of licensing deals I can make with creators, if track 1 is a YouTuber, then it gets like a red housing, green for music, this very familiar purple color would be for podcasts, and this very familiar yellow orange color would be for audiobooks.
I'm playing around with the idea, I don't think I'm going to let people customize any more than that, like if you want a red mixtape then you have to put track 1 as like a YouTube narrative video, and I think it is cool to have like full color on the front, but I think people would get sick of that, so I think it's going to be black and then kind of the accent color will be at the bottom here.
And for the prototype I'm going to have to have these screw bosses on the back that screw into the back of the display, so I've actually, and I'll turn around for the video here, camera, I did do a test print yesterday.
I'm able to put like a little brass insert in here, so rather than like deforming the plastic every time I try and screw a thread in a screw, there's these brass inserts that are already pre-threaded, so that's what I'll be using for the prototype, but the production design for manufacture will probably be either like snaps or glue or something like that. And that'll be someone else's problem, because I am not a DFM mechanical engineer.
So again, today, try and get a couple of these test prints made for this housing here, which, you know, if I make transparent, you can see, you know, this is the top side with the screw bosses, and then the bottom side with the through holes for the screws, and that's the plan for today. These test prints, and then also work on ordering some electrical off-the-shelf parts for the prototype, and then also, you know, doing the unit budget for the production model.
So, that's my update. Thank you.
