chipweinberger

The app is not required if you access the midi files from the sd card. You don't even need to install it.

The app is optional, and its for browsing your library. Think of it like the Photos app but for MIDI.

Counterfeit != clone. I welcome competitors. They can help grow the pie.

If you consume power over USB-C, 2 resistor are enough.

But for providing power over USB-C, you generally need a dedicated IC to handle VBUS switching. It wasn't worth it.

Also, once you ship a consumer product with a USB port on it, you'll realize a lot of people really don't understand how USB works, and USB-C doubly so. Square holes for square pegs goes a long way.

I appreciate the critiques!

First, so far, there have been 0 failures in the field. My email address is on the website, the app, and the first page of the instruction sheet, so I'd probably know if there were.

But since it's fun, I'll address some of these :) I'm not flying by the seat of my pants here as much as you expect.

- The ESP32-S3 includes ±2 kV ESD, which is respectable. Adding more is a bit precautionary IMO, but I did add it in some places where the user is more likely to touch metal (like the USB ports). The sdcard's metal housing is not exposed.

- The AMS1117 is just more available than the alternatives. Again, no failures yet so seems like the right tradeoff was made here.

- Supercaps don't last long enough for my liking. A CR2032 can go for 10+ years. A supercap, only weeks. I want correct dates even if the device is left unpowered for months.

- The 0603 47ohm resistor is a good callout. Worth beefing that up. But at 3.3v and 232 mW it's not a fire hazard. It will fail open.

- USB-B for power was very intentional. It's a great firm connector and more importantly prevents users from plugging it into their piano wrong. Many of my customers are in their 70s or older.

- USB-A for data was made for simplicity, but again, USB-C is too complicated for many of my users. I'd only switch to USB-C if both ports could be used interchangeably, but they can't be / it's not worth the complexity.

- As for the software moat, time will tell. You can't stave off competition forever!

- The device is FCC and CE compliant.

Again, I actually do appreciate your critiques!

500 units was my first run, and it worked out really well. None of the suppliers complained about that order size. I recommend starting with a smaller quantity until you've validated the market. The "economies of scale" between 100, 500, or 1000, units are not all that dramatic. Perhaps 30% cost difference.

I was originally planning to do 4000 units as my first run. Boy I'm glad I started to run out of money and cut it way back. That would have been way too much as a first run.

The device does not require the app. It still records MIDI 24/7 to sdcard.

It's more the opposite. The app requires a genuine device.

Will do a write up on injection molding and anti-counterfeit!

Not technically custom, but made to order (I gave them a spec sheet). If they had reasonably priced connectors on LCSC or DigiKey, etc, I would have used them!

The marketing answer: all lower-case looks modern and opinionated

The real answer: I got tired of deciding what should and shouldn't be capitalized. Sounds easy but it gets ambiguous fast.

I'll revisit this decision at some point. Capital letters do make reading easier.

I don't entirely disagree. Just one sample point. But there are certainly much more simplistic hardware products out there. I'm often envious of them.

Here's a good example: https://duckduckgo.com/?q=brick+smartphone+blocker&ia=web

Yes the anti-counterfeit is primarily app enforced (though entirely offline). I do use the firmware encryption features of the ESP32-S3, whatever that is worth, and the firmware is tied to the HSM.

Ahah good eye. It was only 4 blocks down the road! I too was surprised by how well a single cord worked to balance the 45lb boxes.

Android too! Built with Flutter. Flutter is great highly recommend it.

This is very flattering. Thank you.

3 main components: flashing, provisioning keys, hardware testing.

Nearly every component gets tested: sdcard, clock, battery, anti-counterfeit IC, led, buzzer, the tactile-switch!

Yes I've seen a few people mention that! All of the best MIDI hardware recorders are ancient, for whatever reason. Well, apart from Jamcorder ;)

It sort of is. I'm at an annoying scale where most 3PLs don't want to deal with me yet.

At the same time, it doesn't take much time at all, and is a good excuse to get out of the house!

I started with having watched ~100 hours of EEVBlog :)

Electronics, PCBs, CAD, injection molding was all new to me.

They should just work! You can replace the soundfont that the app uses with your own too.

IMO it's better to ship preprogrammed ICs to the factory, so you can do your secure burning in-house.

These numbers do not include ESP-IDF :)

I chose to do FCC only and CE self-certify. If you use pre-certified radios it's not as expensive as you think. $5K should be plenty if you ask around. Just make sure you design your board so you actually pass, and don't let the labs over-sell you. They'll try to!

99.99% of cheap Chinese products you buy on Amazon don't actually have this testing done at all. So by doing any testing you're already way above them.

I'm using an STSAFE chip - the same IC they use in StarLink terminals. Essentially the digital equivalent of a holographic barcode. I have some other protections too. e.g. Random 128-bit per-device IDs / product-keys. iMessage uses this strategy.

Maybe I'll write an article about that.

The app is about 85K lines: device connectivity, first-time setup, syncing, MIDI playback and visualization, library management, audio/video export, and OTA workflows.

The firmware is about 110K lines: MIDI recording + streaming, USB, Bluetooth, Wi-Fi, web APIs, storage, OTA updates, diagnostics, security, peripherals, provisioning, and an embedded web interface.

There’s a lot required to make a full-featured product.

Spending too long on the firmware. I almost ran out of runway. I should have cut features faster. And I should have built the firmware cross platform so I could run it my local machine. Every compile + flash loop took 2+ minutes.

I'll be sticking around in the comments so feel free to ask questions. AMA!

The D-Link DSR-150 was released in 2012

It was the first information I wanted to know, but it wasn't in the article.

Yes you can do that.

Buy a standard midi to usb adapter (~$20), then do:

piano -> (usb) -> Jamcorder -> (midi out) -> adapter -> (usb) -> pc

It should give acceptable latency for real-time recording.

made improvements. It's now about 12ms constant. Usable for real-time playback.