What I learned selling 2,500 MIDI recorders: Hardware is not so hard

I dislike this statement. Hardware is as hard as the product dictates it needs to be. A 25 component PCBA and a clamshell of 2 injection molded parts is about as simple of a product as you can make. Heck, most people would just buy an off the shelf clamshell for that type of product.

That doesn't work for the vast majority of products, building a product with 20 COTS parts plus 60 custom tooled parts, and 4 complex PCBAs is what is hard. Getting everything to fit together, pass testing, arrive on time from dozens of suppliers, etc. it where the complexity comes in. Then consider that hardware is cash intensive, you need to pay ahead of time for all the tools, you need to pay to buy the individual parts and warehouse them somewhere while you build the products you hope are going to sell. If something goes wrong there, then your expensive parts are just sitting there waiting for replacement components before you can ship. Then even when you ship, that revenue goes into buying the next round of parts you are going to receive in 3 months. This is where many hardware projects fail as they run out of cash before the project breaks even.

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.

The value you have created is actually more in the App than in the hardware.

As a maker of small devices (mostly open source) including MIDI - and putting aside commercial aspects like injection molding - I could recreate the hardware side of this project without much issue. The necessary components are likely already in this room with me. (I won't - I'm not in the business of copying things that people don't want copied)

But I'm not a software engineer, and therefore could not produce software of the scope and quality that you have, which is where the unique functionality of your device sits high above the relatively simple "receive MIDI data from MIDI devices" principle of the hardware by itself.

I don't disagree. It's important for us to recognize that we stand on the shoulders of giants, but I also think it's a little silly of a critique of someone happy about it being easier than he expected. It's true that hardware would be much harder if you had to do it all yourself, but is that meaningful? The wonders if the modern supply chain is that you don't need to do it all yourself.

And, well -- that's certainly good.

But the FCC rules cover more than just Wifi and BT, and the whole rest of the widget also needs to comply with them. Of particular interest is FCC Part 15 Subpart B, which covers unintentional radiators. The device would need to comply with Part 15 Subpart B even if it had nothing to do with Wifi or BT.

Putting one part that is certified for one issue into a device doesn't extend a magical blanket of compliance to everything else that the whole of the widget contains.

Does the SPI or I2C bus (or anything else) leak RF beyond allowable limits? Eh, who knows. I certainly don't know. It's easy to say words like "it should be fine," but without testing then nobody actually knows.

The CE mark, meanwhile: That mark means exactly nothing in the US, where the author is located and the devices are sold from. The United States has zero regulatory recognition of any of the processes and/or tests that CE may cover. People often confuse this issue, wherein: They don't think it be like it is, but it do.