Building One Thing In China

Conventional wisdom dictates that if you need to make a million of something, you go to China. China is all about manufacturing, and there aren’t many other places on the planet that have the industry and government-subsidized shipping that will bring your product from China to people around the world. Building a million things in China is one thing, but what about building one thing? How do you create a working prototype of your latest product, and how do you make that prototype look like something that isn’t held together with zip ties and hot glue? The folks at Hatch Manufacturing have a guide for doing just that, and lucky for us, it’s a process that’s easy to replicate in any well-equipped shop.

In this tutorial/case study/PR blitz, Hatch Manufacturing takes on constructing a one-off smartphone. The Huaqiangbei markets in Shenzhen are filled with vendors selling smartphones of all shapes and sizes. If you want a miniature iPhone running Android, that’s no problem. If you want a phone that looks like a 1969 Dodge Charger with the Stars and Bars on top, you can find it in China. But how are all these phones made, and how do you show off a prototype to factories begging for business?

The answer, as is always the case, comes from one-off manufacturing. Building, assembling and reworking PCBs is a well-trodden path whose process could fill several volumes, but for this post, Hatch Manufacturing decided to focus on the plastics that go into a smartphone or tablet.

Once the case or enclosure is designed with a few CAD tools, a block of plastic is run through a mill. After that, it’s a matter of painting and finishing the latest smartphone that will show up in the Chinese market. Putting a professional finish on a block of plastic is something that will look familiar to anyone who has ever assembled a miniature plastic model. There’s priming, airbrushing, sanding, more painting, sanding, wet sanding, and still more sanding. After that comes polishing the plastic part to a fine finish. It is extraordinarily labor intensive work even for a skilled hand with the right equipment.

Once the plastics are done, the PCB, display, battery, and everything else comes together in a completely custom one-off prototype. It’s very similar to how this would be done in any small shop with a benchtop mill and a dozen grades of wet/dry sandpaper. It’s also something anyone can do, provided they have enough practice and patience.

Snooping On SIM Cards

[Nils Pipenbrinck] has been working on a very interesting problem. The SIM card in your cellphone talks to the contactless near-field communication (NFC) chip through a cool protocol that we’d never hear of until reading his blog: single wire protocol (SWP).

The SIM card in your cellphone has only a limited number of physical connections — and by the time NFC technology came on the scene all but one of them was in use. But the NFC controller and the SIM need full-duplex communications. So the SWP works bi-directionally on just one wire; one device modulates the voltage on the line, while the other modulates the current, essentially by switching a load in and out.

This signalling protocol makes snooping on this data line tricky. So to start off his explorations with SWP, [Nils] built his own transceiver. That lead [Nils] to some very sensitive analog sniffer circuit design that he’s just come up with.

If you get interested in SWP, you’ll find the slides from this fantastic presentation (PDF) helpful, and they propose a solution very similar to the one that [Nils] ended up implementing. That’s not taking anything away from [Nils]’s amazing work: with tricky high-speed analog circuitry like this, the implementation can be more than half of the battle! And we’ll surely be following [Nils]’s blog to see where he takes this.

Banner image: An old version and a new version of the transceiver prototype.

Thanks to [Tim Riemann] for the tip!