connector design

2 Articles

On the left, four through-hole USB-C connectors laid out on a purple cutting mat. On the right, a teardown picture shows that there's neither resistors nor CC connections inside such a connector, resulting in consequences described in the article.

The USB-C Connectors You Never Knew You Wanted To Avoid

February 20, 2022 by 24 Comments

On Tech Twitter, some people are known for Their Thing – for example, [A13 (@sad_electronics)], (when they’re not busy designing electronics), searches the net to find outstanding parts to marvel at. A good portion of the parts that they find are outstanding for all the wrong reasons. Today, that’s a through-hole two-pin USB Type-C socket. Observing the cheap tech we get from China (or the UK!), you might conclude that two 5.1K pulldown resistors are very hard to add to a product – this socket makes it literally impossible.

We’ve seen two-pin THT MicroUSB sockets before, sometimes used for hobbyist kits. This one, however, goes against the main requirement of Type-C connectors – sink (Type-C-powered) devices having pulldowns on CC pins, and source devices (PSUs and host ports) having pull up resistors to VBUS. As disassembly shows, this connector has neither of these nor the capability for you to add anything, as the CC pins are physically not present. If you use this port to make a USB-C-powered device, a Type-C-compliant PSU will not give it power. If you try to make a Type-C PSU with it, a compliant device shall (rightfully!) refuse to charge from it. The only thing this port is good for is when a device using it is bundled with a USB-A to USB-C cable – actively setting back whatever progress Type-C connectors managed to make.

As much as USB Type-C basics are straightforward, manufacturers get it wrong on the regular – back in 2016, a wrong cable could kill your $1.5k MacBook. Nowadays, we might only need to mod a device with a pair of 5.1K resistors every now and then. We can only hope that the new EU laws will force devices to get it right and stop ruining the convenience for everyone, so we can finally enjoy what was promised to us. Hackers have been making more and more devices with USB-C ports, and even retrofitting iPhones here and there. If you wanted to get into mischief territory and abuse the extended capabilities of new tech, you could even make a device that enumerates in different ways if you flip the cable, or make a “BGA on an FPC” dongle that is fully hidden inside a Type-C cable end!

What’s In A USB-C Connector?

October 27, 2020 by 30 Comments

Anyone who’s ever put together a bill-of-materials for an electronic device will be familiar with the process of scouring supplier catalogs and data sheets for the best choice of components. The trick is to score the best combination of price and performance for the final product, and for those unused to the process, there are always seemingly identical products with an astonishingly wide variety of prices. It’s a topic [Timon] explores in a Twitter thread, examining a 20-cent in quantity of 100 USB-C socket alongside one that costs only 5 cents, and his teardown provides a fascinating insight into their manufacture.

The parts look so nearly identical that while it’s possible to differentiate between them visually, it’s near impossible to work out which was the cheaper. Some tiny features such as a crack in a metal fold or a bit less plating on the contacts emerge, but even then it’s no guide to the quality as they don’t appear on the same part. It’s only when the metal shell is removed to expose the underlying plastic moulding that more clues emerge, as one moulding is more complex than the other. The more complex moulding provides a better and more reliable fit at the expense of a much more costly moulding process, so at last we can not only identify the more expensive part but also see where the extra cash has gone. It’s a subtle thing, but one that could make a huge difference to the performance of the final assembly and which makes for a fascinating expose for electronic design engineers.

If connectors are your thing, there’s a wealth of fascinating information in their history.