Cursed USB-C: When Plug Orientation Matters – Hackaday2 min read

https://hackaday.com/2021/03/22/cursed-usb-c-when-plug-orientation-matters/

Among the selling points of the USB-C plug is that supposedly there is no other way to incorrectly insert it. As [Pim de Groot] shows with a Cursed USB-C 2.0 Device, reality is a bit more made complex when it concerns USB 2.0 compatibility in USB-C. He made a PCB that elegantly shows the simpleness of the problem, featuring two LEDs. Just one orientation of the USB-C plug will cause one of the LEDs to illuminate green, with the other orientation leaving both LEDs blinking red.
Sigil on the back of the cursed USB-C 2.0 gadget, by Pim de Groot.
Normally you would connect the matching lines in these pairs together to ensure constant behavior no matter the plug orientation, but you do not have to.
By leading each USB 2.0 information set to its own SAMD11C MCU, just one of the MCUs would be linked to USB, leading to the connected MCU blinking the LEDs. With a bit more circuitry its possible to detect which way around the plug is placed and use this details in a single MCU system, altering its habits. While in the beginning glimpse this seems bit more than a fun party trick, however it also provides insight in a possible failure mode of USB-C 2.0 gadgets where just one plug orientation works, due to damaged traces or pads.
Board view of [Pim]s Cursed USB-C 2.0 Device.( Heading image: Cursed USB-C 2.0 Device, by Pim de Groot).

Only one orientation of the USB-C plug will cause one of the LEDs to light up green, with the other orientation leaving both LEDs blinking red.
While at first glance this seems bit more than an enjoyable party technique, however it also offers insight in a possible failure mode of USB-C 2.0 gadgets where only one plug orientation works, due to damaged traces or pads.
( Heading image: Cursed USB-C 2.0 Device, by Pim de Groot).

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