v1
==

fixes v0 short comings:

- shield LED is on when both shell are interconnected and connected to ground (the cable could cheat by just connecting both shells directly to ground)
- all GND and VBUS pins of USB-C are used

v0
==

first prototype build.

it works, but almost only on specification compliant cables:

- some cables don't have all 4 GND and VBUS pins in the C plug
- normally the shield should connect both shells AND be tied to ground on BOTH ends, but I've seen ALL possible combinations thereof