> This one "sniffs" the link just for the Power Delivery negotiations that happen at the lowest electrical levels. If a device or cable is misbehaving, a knowledgeable person should be able to replicate the problem and see it happening with the sniffer. They could see which component was not following spec, and most importantly, exactly what it was doing wrong. > > Even if your computer is participating in Power Delivery, it can't see its own PD traffic because all that is handled at a low level by ASIC chips in your USB port. Hence the need for a separate physical device to see the signals that are actually being sent on the wire.

https://www.reddit.com/r/UsbCHardware/comments/qmz9uz/twonki...