Re:The impossible dream of USB-C
by cesarb on Sunday October 15, 2017 @09:13AM
(#15476966)
> From my (possibly flawed) understanding, because USB-C switches modes to carry something like DisplayPort, for example, you can't also carry a USB-C signal at the same time
A USB-C connector has one USB 2.0 pair, four high-speed differential pairs, and two sideband wires. For USB 2.0 you need only the USB 2.0 pair, for USB 3.1 you need the USB 2.0 pair and two of the high-speed differential pairs.
For DisplayPort, you need two or four of the differential pairs, plus the two sideband wires. If you're using two of the differential pairs for DisplayPort, you can use the full USB 3.1 at the same time; if you're using four of the differential pairs for DisplayPort, you still have USB 2.0 left.
The same applies to other alternate modes. As long as they need at most two of the differential pairs, you have USB 3.1, otherwise you have USB 2.0. And power delivery has its own set of wires, so it's also always available.
(The exception is the 3.5mm plug adapter alternate mode, where everything except analog audio and slow charging is unavailable.)
A USB-C connector has one USB 2.0 pair, four high-speed differential pairs, and two sideband wires. For USB 2.0 you need only the USB 2.0 pair, for USB 3.1 you need the USB 2.0 pair and two of the high-speed differential pairs.
For DisplayPort, you need two or four of the differential pairs, plus the two sideband wires. If you're using two of the differential pairs for DisplayPort, you can use the full USB 3.1 at the same time; if you're using four of the differential pairs for DisplayPort, you still have USB 2.0 left.
The same applies to other alternate modes. As long as they need at most two of the differential pairs, you have USB 3.1, otherwise you have USB 2.0. And power delivery has its own set of wires, so it's also always available.
(The exception is the 3.5mm plug adapter alternate mode, where everything except analog audio and slow charging is unavailable.)