5 ms·
> Then you implement auto crossover detection, dwhich had been around for years Mdi-x/auto crossover for ethernet was introduced in 1999, that is after USB (19
by gzalo 3y ago
> Then you implement auto crossover detection, dwhich had been around for years
Mdi-x/auto crossover for ethernet was introduced in 1999, that is after USB (1996) was designed, not sure of the technique was known at that time
- dboreham 3y agoThere were auto-crossover RS-232 boxes going back deep into the 1980s.
- sitzkrieg 3y agowith baud rate detection to boot (down the line)
- deleted 3y ago[deleted]
- userbinator 3y agoYou can't do "auto crossover" with USB because it needs to distinguish between D+/D- for speed selection. https://electronics.stackexchange.com/questions/73295/in-a-usb-cable-is-it-ok-to-swap-the-d-and-d-wires https://electronics.stackexchange.com/questions/73295/in-a-u... It works for Ethernet because the transmit and receive lanes are separate, but with USB, there's only one pair used for both directions.
- ilyt 3y agoIt doesn't need to. It chose to. They could just use different way to do it. Like, I dunno, a single packet of negotiation in slow mode...
- crote 3y agoNot really relevant. Ethernet needs crossover because it has dedicated transmit/receive pairs, but USB 1.x/2.0 uses a single wire pair for both tx & rx. Ethernet crossover is pretty much identical to serial null modem cables, and those were around for a few decades by then. USB "crossover" of the single differential wire pair would be an inversion of 0 and 1. Pretty trivial to do once you figure out a way to communicate crossover or not.