3 ms·
Just imagine this: Device A <--> Device B Device A receives the cable first, upon receiving the cable, Device A notices that the cable is not "hot" ("hot" in t
by cbluth 9y ago
Just imagine this: Device A <--> Device B
Device A receives the cable first, upon receiving the cable, Device A notices that the cable is not "hot" ("hot" in the sense that there is voltage/activity on the wire), so then Device A decides to "turn on" the cable, make it "hot".
Now Device B receives the cable, it notices that the cable is already "hot" and decides that it must be the second device.
I would imagine it could work that way,
Im also pretty sure that the usb cables are "dumb" cables and not active cables like QSFP (these have chips at each end).
- lopmotr 9y agoThat assumes a device can tell the difference between not hot and not there, which was the parent's question.
- arghwhat 9y agoThis is not how USB Type C works. The cables are active (chipped), and the end devices have sense resistors. Each device can detect the presence and type of the cable, as well as the presence and type of an end device and total cable orientation (swapped or not). This is all done before power is applied, as USB Type C is very explicit about not going hot (apart from a weak 5V V_conn for powering the cable). Also, QSFP is not a cable, but a pluggable spec. A QSFP module is active, but the fiber optic cable you connect to it to is dumb. Link detection there works by sensing beam power.