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Comment by duttish | Hacker News Reader

Wait what. I thought half the point of usb c was to not rely on orientation.

Is there any way to check this other than experiment?

My "solution" so far has been to not buy cheap cables and just hope I get quality in return.

> I thought half the point of usb c was to not rely on orientation. > Is there any way to check this other than experiment?

Well sure, a standards-compliant cable will work in either orientation, but it's always possible for some but not all of the pins or wires to break.

I believe USB C cables actually do have an orientation - it's just that the negotiation both ends do usually makes that orientation irrelevant.

Maybe the negotiation can fail & the plugged in orientation is then the only one that works?

USB-C only has an "intrinsic" orientation because we call one set of pins "1" and the other "2". Electrically there should be no difference.

No, there really is an intrinsic orientation, at least once a cable is plugged in.

The receptacles are symmetric, but a full connection is not. The cable only connects CC through end-to-end on one of A5 or B5, but not both, which lets the DFP detect which of A5 or B5 should be CC. The one not used for CC is then used to power the e-marker in the cable, if any.

This is also true for legacy adapters; for example, for C-to-A USB 3 adapters, the host needs to know which of the two high-speed pairs to use (as USB 3 over A/B connectors only supports one lane, while C supports two).

I think that I have a specific cable-device-orientation that is broken. Meaning, I think a particular USB C cable won't charge my phone if it's plugged in 'backwards'.

I always assumed that USB C cables use different pins depending on orientation, and that some pins on the cable wore down.

Maybe that's what happened here?

I think a more distressing thought is that it’s quite possible that your cable won’t charge your phone if it’s plugged in forwards.

My guess would be they used a one-sided pcb to connect the cable to and used half the wires. Some sockets internally link the power and ground pins, so it works both ways, but you get no resistor network and thus only standard 5v which gives you 500ma max (at best). With the resistors connected by the cable it's about 900ma to 3a which is probably what happens plugged in "correctly". Or some other magic happens on one side of the PCB to fool the charger into pushing the full 3A.

Shouldn't a compliant USB-C DFP not supply Vbus without the resistor network, though, so there should be no charging at all? (Not that all DFPs necessarily do the correct thing, of course.)

Correct, which is probably why it won't even charge their earbuds in the broken orientation.

It's CC2/VCONN used for eMarker. That pin may be terminated inside the cable and used to power eMarker chip. It can also be used for orientation sensing. I think.

It happens. More often than not, it can be physical damage or manufacturing defect for one of the contacts and/or wires.

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