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Comment by seba_dos1 | Hacker News Reader

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seba_dos1

> Pick a USB cable and buy it from ANY retailer, let's make it easier, buy a USB-C cable.

Okay, let's assume it's a USB-C cable and not just something USB-C shaped that pretends to be one.

> Does it support power delivery?

Yes.

> If so, how many watts?

Always at least 60W (3A). Up to 240W if it's e-marked.

> What is the data rate

Depends whether it's a USB 2.0-only cable (480Mbps) or a complete cable (20Gbps). Possibly more in Thunderbolt or USB4 modes - cables that handle those will be marked (both visually and with an e-mark). In any case, pretty easy to check just by plugging things in.

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But how do I know if a random cable that comes with a device I bought is just something USB-C shaped or the real thing? How do I know the same thing on Amazon or whatever other big retailer with thousands of cables I use?

The last time I bought one I looked for one with a proper certificate but that eliminated the vast majority of cables on Amazon and I suspect that I ended up buying something ridiculously over engineered.

No one explains it this way for some reason, but USB-C "60W" is more like USB-C 20V. All USB C-to-C cables are supposed to be rated to something like 600V by laws and common sense, and 3A by USB-C spec. 20V x 3A = 60W.

USB-C in C-to-C configurations require all the PD pins working for voltages to be supplied at all. So all USB-C cables that aren't the ones that actually don't work at all should be able to do that 20V x 3A -> 60W. Only in rare cases where a C-C cable is wired to make it look like one by being internally wired as C-A-A-C it becomes problematic since only USB-C has the config pins used for non-5V modes, but that should be actually rare.

I think USB-C shaped thing mentioned in GP refers to USB-C devices, like dollar store Bluetooth speakers and such. For those things, it's in fact not so rare that they come with tons of stupid quirks.

The can of worms is mainly in USB 3.0, Alt Mode, 5A mode, and Thunderbolt/USB4. 3A mode is fine. Raspberry Pi notoriously used a "5V 5A" mode that it's not supposed to be using.

> Only in rare cases where a C-C cable is wired to make it look like one by being internally wired as C-A-A-C

Such cable would have to be directional, so you'd quickly realize something's wrong with it. I rather meant things like "power-only" cable, which can't exist and be complaint simultaneously. I've also seen non-compliant USB-A to C cables having incorrect/missing resistors and causing troubles.

In any case, the point was that this is just counterfeit shit to be thrown away. Take literally any other connection standard and I can also make a cable that looks like it's real but doesn't actually work, it's trivial.

You're right that it's much easier to find a USB-C-shaped shitty device than a USB-C-shaped shitty cable - and it's astonishing how little would usually be needed to make it complaint and working correctly. Since using some kinds of cables can mask some of the device's issues, people end up incorrectly blaming the cables.

I don't know why you got downvoted so much. There's no such thing as a 5 watt USB cable from a reputable source and people need to stop acting like there is. 60 is a very good baseline. There's no such thing as a power only USB cable either.

If we're counting fake products then we need to count those RGB sticks that have no RAM in them.

You couldn't even make a 5W USB-C cable if you tried. You'd have to make the wires so thin that it would burn at above 1A I guess, and it would have no way to signal the device to limit its power consumption to 1A, so it would just burn once you tried to use it. All you need to handle 60W is to make three electrical connections between the ends, and the cable won't work at all if you miss any.

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