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Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

arstechnica.co.uk

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Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#61

Post by Dylan16807 »

pluma wrote: post #25
sharpneli wrote: post #14

Earlier quoted context omitted.

It was not a slight fezz-up. It was miswiring in a power cable. It's like electrician wiring the live pin into ground pin and then wondering why one gets electrocuted by so many devices. No specification can defend against a hostile, or sufficiently incompetent, implementer.

I have actually seen a wall plug with V- and GND mixed up. Luckily nobody was injured and nothing was set on fire, but we did wonder why touching the dishwasher gave us a noticeable shock until we figured out what was wrong.

Assuming you mean neutral and ground, at least those are nominally the same voltage. If you mean something else then I'm going to need more explanation of what wires are in that plug, and I'm slightly terrified that it still ran.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#62

Post by sharpneli »

Dylan16807 wrote: post #60
Bjartr wrote: post #54

Earlier quoted context omitted.

I t http://www.fiftythree.org/etherkiller/ttp://www.fiftythree.o... it's a matter of foreseeing the potential failure modes and correctly deciding which ones are so remote as to be not worth the cost and complexity to protect against. For instance, I don't think there's a consumer device out there that wouldn't fry if connected directly to mains AC through any peripheral port at all. But that doesn't stop someone fro…

A cable with a mains plug at one end and USB on the other is obviously wrong, though. Mains power is legitimately difficult to deal with. Power that's five volts out of spec is not.

A cable that puts 5 volts into random pin is also obviously wrong.

It's a balancing act between the probable failure modes and the cost of replacing the broken devices. Hostile manufacturers is not common enough of a failure mode (vs just Amazon sending a replacement device) to accept the additional cost for every single unit made. It makes no sense to spend 1 dollar more per device if it saves 1 cents per device on average for replacement costs.

If this kind of issue becomes more common then it might make sense. But for now it doesn't seem likely.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#63

Post by captainmuon »

Bjartr wrote: post #50
hagope wrote: post #22

I find my micro USB type-B connectors all eventually fail, and I've been combing through Amazon to find a reliable cable manufacturer, any suggestions?

This is actually by design, kind of. Mini USB didn't have this problem with cable connectors because the complexity was in the jack. Unfortunately that meant that when a failure did occur it was on the divide and couldn't easily be fixed. Micro USB improved on that by shifting the complexity to the plug side. So the cable failing eventually is down to a lesser of two evils engineering tradeoff.

Huh. I know it was the rationale behind micro USB that the jacks would be more reliable than before. But I've actually had multiple micro USB sockets fail, while I've never had a problem with a micro USB plug, or old mini USB plugs or sockets.

In particular, my Nexus 7 needed two replacement jacks. I gave up after the second replacement broke. Phone jacks also get a bit loose after a year or two.

Since micro USB (sockets) are supposed to be more stable, I'm wondering if I'm doing something wrong?

Also the stupid things collect lint in my pocket. I almost threw away a phone that couldn't be charged anymore, only to find I can revive it with a toothpick.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#64

Post by Arnt »

zyxley wrote: post #49
Arnt wrote: post #41

Earlier quoted context omitted.

Right... but two questions stick their head up and want answers: First, USB outlets are supposed to have a bit of a fuse. Why was this upfuckage so spectacular? Second, why do USB type C ports/cables have 24 pins if there are only 4 wires? I can understand having a couple of extra ones for type/orientation detection and a doubling to support reversion, but 24 is a lot.

> Why was this upfuckage so spectacular? Because it had power wired to ground. This would be incredibly absurd in ANY variety of powered cable. This is not merely "noncompliant with spec", it's "actively dangerous because it could start a fire and kill somebody".

I see. Of course it would be very difficult to defend against that. Thanks.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#65

Post by kimdouglasmason »

hagope wrote: post #43
coffeedrinker wrote: post #37

Earlier quoted context omitted.

Anker.

I like their charging products, but the cables have been failing at the connector...

Which kind of cable? If it's micro USB, they're designed to fail under low amounts of stress (thus sparing the much more difficult to replace port).

Unless handled with kid gloves, Micro USB cables from all manufacturer break easily.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#66

Post by tobz »

sharpneli wrote: post #20
josteink wrote: post #17

Earlier quoted context omitted.

Tomay-to/tomay-to. Yes, USB C can also be used to provide power (which is also a form of signal), but again my point is that a cable like this is largely expected to be a passive component. That a crap charger can do bad things would probably surprise no one, but hooking a good charger up to a good unit shouldn't be able to fry anything, ever. Wasn't USB C supposed to make our lives easier? If we need to ensure all o…

Hooking up a good charger up to a good unit with the ground and voltage wires reversed can fry things. You can try it with your laptop. Cut the cable after the transformer, flip the ground and live wires and start it. It will get fried. Is this the fault of the specification or the person who intentionally flipped the wires? The manufacturer was the person flipping the wires in this case.

In this case, it's DC over the USB-C cable. Reverse polarity protection is 1) easy and 2) cheap. That's the most striking part to me, and I almost thought the original post was a joke... because it seems insane there wouldn't be reverse polarity detection built-in to the laptop.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#67

Post by MatthewWilkes »

dawnbreez wrote: post #45

I'm not an electrical engineer, but wiring something other than ground to the ground pin is...well, I suspect it's straight-up malicious, although why you'd want to do something like this, I don't know.

So, there's a couple of interesting bits of context. Firstly, the way these dodgy cables try and suck more juice out of sockets is by putting passives between the data lines to trick the phone into a genuine OEM charger from the same manufacturer, so it ignores the USB power specs.

Secondly, the way USB declares that something is a host is by tying ground to the sheath.

So, there's precedent for tying things together (through a passive), and tying things to ground (but only things that are floating). MY guess is that they bought some connectors designed for USB host that had the sheath tied to ground and in their attempts to tie D+ and D- together shorted to ground. Only a guess though, you really don't want to do this.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#68

Post by Arnt »

mikeash wrote: post #53
Arnt wrote: post #41

Earlier quoted context omitted.

Right... but two questions stick their head up and want answers: First, USB outlets are supposed to have a bit of a fuse. Why was this upfuckage so spectacular? Second, why do USB type C ports/cables have 24 pins if there are only 4 wires? I can understand having a couple of extra ones for type/orientation detection and a doubling to support reversion, but 24 is a lot.

I don't know exactly why these ports aren't protected, but as for your second question, why assume there are only four wires, given there are a lot more pins? Wikipedia has a full pinout and wiring list and you can see there's a lot more going on than that: https://en.wikipedia.org/wiki/USB_Type-C#Connector_pinouts_a... USB-C is not merely a new connector for the old USB 2.0, but includes a lot more. It is backwards…

Why assume that, indeed. The salesman who sold me my lovely new macbook told me (when I said something skeptical about quick charging via a thin cable).

Feel free to vote me down for believing something a salesman said.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#69

Post by yincrash »

Arnt wrote: post #41
mikeash wrote: post #33

Earlier quoted context omitted.

What gives is that this was not actually a type C cable, but an evil, broken cable mislabeled as a USB-C cable.

Right... but two questions stick their head up and want answers: First, USB outlets are supposed to have a bit of a fuse. Why was this upfuckage so spectacular? Second, why do USB type C ports/cables have 24 pins if there are only 4 wires? I can understand having a couple of extra ones for type/orientation detection and a doubling to support reversion, but 24 is a lot.

I'm not sure any spec for a power cable protects against switching V+ with ground.

Re: Google engineer finds USB Type-C cable that’s so bad it fried his Chromebook

#70

Post by qb45 »

Dylan16807 wrote: post #60
Bjartr wrote: post #54

Earlier quoted context omitted.

I t http://www.fiftythree.org/etherkiller/ttp://www.fiftythree.o... it's a matter of foreseeing the potential failure modes and correctly deciding which ones are so remote as to be not worth the cost and complexity to protect against. For instance, I don't think there's a consumer device out there that wouldn't fry if connected directly to mains AC through any peripheral port at all. But that doesn't stop someone fro…

A cable with a mains plug at one end and USB on the other is obviously wrong, though. Mains power is legitimately difficult to deal with. Power that's five volts out of spec is not.

Just as a side note, some of the cheapest USB chargers have 1mm or so of clearance between high voltage and low voltage circuits, which places them one small accident away from the "mains to USB adapter cable" territory.
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