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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

#71

Post by Dylan16807 »

qb45 wrote: post #70
Dylan16807 wrote: post #60

Earlier quoted context omitted.

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.

I know, but that's not a cable. You need more diligence when buying transformers, but a wire with a plug shouldn't be able to do unexpected damage.

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

#72

Post by Dylan16807 »

sharpneli wrote: post #62
Dylan16807 wrote: post #60

Earlier quoted context omitted.

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…

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

I mean that the physical object is obviously wrong. Such a cable looks like any other cable.

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

#73

Post by mikeash »

Arnt wrote: post #68
mikeash wrote: post #53

Earlier quoted context omitted.

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.

That'll learn ya.

(For the record, I didn't downvote.)

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

#75

Post by burgeralarm »

tobz wrote: post #66
sharpneli wrote: post #20

Earlier quoted context omitted.

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.

According to the engineer who tested the cable:

"Most devices with a well-specified connector will not have any reverse bias protection in them because both it shouldn't be needed and for the technical reasons of power loss and space used.

Reverse protection is usually done with diodes, the canonical "one-way valve" of electronics. Diodes have a voltage drop across them, usually 0.6V for standard and 0.4V for Schottky types. Using one of these to protect one rail means you'll have about 1W lost to heat when charging at 3A. They are also not small for the currents involved with high-speed charging, being about 7x6x2.5mm for the smallest ones I can find that can handle 3A.

Devices don't usually have too much in the lines of over current protection outside of something like a polyfuse because the device will dictate the current used; if everything is okay in the device it'll set the charging rate and it only needs the most basic of protections in the case that something goes grossly wrong with the device. Sources are what really need overcurrent protection as they don't "have a say" in how much current is drawn."

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

#76

Post by [deleted] »

Dylan16807 wrote: post #72
sharpneli wrote: post #62

Earlier quoted context omitted.

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…

>A cable that puts 5 volts into random pin is also obviously wrong. I mean that the physical object is obviously wrong. Such a cable looks like any other cable.

[deleted]

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

#77

Post by latj »

Someone1234 wrote: post #52
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.

> I suspect it's straight-up malicious Hanlon's razor: "never assume malice when stupidity will suffice." It doesn't even make rational sense for a business creating cables to intentionally damage equipment. They'd just get sued, tons of bad PR/reviews, and gain nothing obvious. More likely they just had production line issues, lack of QA, and poor training for staff. Resulted in malfunctioning equipment being sold.…

My money is on incompetence too, but it certainly could be malicious. For example, imagine a small company run by two frat brother entrepreneur guys. They bribe some factory supervisor in Taiwan for the designs to a product. They cant understand anything about it but they decide to tweak it to make it cheaper. Their greatly underpaid sole engineer discovers his girlfriend is cheating with the main entrepreneur guy. This is pretty disgusting because engineer man is a good guy and main guy has an underage girlfriend living in a plywood loft built inside a storage unit. One day engineer man says "fuck this I'm going to be a fucking farmer now". He modifies the designs to suck before grabbing a check from the middle of the stack in the printer and heads out the door. Six months later the factory in Taiwan wants the designs for the new product. Main guy digs around on the file system and finds the modified stuff. His new engineer just started and isnt really an engineer but rather an engineering student- he says he will "do the needful". Instead of looking over the designs new engineer plays rocket league and smokes weed. Another six months later engineer guy is growing organic carrots and heritage lambs with his new gf who has kind of fucked up feet and not great teeth but she's nice to him and is good at farm chores. At night he goes to read /r/girlsgoodatfarmchores and at some point sees a link to a video of a cable frying the shit out of the thing its plugged into. "Huh, I really ought to clean this shit out from under my fingernails" he thinks.

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

#78

Post by cesarb »

Vendan wrote: post #46
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.

well, usb type C is supposed to have at least 9 wires, if I recall correctly. This is not a valid type C cable, but it was being sold as one, which is part of the outrage. (aside from the "killing devices" bit)

A "USB Type-C to USB 2.0 Type-A cable" has 4 wires (same as any USB 2.0 cable, really; only the plug in one end is different).

The problem is that this was being sold as a "USB Type-C to USB 3.1 Type-A cable", which is supposed to have 10 wires.

(A full USB Type-C cable has some 18 wires, since it wires both sides separately so the alternate modes which use both sides separately can work.)

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

#80

Post by cesarb »

ThePhysicist wrote: post #24
josteink wrote: post #10

Does anyone else find it concerning that our new and best technology is so fragile that even the slightest fezz-up in what should be a passive signal-cable can cause our otherwise state of the art equipment to fry itself? Is reliability, durability and robustness nowhere to be found in any single spec for our new standards?

I would say that the Chromebook's USB ports are probably to blame as well. Shorting the +Vpp pin to GND should only result in sinking the maximum current but not in the port being damaged. Likewise, I'd expect the signal port to be protected against shorting it to GND or connecting it to a (moderately) high input voltage. The USB standard does probably not require these kind of protections, but they are nevertheless…

This was not shorting +Vpp to GND; this was putting -Vpp in the +Vpp pin. All pins are referenced to GND, which is 0V by definition, so if you put +5V in it, it's the same as subtracting 5V from the voltage in all the other pins. And since they put the 0V in +Vpp, it became -5V. Most devices aren't prepared for negative voltages.
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