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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

#81

Post by fnordfnordfnord »

sharpneli wrote: post #58
nemik wrote: post #55

Earlier quoted context omitted.

It's what fuses and diodes are used for. You know how when you write a program you never trust user-input? This should be the same thing, but physically. A well-designed USB port wouldn't fry the computer like it did.

There is a limit on how much user malice should be tolerated vs the cost (additional components used, larger devices etc etc) to implement all of that. Especially as someone can always just rip the device open and circumvent all that causing breakage. How many stops there should be versus malicious usage? USB devices can handle things like the ground and voltage being shorted, as that can happen in normal use through…

Or an untrained or too-tired worker puts the assembly in the jig upside-down and pushes the button. ker-chunk. Then the worker throws the cable in the good bin because he gets paid by the kg of cables produced, and fired if the bad bin fills up.

It's 5A, they could install a polyfuse, or they could monitor the current and turn it off with a transistor.

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

#82

Post by cesarb »

josteink wrote: post #17
randallsquared wrote: post #11

Earlier quoted context omitted.

USB C is not a passive signal cable.

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…

Unfortunately for you, the exact same problem can happen with plain old regular USB; in fact, this cable had only the wires from plain old regular USB. Reversing the wires on a USB 2.0 cable would have the same effect.

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

#84

Post by qb45 »

fnordfnordfnord wrote: post #81
sharpneli wrote: post #58

Earlier quoted context omitted.

There is a limit on how much user malice should be tolerated vs the cost (additional components used, larger devices etc etc) to implement all of that. Especially as someone can always just rip the device open and circumvent all that causing breakage. How many stops there should be versus malicious usage? USB devices can handle things like the ground and voltage being shorted, as that can happen in normal use through…

Or an untrained or too-tired worker puts the assembly in the jig upside-down and pushes the button. ker-chunk. Then the worker throws the cable in the good bin because he gets paid by the kg of cables produced, and fired if the bad bin fills up. It's 5A, they could install a polyfuse, or they could monitor the current and turn it off with a transistor.

As I already explained in the previous thread about this cable, current limiting is implemented in USB hosts and chargers and it doesn't help in this case. If the powered device sinks more than 5A of reverse current, it already is dead.

For protection from reverse voltage, the powered device needs a circuit which detects negative voltage and disconnects power (which would easily consume few cm² of PCB area) or a very beefy clamping diode to shunt the negative current into ground before it reaches other circuits and pray that charger's current limiter trips before the diode overheats and vaporizes.

And even if you do that, some idiot can still make a cable which applies -5V to some data line instead of the power line, so that your whole unobtanium Intel southbridge chip goes poof. Are you going to multiply the protection circuit by the number of wires in USB3 cable and at the same time make it pass insanely fast signals without distortion?

At some point you have to give up and simply assume that cable vendors are at least minimally competent.

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

#85

Post by obelisk_ »

latj wrote: post #77
Someone1234 wrote: post #52

Earlier quoted context omitted.

> 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. T…

>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".

If engineer man does that, then he is not a good guy.

If engineer man does that, then he is a scummy asshole.

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

#86

Post by rrauenza »

obelisk_ wrote: post #85
latj wrote: post #77

Earlier quoted context omitted.

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. T…

>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". If engineer man does that, then he is not a good guy. If engineer man does that, then he is a scummy asshole.

You've mis-parsed the parent. His ...story contains an 'engineering man' and a 'main man.'

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

#87

Post by 27182818284 »

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?

Completely, no, but you can certainly safeguard. The One Laptop Per Child machines could take a reverse of positive and negative leads directly from a car battery and still be okay. The idea being that some poor kid somewhere was going to mess that up one day while trying to give it power. (Or rather I should say an EE prof told me this. I have personally not tried to electrocute any poor OLPCs)

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

#88

Post by tobz »

burgeralarm wrote: post #75
tobz wrote: post #66

Earlier quoted context omitted.

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 Schottk…

I mean, yeah, it makes sense. You can reasonably expect chargers/cables not to be quite this jacked up, and in turn, you save space in a space-constrained device. It's just a hard pill to swallow thinking that a stray cable could ruin my device like that.

(Power dissipation aside, I did manage to find some smaller Schottky power diodes that could easily handle the current. There's also the possibility of using a MOSFET, which would turn into Rds(on) * Iavg, so something like 0.15W for Rds(on)=50mOhm, which is much more manageable. I'm just a shade tree electronics guy, so I realize there was probably enough data to make a decision to forego said protection.)

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

#89

Post by Mikhail_Edoshin »

latj wrote: post #77
Someone1234 wrote: post #52

Earlier quoted context omitted.

> 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. T…

Can you make this into a movie script? :)

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

#90

Post by ThePhysicist »

cesarb wrote: post #80
ThePhysicist wrote: post #24

Earlier quoted context omitted.

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.

Point taken, but I still think that the device should be protected against supplying it with a "malicious" input voltage, as there are cheap and robust components to do this. The NCP373 for example (http://www.onsemi.com/pub_link/Collateral/NCP373-D.PDF) protects against voltages between -30 to 30 V and is designed exactly with the "faulty USB cable" use case in mind, and the low-volume cost is just 50 cents (large-volume cost is probably much lower). So I think there really is no excuse for letting a faulty 5 $ USB cable destroy your 1000 - 2000 $ device, even if it supplies an input voltage of the wrong polarity.
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