HN has previously had a story on the author, a Google engineer who tests USB-C cables on Amazon to make sure they're spec-compliant. He does some amazing work:
I don't have any devices right now that use USB-C, but whenever I see a deal pop up for one, I usually check the Amazon listing to see if this guy has reviewed/certified the cable yet.
I recommend others do the same. It's not worth damaging your $800+ laptop because you wanted to save $10 on a cable.
Does it matter? As someone that has hunted for cables reviewed by Benson I really wish I had known about this website. They are both providing a service.
It's worth noting that the Nexus 5x doesn't do USB 3.1, so even if you get a fancy Super Speed cable like this one, you are still suck with slow charging from your computer's USB A port.
The Nexus 5X supports the new 15W fast charging USB-C standard . It takes about 15-20m for my phone to go from empty to full from the wall charger, and considerably longer from a USB A port.
I think something is broken on mine then. It takes an hour and five ten minutes to go from 15% to full from a wall charger. Are you sure it only takes 15-20 mins?
Second data point. Mine takes about 35 minutes to go from near empty to full if I use the supplied wall charger, and is substantially slower if I use most other things (though oddly, my Anker DC->AC 2-port USB-A charger is able to support rapid charging).
When you plug it in, turn it off, then back on. Down at the bottom, near the fingerprint, it should indicate the type of charging you're getting. I've seen three modes, and I apologize for not knowing the distinctions, but they're "charging slowly", "charging" and "charging rapidly".
Times are commensurate to the charge mode, and rapid charging is unsurprisingly quite fast.
Another thing that might be the case is if the OP is going from actual empty to full without turning it on, which should (to some extent) expedite charging as there is no discharge happening at the same time, maybe.
It does, from a USB C cable. Unfortunately, the fast-charging protocol for USB A (USB Battery Charging 1.2) needs a USB 3.1 controller, which the Nexus 5x doesn't support; hence, the slow charging with an A -> C cable, even if it's a 3.1 SuperSpeed cable.
Each cable needs one of 3 resistors depending on them being a A/B-to-C cable, 1.5A C-to-C cable, or 3A C-to-C cable.
Note that the A-to-C cable may well be able to carry 3A, but it shall never use the 3A C-to-C resistor (what many of the cables he find as faulty does).
Note that all this resistor shenanigans are all independent of the Battery charging spec that has been around for some years, and also the Power Delivery spec that was introduced along with the 3.1 USB spec (can be used for all ports) and the C port spec.
Never mind that a C port has so many extra pins compared to a A or B port, that one would think that id-ing a A-to-C cable would have been as simple as looking for life on any of those extra pins.
> Each cable needs one of 3 resistors depending on them being a A/B-to-C cable, 1.5A C-to-C cable, or 3A C-to-C cable.
No, for C-to-C connections, the resistance is provided by the host ("downstream-facing") port, not the cable. The resistor in an A-to-C cable is basically emulating the signal that would otherwise be provided by the host.
There's no such thing as a "1.5A C-to-C cable"; all type-C cables are required to deliver at least 5A. The limiting factor is the host, not the cable, which means the cable must not incorrectly advertise capabilities that the host doesn't support.
> Never mind that a C port has so many extra pins compared to a A or B port, that one would think that id-ing a A-to-C cable would have been as simple as looking for life on any of those extra pins.
That's exactly what the new CC pin is used for. Right now the spec says "legacy cables should connect CC via a 56kΩ resistor", but it wouldn't matter if instead the requirement had been "legacy cables should leave CC disconnected"; the issue is that cable manufacturers are ignoring the spec.
USB cables aren't smart cables by any stretch of the imagination—not when we've got standards like Thunderbolt. A single resistor is not unreasonable complexity on top of the requirements to get the pinout correct.
> There's no such thing as a "1.5A C-to-C cable"; all type-C cables are required to deliver at least 5A.
1.5 A is required to be supported by USB-C, while 3 A is optional. Everything over it is covered by USB Power Delivery, which requires a marking of the cable which of the 5 profiles are supported.
After re-reading the spec, I think both your comment and mine are slightly wrong. Connectors must be capable of handling 5A; cables are required to support at least 3A. (See sections 3.1.2 and 3.7.7.4.) You're correct that higher power requires USB-PD.
USB-C does lots of things, including high voltage charging, backwards compatibility, and reversible orientation. Yeah, you could make it simpler, but then you'd have to start giving up some of those features, at which point now you've just reinvented USB-A again.
It's just as complicated as it needs to be. And for godssakes, the pin-out diagram isn't that complicated; it only has 24 pins! There's no excuse for flipping two of them. 24 pins is not beyond the pale of what we would reasonably expect manufacturers to be able to wrap their heads around.
Have you read the spec on what it actually allows though? The fact that it can do USB 2.0 + USB 3.0/3.1 SS + AltMode + 100W Power (bi-directional) all at the same time is... impressive.
To be fair it's really 12 times 2 to allow the cable to be reversible. USB2 had 4, USB3 had 9. Apples to apples you should compare 8 and 18, but the previous two standards weren't reversible.
Oh christ... Those pins are actually different signals? When I bought a nexus phone and looked at the new connector I assumed they were just trying to use tricks to reduce contact resistance or something.
Well, the USB 2.0 pins are mirrored so there is no negotiation needed to orient the plug. The others can be mirrored or not, depending on how it is operating. Negotiation can change the job of several sets of pins.
If you're using the plug to do USB, you only use the pins on a single side. It's also possible to use DisplayPort and USB 2.0 with the pins on one side.
You use the pins on both sides to do four-lane DisplayPort, or DisplayPort and USB 3 at the same time, or Thunderbolt.
TL;DR; USB-C cable had GND tied to Vbus and Vbus tied to GND (opposite as it should be)
Honestly, I'm surprised that this isn't something that thelaptop and other such USB adapters aren't equipped to deal with. This is only slightly worse in my book than a USB adapter being fried from shorting the Vbus and GND pins together
That's worse than a short. A short pulls the Vbus to 0V, leading to high currents on the source, so whatever overcurrent protection it has kicks in. What he had here, instead, was -5V on the Vbus pin, way outside the acceptable voltage range (which is probably something like from -0.5V to 5.5V). It's no wonder everything fried.
The protection against reversed voltages like that would be a crowbar diode between Vbus and GND, to convert the negative voltage into a short circuit. But even if it had that reverse protection, if the current was high enough (since the negative voltage was from a charger, it's not unlikely) the diode could burn open, and then you have negative voltages again. And I don't know how common these crowbar diodes are; they probably are rare, since the USB connector is keyed so it can't be plugged "backwards" (the type C connector is mirrored instead, either orientation connects the pins the right way).
From what I understand, a crowbar diode is a reverse-biased diode put in parallel with the bus, not in series. In normal operation (correct polarity) it doesn't conduct, since it's the "wrong way", and there's no voltage drop since it's not in series with the circuit.
But when the polarity is reversed beyond the diode's voltage drop (that is, beyond -0.6V in your example), the diode is now the "right way" and conducts, limiting the reverse polarity voltage to the diode's voltage drop (in your example, it won't get below -0.6V).
However, that means that all the reverse-polarity current goes through the diode, in effect a short (like putting a physical crowbar across the battery terminals). If the diode holds long enough, the voltage source's short-circuit protection (be it a fuse, a polyfuse, or something else) should cut the current and all is (mostly) fine.
Electrical faults are just a fact of life. Wires fray, cables get tugged, or are miswired from the factory. And you just know that sooner or later some genius is gonna jam a butter knife in there for the hell of it.
The basic USB spec requires that all ports be protected with a small self-resetting polyfuse for exactly this reason. I don't know if the Type-C or USB 3.1 specs includes something similar - I would assume so but perhaps the additional current capabilities made that infeasible.
A standard USB polyfuse usually resets pretty fast (as soon as it cools down) but they could take up to a few days. It's also possible the manufacturer cheaped out and didn't include a polyfuse, of course.
I found a USB Cellular data adapter in the trash and plugged it in to my MacBook Pro, which instantly shut down.
Rebooted, and the USB port did not work. Shut it down and left it for half an hour, and, yay, all working again.
Disassembled the adapter. Turned out to be a dummy used for display. No guts, just a steel bar across all four pins of the USB connector. Looked real from the outside.
It was a very, very stupid thing to do. Thank-you Apple for putting a self-resetting fuse in my MacBook Pro. Saved my idiot butt.
Plugging random USB devices into your computer is a bad idea, full stop -- miswired or not. "I found this in the trash and plugged it in" is the bane of CISOs everywhere.
This was an A-C cables, which means it was used to charge the laptop, not to power something from the laptop.
Current limiting doesn't magically protect powered devices from voltage reversal (-5V instead of +5V), so both the laptop and power delivery analyzer went poof.
They may have taken enough current to trip charger's current limiter, but then it was a bit too late.
Why would you design in reverse polarity protection? It adds cost, and the mechanical connector already makes it impossible for VDD to short to GND in USB type C because of its rotational symmetry.
I constantly have Vdd shorts due to ground loops when measuring stuff. But a more frequent case is worn out cables (every lightning cable I've owned has eventually broke).
Yes, and that's why the USB spec puts the burden of protecting against electrical shorts on the controller. The device side shouldn't have to worry about trying to shunt 100 Watts of power somewhere.
I mean this kind of protection is way beyond typical ESD protection due to the power involved. It would add a lot of cost to do this, maybe even a dollar or two in raw material.
I don't want to be a broken record, but you're right, not a tall order, but no it's unreasonable on account of cost. It's impossible for USB C to be hooked up backwards by its mechanical design, so why guard against it? The high-side transistor to prevent reverse polarity faults could be 3 to 4 cents in manufacturing cost! It's also not trivial to make sure that transistor trips fast enough to prevent all your low-voltage ICs from being destroyed.
Most likely cheap consumer devices wouldn't get it, but prosumer, enterprise and industrial gear should think twice about cutting corners on peripherial protection circuits and make sure to test vcc ground reversal and application to data pins... because commercial engineering boils down to risk management.
> t's impossible for USB C to be hooked up backwards by its mechanical design, so why guard against it?
Because cabling can fail in other ways. A short could be caused by mechanical damage to the cable anywhere along its length. It would be nice to have a host that doesn't burn up in those scenarios seeing as they are already required to protect the bus.
Like other comments have mentioned, a short is not a voltage reversal. The methods to alleviate them are different. As the connector is polarized, the only way to get a voltage reversal is for something seriously strange to happen either at the power supply end or the cable.
If it is at the power supply end, all bets are off. If your USB charger fails short prepare for mains voltage to absolutely fry anything and everything connected to it and a negative voltage is the least of your worries. In the cable, a miswiring is seriously negligent and I see no reason why it should be designed around.
Sure, but the magnitude of that cost matters a lot. You were saying a dollar or two in raw materials to protect against 100W, now you're saying three or four cents. A few cents to protect hundreds of dollars in equipment from electrical faults seems worthwhile to me.
That makes sense from the consumer's point of view. But imagine you're a manufacturer, producing USB device controller chips by the million. Would you really be willing to spend tens of thousands of dollars to protect against a failure mode that can only happen due to some other company's extreme negligence?
Yes, but of course it doesn't matter what I think.
It's not abnormal to add protection that isn't needed when everything works properly. As noted elsewhere, the USB spec already requires resettable overcurrent protection, for example.
I see! A dollar per port for robust protection against a wide variety of faults sounds pretty good to me, but I know that sort of stuff doesn't sell well when people compare primarily on price.
Do I assume correctly that a fuse for overcurrent protection wont act quickly enough to save the hardware in the event of reverse polarity?
Look for a long response near the end of the article comments, from Mike Crawford. It goes into detail as to why that protection isn't designed in - it's not cost (diodes are cheap), but power drop, which has side effects.
I was playing with a FTDI (a clone :D) and an Arduino and accidentally mixed up VCC and GND from an external power source. I only realised because Minicom was failing to connect to the device. Then I realised what I had done, I tried removing it from the USB port and putting it back in, but it wouldn't work. I then tried a mouse too, but that wasn't working either. Thinking I'd killed a USB port on my Mac (well there are two, so...) I then tried rebooting and that fortunately fixed it.
If you're doing lab work, it's really easy to get weird potentials on various lines. I almost never plug anything like an Arduino directly into my laptop without a powered hub in between.
I assume I'm a klutz. So, I take steps to minimize the damage when something happens.
Anyone have a hub to recommend? I have a hub which I bought for cheap on eBay which I use on my desk for keyboard, mouse and similar but would not trust that hub to offer much if any in way of voltage protection so I'd like to know about safe hubs for lab use.
USB overcurrent protection is pretty sophisticated. Devices get 100 mA for free, then have to ask the host for more current. Well, it's a bit more complex nowadays, but that's the basics.
I'm not sure if there are many devices which actally follow that spec to the letter (in either direction). Usually the USB ports will just allow 500mA (or whatever they're designed to provide) plus some fairly generous overhead, regardless of what the device has asked for, and assuming they bother to implement overcurrent detection at all.
Yep, did almost exactly this, shorted a converted 3.3V from a different USB port (same machine) to ground on a different USB port and end result is my motherboard lost all USB connectivity until I rebooted
I wonder if this one cable was miswired or it's something consistently wrong with the product. Either way that something like that could make it out of the factory demonstrates terrible or no QA/QC.
I've never used the Twinkie but it looks pretty cool. This shows that it may be worth adding some simple protection to the circuit to prevent simple miswires from damaging it or the host PC.
The question isn't what was wrong with the cable, but whether it was just this one specific cable, or whether it's all of the cables in from this production run.
For those unfamiliar, this person (Benson Leung) is a Google employee that has been testing USB-C cables to make sure they match the specs. His efforts were previously discussed on HN[0].
Reverse polarity protection is often not done with diodes for the reasons explained. It is more common to use a p-channel MOSFET (or ideal diode controllers when there are multiple power sources) when more than a trivial amount of power is used by the design. They are not cheap when properly sized, but are not ruinously expensive either and are not too large for most designs.
Doing the math, a reasonable PMOS might be the Si2323, although it can only handle ~5A. Costs $0.20 in quantity. Therefore, on a $500 laptop, don't bother if it doesn't save you more than 1 in 2,500 laptops. That is, assuming that you are only trying to save the company money, not make a reliable product. PR can always blame the faulty cable / charger.
Crowbar isn't a diode, and it doesn't protect against reversed polarity, and it's a bad idea on the input because you're relying on the other device to limit current properly, when it's the other device which got the voltage wrong in the first place.
It acts like a literal crowbar, so why not call it a crowbar?
There are likely already plenty of diodes across the rails (the body diodes of the chips), so without a fuse the power is already limited by just the source. IMHO you might as well try and protect the circuit from foreseeable power-limited situations like frayed cables and the OP.
I'm saying a crowbar isn't a diode, and you're saying that you should call a crowbar a crowbar? Color me confused. Usually a crowbar is a circuit with a triac or SCR in it designed to protect against overvoltage.
This isn't about frayed cables. Frayed cables don't do this. This is about a cable which is wired the opposite of the way it should be. A minimal protection circuit is probably going to cost around $0.20 in quantity (Si2323 on Mouser). For a $500 Chrome Pixel C, the protection circuit is worth the effort if more than 1 in 2,500 ($500 / $0.20) laptops would fail due to charger cables with reversed polarity.
If you think that fewer than 1 in 2,500 laptops will fail this way, then don't bother.
Crowbar is a general concept - a short across a supply. A diode across the rails acts as such, so I referred to it as a crowbar. I'm familiar with SCR-based active crowbar circuits - what we're disagreeing about is narrow-prescriptive versus wide-descriptive usage of a term.
Most frayed cables are going to simply short or open, but the right combination of such would cross wires. But sure, they're going to be rare.
On a $500 device I would indeed expect a modicum of robustness against negligently designed cables and other weirdness. I mean, I'm not the only one that doesn't have a cable tester and buys cables without a connected-equipment warranty, right? Historically, electrical connections have been designed to deal with weird shit. Do you think you could kill an RS-232 port with any permutation of connections?
Of course the cost metric explains why devices are no longer robust. In fact the manufacturer only has to worry about in-warranty failures, and furthermore only the ones they can't blow off as "user error". Just because devices are designed for the 4 month (or whatever it's down to) upgrade cycle, doesn't mean that informed consumers shouldn't call out designers of such equipment as the cheapskates they are!
Ugh. Am I the only one who appreciates cheap things for what they are? Over-engineering something is a bad thing, just as under-engineering it is too. It makes things more expensive than they have to be.
There's an art to designing something to last for no longer than it has to, and to use not a single part that isn't necessary. How much worse would our lives be if we had to pay industrial/commercial prices for all of our goods?
I think at some point Amazon should take some heat. They should at least de-emphasize uncertified cables or require vendors to have licensed the USB logo.
If you buy a power strip, even a cheap one, you at least get some assurance that it is UL rated and probably won't burn your house down. USB isn't just a keyboard connector anymore... We should have some assurance that cables are legit and safe.
Amazon in Germany happily sells you power strips / connectors you can't use in Germany without effectively voiding your insurance if your house burns down (e.g. T-connectors that let you connect two Schuko plugs to a single wall outlet without a cable).
Granted, for some of them it adds a small disclaimer "Only for export" but let's be honest: if you're selling to consumers, you're not selling for export.
Seems to be a kind of bait-and-switch operation, see this G+ comment by Lance Nanek:
>>It's pretty common on amazon for some good items to be shipped to get some good ratings, then for the seller to replace them with cheap, almost non-functional, shoddy replacements. It's happened to me before with bicycle equipment (pushing the button on a rear light pushed right through the casing, etc.). So it's entirely possible you got a good one from their initial offering, then they started selling something else.<<
> These are the wonders of globalization. USA consumer protection laws don't apply to foreign manufacturers using noname brands.
That's false if you buy stuff on Amazon. That's true if you buy goods on a chinese website. USA consumer protection laws certainly apply since Amazon is a US corporation. Otherwise Amazon would be selling controlled substances like it's an Rx.
Interesting that most of the reviews for Anker and Aukey products on Amazon have a variation of the same "I was provided with a free sample of this product in exchange for my unbiased professional review."
How on earth do you think the tech review industry works? 99% of the reviews you've read utilize free gear provided by the vendor. Some publications have taken steps to curb potential excesses, but at least when I was freelancing (2000-2005), almost all writers were provided gear for free, and allowed to keep said gear.
Ethical journalists can attempt to ignore the impact of gratis equipment, but it's difficult in the best of situations. Just as difficult as trying to ignore the impact of a "helpful" PR department. Apple was particularly good at this; I was provided with every version of the iPad for reviews. Once Apple got over their death march, this dried up, and dealing with their PR firm became tedious. HP provided notebooks, PDAs, anything, with no expectation or real system for returning equipment. The only vendors I ever dealt with that were strict about returns were Kodak/Canon with their DSLRs and lenses. These were normally around $10K or greater, so I was not surprised at all.
Bias is implicit in any review where the publication isn't purchasing the items it reviews. I'm not sure how Sweethome and the Wirecutter work, though I know they make $$ off of purchase referrals through Amazon.
There's a big difference between giving review samples to journalists to review and publish on their own sites, and giving samples to be reviewed in bulk on Amazon in the same context of customer reviews and aggregated together with the same scores, with only a footnote of disclosure. Getting review samples isn't the problem; the reviews are just being published in the wrong manner. It's particularly inexcusable that the reviews solicited in this manner are eligible to be tagged as "verified purchaser" reviews.
The "Verified Purchaser" tag is just so that people know the reviewer actually received and ideally evaluated an actual unit, as opposed to a sockpuppet review. What's your issue with his review? He actually reviewed the actual units, compared them to the specs, and gave his professional opinion. All in a place where it can do the most good, as opposed to posted to some defunct Google blog.
I think you lost track of the context. Benson Leung's reviews aren't the ones including the disclaimer; he probably is spending his own (or Google's) money to actually purchase the products. This is different from the astroturfing spammers whose reviews are tagged as "Verified Purchaser" but the text of the reviews shows that they didn't have to actually purchase the product. Those spam reviews are rarely anything but vacuous and are certainly not professional opinions in the same sense as Benson Leung's.
That seems to be the trend lately. Most of the reviews are polluted with this SPAM now. Amazon Vine is an AMZN sponsored program to enable this.
I had a similar issue with a lightning cable purchased on Amazon that claimed to be a licensed Apple cable, but wasn't. I plugged it into a real Apple charger, went to plug the other end into my iPhone and sparks flew out of it as soon as it got close to the phone.
Do you mind explaining why? Short circuits are common, and are mitigated against. Reversed voltage is exceedingly rare, especially for USB C with mirrored contacts.
The purpose of test equipment is to diagnose weird situations - hence why OP broke two of them trying to understand what was happening. Its requirements are to be as robust and transparent as practical. The other end of the cable could likely be bare wires connected ad-hoc with alligator/mini clips.
FWIW because the USB PD device is connecting two separate grounds, this same failure could have happened from a single broken ground wire.
> The purpose of test equipment is to diagnose weird situations...Its requirements are to be as robust and transparent as practical
That doesn't set a clear-cut boundary, does it? What seems practical to you might be impractical to the test equipment maker - especially when cost is considered. Should the test equipment be robust enough to handle 1000+ amps? I'd say no, someone else (maybe even you) might say yes.
Killed a laptop when plugging in my phone (with the old 30 pin connector). Turns out a bit of foil from a wrapper had become stuck in the slot on the phone.
Since this was in the bad old day the laptop was fixable for under $200 so it wasn't too bad.
Still, makes sense to keep an eye on what you plug into your computer.
You can find motherboards and other components on eBay. http://www.laptopinventory.com/ has a very good catalog and excellent how-to videos. I have done parts replacement on a few of my laptops (screens, keyboards, touchpads) and if you have ever added RAM to a laptop the process for the other components is not really any different.
from what i remember, it was not his job -- he worked on products that have usb-c components (like the pixel laptops) and wanted to make sure the products on amazon were up to spec. you can see his reasoning here: https://plus.google.com/+BensonLeung/posts/LH4PPgVrKVN
Definitely not, I would buy cables that had already been reviewed by a very thorough user like him! But this guy has made it a hobby to buy different USB 3 cables and try them out. If I was doing that, I would have made a continuity check test rig to measure point to point and also measure the pullups that he usually ends up measuring by hand.
He's a Google employee, presumably using corporate hardware to advance the USB C ecosystem that the Pixel line is shepherding. I'd be shocked if Google didn't let him replace it.
Full disclosure: Not a Google employee, not even a fanboy anymore after some of the stuff I have seen over the last few years. That said I'm FED UP with this Google+ bashing.
Two major annoyances: no api access and centralized. Otherwise nice. Have used it a lot, but not much lately.
Generally it seems to be nicer and more focused on topics than twitter.
USB-C seems like a really bad standard if the cable can destroy expensive electronics.
EDIT: Even if the cable is wired and built correctly (which is apparently difficult for manufacturers to get right), cables fray and tear all the time. I foresee a lot of dead electronics upcoming.
It's not USB-C. The same thing would happen with USB-A/B, or any other standard which provides power with a well-defined polarity. The mistake was in the simplest part of the standard: the pair of wires which carry the voltage reference (GND) and the main voltage (Vbus), a pair of wires which exist since the original USB standard, and in many many other standards (ever used a "PS/2" keyboard? guess what, two of the pins are GND and Vbus!).
As for cables fraying, the most common result is an open (an unconnected wire). If two of the wires get damaged at the same time, you might get a short (and the USB standard mandates that a short causes no damage to devices). But reversing a pair of wires? It's ridiculously unlikely that fray and tear on a cable not only severs a pair of wires, but also reconnects them backwards!
That's like saying Ethernet, VGA, and many other standards are bad because http://www.fiftythree.org/etherkiller/ shows cables that directly pump AC power into them.
https://news.ycombinator.com/item?id=10508494
I don't have any devices right now that use USB-C, but whenever I see a deal pop up for one, I usually check the Amazon listing to see if this guy has reviewed/certified the cable yet.
I recommend others do the same. It's not worth damaging your $800+ laptop because you wanted to save $10 on a cable.