USB "Condom" Allows You To Practice Safe Charging 208
MojoKid writes "Yep, a USB condom. That term is mostly a dose of marketing brilliance, which is to say that grabs your attention while also serving as an apt description of the product. A little company called int3.cc has developed a product—a USB condom—that blocks the data pins in your USB device while leaving the power pins free. Thus, any time you need to plug a device such as a smartphones into a USB port to charge it—let's say at a public charging kiosk or a coworker's computer--you don't have to worry about compromising any data or contracting some nasty malware. It's one of those simple solutions that seems so obvious once someone came up with it."
You can do this with a USB extension cable... (Score:4, Informative)
I've made my own, but you can buy them inexpensively. They're really convenient if you're, say, trying to keep devices from popping the VMWare Fusion Mac/Linux selection dialog or complaining about ejection.
So, yeah, this guy made a board, but a cut-line extension cable has been the answer to this problem for a while. Some devices may fuss or trickle charge, but it generally works.
Re:Fast charge detection (Score:4, Informative)
Actually you have been able to get "charge only" USB cables for years, and they fully support fast charging too. To enable 1000mA charging you just tie the D+ and D- lines together, so the charge only cables simple cross the over. Data comms fail but charging works fine.
I bought a couple last time I was in Japan, and assume they will become available in the west eventually.
Re:*yawn* these have around for years? (Score:5, Informative)
"Negotiate" is a loose term - really it's just some fixed resistances across the data pins that set USB charging mode. This can be built into the plug without any extra copper in the cable.
For dump power supplies, it's "just some fixed resistances" between data pins. That's a shortcut for chargers that don't want to implement the USB protocol.
Computers, however, do use the data lines for the intended purpose. With computers, the amount of power that can be drawn is negotiated between the computer and the devices.
Re:*yawn* these have around for years? (Score:5, Informative)
Depends upon device/manufacturer. Some use fixed-resistance, but there's no agreement upon which resistance indicates which current. Others use a true computerized negotiation, but again there is no common protocol - and some manufacturers use that negotiation as a means to lock-out third party chargers by deliberately not disclosing the protocol, or even using cryptographic authentication.
Re:What the unholy crap???? (Score:4, Informative)
The photo seems to be of this thing [int3.cc], which is an entirely different device which apparently 'allows a computer (or "host") to masquerade as a USB "device" to communicate with other USB devices or USB Hosts.'
In other words, exactly the kind of device you wouldn't want to unknowingly connect things to.
Re:*yawn* these have around for years? (Score:5, Informative)
Re:*yawn* these have around for years? (Score:5, Informative)
That said for the portable device on the other end to recognise charging mode it also needs to see some fixed resistance, which would need to be build into the far end plug too.
Samsung's charger for the Galaxies simply shorts the data pins. (No, not the cable. The charger.) They do it as a way to recognize that it is a charger connected and allow drawing more power.
Re:*yawn* these have around for years? (Score:5, Informative)
[sigh] So much for "Universal".
Re:Huh? (Score:2, Informative)
I had a boyfriend with a motorola phone... it absolutely REFUSED to charge if connected into an intelligent host, unless their special software were installed. It was a total pain in the butt...
Re:*yawn* these have around for years? (Score:5, Informative)
For compatibility purposes, though, all kinds of attempted power draws that are off-spec but below whatever the device considers dangerous are generally well tolerated. USB HDDs drawing ~800ma, or connected to the data lines of one port and the power lines of a second port, little fans and LEDs on goosenecks, all kinds of nasty stuff. Especially on desktops, where +5v is available in nigh-unlimited quantities. Laptops and routers and things, with actual power budgets, seem to be a bit pickier.
Re:*yawn* these have around for years? (Score:5, Informative)
The host power lines are usually protected by a "polyfuse" (aka self-resetting fuse), sometimes just one for all lines combined if the total current is no danger to the traces should it be drawn from one port. A polyfuse is a (normally small) resistance which is designed to go into thermal runaway when the current limit is exceeded. After a few minutes without current, the fuse "resets", i.e. it cools down sufficiently for the resistance to drop far enough that the normal current won't trigger the thermal runaway.
Re:*yawn* these have around for years? (Score:5, Informative)
Actually there is a standard, laid out in the USB Battery Charging Specification [usb.org]. It clearly states that a dumb charger should short D+ and D- directly to indicate that it can supply up to 1.5A.
The only company that uses resistors is Apple. The USB spec was released in 2007 so maybe their early devices pre-dated that. In any case, any properly designed USB device from the past 5 years should fast charge from a dumb charger simply by having the D+ and D- lines shorted.
Re:*yawn* these have around for years? (Score:5, Informative)
Is there some term that is used to distinguish connectors with / without this functionality, so I can buy the right kind?
I gave up on finding USB Charging Specification-compatible chargers a while ago and just picked up a "charge-only" USB cable [amazon.com], which does the same thing as the adapter in this article: short the D+ and D- pins on the device side. This lets any standards-compliant (i.e. non-Apple) device know that it's safe to charge at full speed, so it should fix the problem so long as your charger can handle the current.
You can tell whether an Android device is charging properly by looking at the Battery pages in Settings. It should say "Charging (AC)" to indicate a full-speed charge, or "Charging (USB)" to indicate that it's limiting itself to 100mA.