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An USB plug that goes both ways

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Re: An USB plug that goes both ways

#61

Post by thwarted »

jws wrote: post #30
marshray wrote: post #25

Earlier quoted context omitted.

What? You didn't notice the mark clearly embossed in black plastic on the black plastic background while holding it in the illuminated space between the back of your computer and the wall? Or maybe yours doesn't have a mark at all like the mouse I'm using now. Or maybe it has one mark on one side and a slightly different mark on the other. Who came up with this stupid idea anyway of making a plug that looks and feels…

Come on, it's right there in section 6.5.1 of the specification which you'd know if you searched the web, downloaded 11MB of data, unzipped it and sorted through it for the "Universal Serial Bus Specification Revision 2.0", then read all 622 pages of that. 6.5.1 USB Icon Location The USB Icon is embossed, in a recessed area, on the topside of the USB plug. This provides easy user recognition and facilitates alignment…

Come on, it's right there in section 6.5.1 of the specification which you'd know if you searched the web, downloaded 11MB of data, unzipped it and sorted through it for the "Universal Serial Bus Specification Revision 2.0", then read all 622 pages of that.

"...You hadn't exactly gone out of your way to call attention to them had you? I mean like actually telling anyone or anything."

"But the plans were on display..."

"On display? I eventually had to go down to the cellar to find them."

"That's the display department."

"With a torch."

"Ah, well the lights had probably gone."

"So had the stairs."

"But look you found the notice didn't you?"

"Yes," said Arthur, "yes I did. It was on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying 'Beware of The Leopard'."

Re: An USB plug that goes both ways

#62

Post by AlexandrB »

marshray wrote: post #38
jws wrote: post #33

Earlier quoted context omitted.

USB ports are supposed to be current limited. Given that those components cost money to buy and money to place… I think we know where low end equipment vendors are going to end up.

I'd expect current limiting to be a feature of even the cheapest USB interface ICs. It's really easy to test and potentially a short-circuit/fire hazard. Not the kind of thing any testing lab would be likely to overlook.

Funny story.

I assumed this as well - but while working on a school project I fried a very nice motherboard when our project got a short from a wire that had come loose. Lesson learned - use a separate power supply and keep the USB only for signalling.

Re: An USB plug that goes both ways

#63

Post by russell »

OK kids, quit the bellyaching. There is only one way to get a USB cable wrong, even if you get it wrong 90% of the time. Remember the PS2. It came with round DIN connectors. There was only one right way to plug it in, but an indefinite number of wrong ways to try it. And we had to do it uphill...in the snow.

Re: An USB plug that goes both ways

#64

Post by dfox »

marshray wrote: post #38
jws wrote: post #33

Earlier quoted context omitted.

USB ports are supposed to be current limited. Given that those components cost money to buy and money to place… I think we know where low end equipment vendors are going to end up.

I'd expect current limiting to be a feature of even the cheapest USB interface ICs. It's really easy to test and potentially a short-circuit/fire hazard. Not the kind of thing any testing lab would be likely to overlook.

There is probably no USB Host-side interface that really implements USB current-limiting completely. Common solution (used on Intel's reference designs) involves placing solid-state fuse into +5V line (preferably for each port) and sensing if it trips (by routing +5V from actual connector to USB controller IC). Rating of such fuse is typically significantly larger than 500mA (which is maximal allowed current). Truly correct implementation of this would have array of such fuses in different ratings and would switch them according to required current declared by connected device (I don't know of any USB controller or hub IC that actually can do this, not to mention that such thing would be order of magnitude more expensive, which explains why it's not mandatory and why nobody does that). On the other hand there are also pretty common solutions that simply do not do current limiting in any way (or have non-resettable fuse soldered onto board).

Re: An USB plug that goes both ways

#65

Post by s3graham »

russell wrote: post #63

OK kids, quit the bellyaching. There is only one way to get a USB cable wrong, even if you get it wrong 90% of the time. Remember the PS2. It came with round DIN connectors. There was only one right way to plug it in, but an indefinite number of wrong ways to try it. And we had to do it uphill...in the snow.

PS/2 connectors were actually more usable because you could apply light pressure and then without looking, spin it from side to side, and then push in when it "docked".

Re: An USB plug that goes both ways

#66

Post by moomba »

This great new product will revolutionize the way we input usb cables into our laptops. I would compare its significance to being somewhere between curing polio and ending apartheid in South Africa.

Re: An USB plug that goes both ways

#68

Post by jarek »

marshray wrote: post #37
jws wrote: post #30

Earlier quoted context omitted.

Come on, it's right there in section 6.5.1 of the specification which you'd know if you searched the web, downloaded 11MB of data, unzipped it and sorted through it for the "Universal Serial Bus Specification Revision 2.0", then read all 622 pages of that. 6.5.1 USB Icon Location The USB Icon is embossed, in a recessed area, on the topside of the USB plug. This provides easy user recognition and facilitates alignment…

"First we're gonna recess 'em, then we're gonna emboss 'em, then we're gonna mate 'em!" Designers should look to nature. Nature has certainly created some wonderful symmetries, but a symmetry which would impose hidden and unnecessary constraints on alignment during the mating process is not one of them!

This is probably the only chance I will ever get to link a page containing the words "duck penis" on HN, and you bet I will take it: http://scienceblogs.com/neurotopia/2010/01/friday_weird_scie...

Re: An USB plug that goes both ways

#69

Post by pyre »

slowpoison wrote: post #60
jws wrote: post #30

Earlier quoted context omitted.

Come on, it's right there in section 6.5.1 of the specification which you'd know if you searched the web, downloaded 11MB of data, unzipped it and sorted through it for the "Universal Serial Bus Specification Revision 2.0", then read all 622 pages of that. 6.5.1 USB Icon Location The USB Icon is embossed, in a recessed area, on the topside of the USB plug. This provides easy user recognition and facilitates alignment…

The Microsoft keyboard and mouse I have, not only have the USB symbol embossed, they also sport a raised dot to help identify the correct side. Wish more manufacturers did that. On the other hand, PC manufacturers have defeated that purpose by creating vertically aligned USB ports. Which side is the right side now? Just goes to say that intelligent specs are not enough. You can't hand a brilliant spec to a monkey and…

What is a 'vertically aligned USB port?' For that matter, what side of a computer is 'up?' Nothing is stopping anyone from re-orienting their computer in from the way that the manufacturer intended. Not to mention computer cases that are designed to be able to sit both ways. I think that the take-away here is that you don't design a connector that depends on the orientation of the device.

Re: An USB plug that goes both ways

#70

Post by pyre »

dholowiski wrote: post #40
jws wrote: post #30

Earlier quoted context omitted.

Come on, it's right there in section 6.5.1 of the specification which you'd know if you searched the web, downloaded 11MB of data, unzipped it and sorted through it for the "Universal Serial Bus Specification Revision 2.0", then read all 622 pages of that. 6.5.1 USB Icon Location The USB Icon is embossed, in a recessed area, on the topside of the USB plug. This provides easy user recognition and facilitates alignment…

In all seriousness, the USB Spec is an interesting read (I used to keep a printout of it on my desk for reference). I've pored over the physical specifications more times than I can count - it's amazing how much thought was put into this connector.

I wonder how much different things would be if a peer-2-peer protocol like IEEE1394 won out against USB and it's client-server model of bus communication.
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