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USB inventor explains why the connector was not designed to be reversible (2019)

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Re: USB inventor explains why the connector was not designed to be reversible (2019)

#441

Post by crote »

kybernetikos wrote: post #420
userbinator wrote: post #274

Earlier quoted context omitted.

That shorts together a lot of the contacts as you're plugging it in. There are of course various devices which somehow ended up using TRRS for USB, but unplugging/plugging those while powered is definitely not recommended: https://www.reddit.com/r/ErgoMechKeyboards/comments/rt083u/a... http://www.totekinternational.com/35mm-trrs-to-usb-a-male-ca... https://pinoutguide.com/PortableDevices/ipod_shuffle_pinout....

I'm not an expert but couldn't you just make the tip live and not connect the rest until that's connected? Or have a switch for when the plug is fully inserted. I see that it's a problem for sure, but it seems easier than the problems they solved to make usb c reversible

> I'm not an expert but couldn't you just make the tip live and not connect the rest until that's connected?

No. You have to deal with disconnects being possible at both the host side and the device side. Making the tip live means you're touching a live wire to each contact in turn while plugging in the device side.

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#442

Post by eloisant »

Ajedi32 wrote: post #74
lesuorac wrote: post #13

I know everybody is still on the high from USB-C but I'm still going to go on the record it will be one of the biggest disasters in cable history. 1) There's going to be video-only cables; low-voltage only cables; etc and this time everything is usb-c so you can literally only tell which ables work by testing all of the dozen cables instead of the 1-2 USB-As you have. 2) The connector is symmetrical but the pins aren…

I had to do a double take after reading this comment to make sure I wasn't reading an old thread from 2014 or something. USB-C has been out for years now and neither of these predictions have come to pass. Your comment aged poorly before you even finished writing it. USB-C isn't without its problems, but neither of those are one of them.

Also I have to say that the situation of USB-C is much better now than in the past.

At the beginning of USB-C you had devices that were not implementing the standard correctly, and using the wrong cable could fry a device.

Now the devices are better protected, you can charge any device with any charger. Of course the charger needs to be powerful enough but if it's too powerful it's still safe to use.

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#443

Post by crote »

microtonal wrote: post #419
userbinator wrote: post #274

Earlier quoted context omitted.

That shorts together a lot of the contacts as you're plugging it in. There are of course various devices which somehow ended up using TRRS for USB, but unplugging/plugging those while powered is definitely not recommended: https://www.reddit.com/r/ErgoMechKeyboards/comments/rt083u/a... http://www.totekinternational.com/35mm-trrs-to-usb-a-male-ca... https://pinoutguide.com/PortableDevices/ipod_shuffle_pinout....

Most of this is just cheap design on part of the ergomech community. It's not that hard to add some protection. E.g. some keyboards use a Schottky diode on VCC for reverse polarity protection and ESD protection diodes to protect the data lines: https://github.com/zsa/docs/blob/master/Ergodox%20V5-L.pdf Of course the design requirements of USB would be different, since you'd always plug/yank the cable on a machine tha…

It's more an issue of ESD protection being kinda tricky on DIY boards due to the need to stick with THT parts. When you're building a $200-$300 keeb, a $0.05 diode doesn't really all that much price-wise.

ESD protection diodes also don't really solve the problem. They are intended for short-duration high-voltage low-current spikes, not long-duration low-voltage high-current ones. Definitely better than nothing, though!

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#444

Post by ikari_pl »

hedora wrote: post #278
aranchelk wrote: post #164

My take on USB-A: aside from audio connectors that have axial symmetry (and have no meaningful orientation), I never used any reversible computer cables prior to USB-C, and that’s not the main issue. Nor is it the axis of symmetry of the casing allowing failed upside down plugin attempts. The shitty part of USB-A is that the tactile feedback of being slightly misaligned is identical to it being upside down. My experi…

The best feature of those little thumb screws was that the computer-side mount could become unscrewed and fall off when you were trying to remove the cable. On some machines, it was held in with a tiny little nut on the inside of the case. The nut was just the right size to fall onto a motherboard and bridge PCB traces or exposed I/O pins. Of course, there was no way to detect this by feel.

now this sounds like you've had a terrible accident.

worst I ever had was the computer side falling out on the outside (no bolt, it was just threaded into the case itself)

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#445

Post by akerr »

somat wrote: post #345
whoooooo123 wrote: post #190

Earlier quoted context omitted.

The problem with USB-a isn't that it's non reversible, it's that it's non-reversible _and_ rectangular, so it's not clear at a glance which way round it should go. All they had to do was make the connector have a non-symmetrical shape so that it's immediately obvious which way round it goes when you pick it up - you could do it without even looking. Think of how much time we'd have collectively saved with this minor…

Right, the only thing worse than USB was the PS2 port. What sort of madness drive someone to invent a round connector that is keyed. Hyperbole aside, there are some very good reasons to go with round connectors, it can be very strong and you can put a big nut on them to have an extremely secure lock. however the PS2 connector is nether of these things, It would require a much more robust key to work well. The worst c…

I would line up the barrel and then rotate while pushing in until it plugged in. I don’t remember bending any pins. The mark on the top helped until the tower form factor turned the motherboard sideways. Still do this for XLR and MIDI but they’re more robust.

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#446

Post by crote »

snakeyjake wrote: post #140

> Making USB reversible to begin with would have necessitated twice as many wires and twice as many circuits, and would have doubled the cost. This is... not correct. You can make USB reversible with 1 extra pin and 1 extra wire. Grounds on pins 1 and 5, data on pins 2 and 4, and VCC on pin 3. Then have those pins on both sides of the plug and a socket with a single set of contacts on one side. That's BASICALLY what…

If you want to do it properly:

    1: GND/sense
    2: DATA +/-
    3: VCC
    4: DATA +/-
    5: GND/sense
Have the host side connect only pin 1 to GND and leave pin 5 floating, but have the device side connect both 1&5 to gnd, with individual pullups for 1 & 5 to VCC.

The device will sense LO on 1 and HI on 5 if either both sides are plugged in straight or both sides are plugged in reversed, but it will sense HI on 1 and LO on 5 if exactly one of them is reversed. This allows the device to detect when inversion of D+/D- is needed.

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#447

Post by gsich »

northwest65 wrote: post #84
gsich wrote: post #72

Earlier quoted context omitted.

Logo up is no help when you try to do it in the dark.

You can feel it with the pad of your thumb.

On some. But that doesn't help always as you don't know the orientation on the target device, especially when it'a sideways.

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#448

Post by crote »

dheera wrote: post #386
snakeyjake wrote: post #140

> Making USB reversible to begin with would have necessitated twice as many wires and twice as many circuits, and would have doubled the cost. This is... not correct. You can make USB reversible with 1 extra pin and 1 extra wire. Grounds on pins 1 and 5, data on pins 2 and 4, and VCC on pin 3. Then have those pins on both sides of the plug and a socket with a single set of contacts on one side. That's BASICALLY what…

Or just put + and - through a rectifier and you don't need an extra pin. Data lines -- use differential signalling and polarity determined by whether +/- got reversed by the rectifier or not. Or do like Comcast does and put all bidirectional data through 1 conductor at multi-gigabit speeds.

How are you going to implement the rectifier, though?

The usual implementation is using diodes, but that means you lose twice the diode forward voltage to the rectifier. Even with a Schottky diode that means you are losing 0.5V-1.0V. That's a 10%-20% loss at 5V!

You could use a transistor-based "ideal diode" solution, but that's not going to be cheap - especially in the 90s.

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#449

Post by crote »

oblio wrote: post #391
cyberax wrote: post #314

Earlier quoted context omitted.

That's incorrect. USB-C design maximizes the device longevity by removing springs from the device that typically get worn down quickly. The cable is responsible for the grip. You do get a protruding tongue on the device side, but it's well protected.

I broke mine on a S21. It's also getting wobbly on 2 Essential Phones. As OP said, now those 3 expensive devices are mostly broken or at risk instead of the cheap cable. It's bad design compared to the Lightning connector, and I don't like Apple...

It's not really "bad design", it's an intentional tradeoff.

Doing it the Lightning way makes it significantly more difficult to guarantee good signal integrity, especially once you get into USB 3 speeds and beyond. Not to mention exposing sensitive pins to all kinds of ESD shocks!

Re: USB inventor explains why the connector was not designed to be reversible (2019)

#450

Post by crote »

lesuorac wrote: post #13

I know everybody is still on the high from USB-C but I'm still going to go on the record it will be one of the biggest disasters in cable history. 1) There's going to be video-only cables; low-voltage only cables; etc and this time everything is usb-c so you can literally only tell which ables work by testing all of the dozen cables instead of the 1-2 USB-As you have. 2) The connector is symmetrical but the pins aren…

USB-C is actually surprisingly tricky to screw up.

For example, video-only cables are only possible if they have active electronics - so that means you are buying a very expensive cable which somehow doesn't follow the specs. I know Monoprice does make one, but it starts at $115 and it is explicitly marketed and labelled as video-only.

Low-voltage cables are the same thing. All passive cables can do 100W using 20V, and the 240W ones using 48V are explicitly marketed as such. There are some optical cables which do not transfer power at all, but again you're looking at specialized >$100 stuff. You don't just accidentally grab one of these out of your Box Of Cables.

As far as I am aware, no cable manufacturer cheaped out on the wiring because there is zero reason to. You can't simplify USB 2 cables like that, and anyone selling USB 3 cables wants all pins for it to actually be usable as a data cable.

The biggest problem with USB-C is that the USB Implementers Forum created a very clear design to indicate exactly what each device and cable is capable of - but then manufacturers decided it was ugly and just completely ignored it. If everyone just followed the damn spec there wouldn't be nearly as much confusion.

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