Not same ability to suicide, because you can’t plug the ends into the wrong devices. Just like a normal power extension cord isn’t a suicide cable, because you can’t plug both ends into wall sockets.
As I have showed, USB-B can carry power too. It is literally just a different shaped connector. See above. Same wires end-to end. Rectangle or square (near enough). Same thing. USB-A is on the other end…where do you think that power wire goes?
OK, let’s start at a lower level. Do you understand why power cords with prongs at both ends are a bad idea? And why normal extension cords aren’t a bad idea?
Why can’t peripheral manufactures deal with USB-A? They do USB-B but literally have the eaxct same inputs. They can’t wrap their collectives heads around USB-A but can make the exact same (apart from shape) USB-B plug work?
Rectangle or square yet you all want to say it is an important difference. Why? Look up the wiring scheme for yourself.
As stated multiple times here in different ways, the wiring scheme has nothing to do with it. USB-A shaped sockets provide power and act as hosts. USB-B shaped sockets never provide power and never act as hosts.
The extension cord analogy here is perfect. One side of an extension cord is only meant to plug into a power source. The other side is only meant for a device that receives power. Just like USB the wiring is the same. But the shape of the connector limits a user from doing a dumb thing.
A device with a USB-A socket is always a host, or should always be per the spec. The connected devices always get USB-B. Either full size, micro, or mini.
Perfectly said there @Pork_Rind ! You beat me to it.
Here’s a parallel explanation I’ve had simmering for a bit, but wasn’t on my PC to write.
Here is a typical PC 110v power cord:
You’ll notice the two ends are different. Why? After all, it’s just 3 dumb wires carrying power; not even data.
It’s because the designers don’t want you to take a cord with two male ends on it and plug that into two powered wall outlets. Bad things will happen. So they don’t make cords like that. They sure as heck don’t supply cords like that with PCs.
They also don’t want to make cords with two female ends on them. Because then some goofball would plug two PCs together with that cord and wonder why they don’t both work.
The physically different but electrically identical ends are to moron-proof the hookup. Nothing more complicated than that. Back in the day when adding intelligence to the cable or to the dumb device end would have been prohibitively expensive and/or bulky.
The traditional flat USB-A connector and the square USB-B connector are exactly the same idea. When only A-B cords are made, and all devices that supply power are designed with A connectors and all devices that consume power are designed with B connectors, then the entire ecosystem is idiot-proof. If the big clunky plugs and sockets mate mechanically, the power & data arrangements will be correct also.
It’s no deeper than that.
Now after that, of course the Chinese quickly realized they could make shit cheaper by ignoring the standards and everybody else would be dumb enough to buy non-compliant parts. Then USB3.0 got invented, and USB-C and all the rest. To the point that USB-C is now almost more of a battery charging standard than it is a data transmission standard. Almost.
But all of that is just distraction from the basics of the original flat A connector and square B connector designed to prevent plugging stuff together wrong.
Which can absolutely be done with USB-A. The manufacturer decides which pin does what. USB-B still has that power power wire as does USB-A. If they can ignore it in USB-B then why not also USB-A?
4- pins A & B. Both sides.
Easy-peasy.
It could be done with A, yes. But it would be idiotic to. For exactly the same reason it would be idiotic to make both ends of a power cable the same.
Once again, as stated multiple times here if you have USB hosts and clients using the same connector, you eventually end up where someone can connect two hosts together, either backfeeding power or simply frying the port. The entire purpose of the different connectors per the spec, is to prevent that from ever happening.
I’m curious about this. I have a portable battery. If I plug it in it charges (via USB-C or USB-A).
If I connect it to a device like my phone if charges the phone (via USB-A --C or C – C).
Nothing blows up. I never need to “tell” it what is happening. It just automagically knows.
The battery is at least ten years old. Still works great.
ETA: I checked…seven years old
And the standard we’re discussing is 30 years old. And greatly predates every item you just connected together. The cable, the devices on both ends, all of it.
Right, your portable battery pack can do that, because it’s new, and they eventually figured out how to make devices smart enough to do that. Eventually. They didn’t have that when USB was first invented. A portable battery pack from the early days of USB would have to have had two different sockets, one to charge the battery, and one to use the battery to charge other devices.
And it is literally the same as USB-A except for the plug shape but no one addresses that.
It is the same…exactly the same.Yet we are to believe we would kill ourselves if they were not different.
Exactly. At some point, people, realized that people were, despite the designers’ best intent, going to build non-compliant devices and cables and send them out to unsuspecting users. So through advances in serial bus microcontrollers and what not, there’s now some rudimentary power protection in many, but not all devices.
If that battery mentioned just above really does charge over the USB-A port, then the designer fucked up. It absolutely isn’t supposed to do that.
What?
I have addressed that. @LSLGuy has addressed it. At least two or three other posters above have also addressed that but I can’t scroll that far up in preview. Just because you do not like the provided answers do not make those answers any less correct.
I addressed it too. And provided a graphic. 4-wires. 1, 2, 3, 4. The ONLY difference is the plug shape.
What else is different?
Better, tell me what changes between the USB-A plug and the USB-B plug at the other end.
Jesus Christ on a pogo stick! Yes! Exactly correct! The only difference is the connector for the exact same reason an extension cord has different connectors on both ends. So you don’t plug the wrong things together!
In post 146, @LSLGuy posted a picture of a standard power cable. Two power conductors and one ground conductor, not even any data. Just three wires running straight through. Even though they could have made both ends of that cable the same, they made them different. Do you understand why they did that?
It’s not the USB cable wires that matter; it is what is connected to those wires on each side.
The extension cord analogy is not working – so think of a typical garden hose. It has 2 different connectors so that you can only ever hook up 1 input source of water and 1 output source of water. You don’t ever want to connect two taps or two sprinklers, that would be useless.
Going back to USB, if it helps, you should know that the 4 wires are not always independent. Devices like chargers short the data lines together as a way of signaling to the host computer.
Ironically I just broke a USB-A to USB-C cable. It was attached from wall receptacle to my phone. I got up thinking my phone was unattached and yanked out of my phone and the receptacle and the cable no longer works.
I don’t know if it proves anyone’s point but it is topical.