this post was submitted on 31 Aug 2023
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I don't know much about cables so if type something wrong forgive me ...

I was wondering around with some old stuff, and found this cable that is usb to usb "as shown in the image below"

https://m.media-amazon.com/images/I/71hHpyqvvnS._AC_UF1000,1000_QL80_FMwebp_.jpg

Now what i thought was that it might be used to connect 2 computers with each other so i tried that and connected 2 computers with each other using it and nothing happened Can anyone tell me what this cable is even used for ???

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[–] [email protected] 21 points 1 year ago (1 children)

It's not an officially sanctioned application of USB, but some product vendors use it for various reasons. After all, a USB cable is just a bunch of wires (some twisted together a special way).

One example that springs to mind is the HTC Vive link box. This was made before USBC was very popular, and I'm guessing they wanted USB 3 speeds with a lower profile connector. Typically, you'd use an A to B cable, but the B connector is much taller.

[–] [email protected] 1 points 1 year ago (4 children)

Thanks for the info, I have another question. Can it be used to connect one pc to another maybe for sharing files or for doing some other stuff ?

[–] ArbitraryValue 10 points 1 year ago (1 children)

Generally no - USB connections are asymmetric, with hosts and devices. Your PCs are both hosts - they cannot function as devices or communicate with other hosts.

[–] [email protected] 4 points 1 year ago

Nope. Computer USB A ports are "upstream ports." Both computers would be expecting to find a downstream device on the port. USB needs a single host to control everything. Can't have two hosts.

[–] [email protected] 2 points 1 year ago (1 children)

If it was already tried with this specific cable and it didn't work, then this cable doesn't have the capability built in. Some cables like this have a bridge in the cable that allows pc to pc communication.

[–] [email protected] 3 points 1 year ago

Laplink is a major product that still does this. In the center is a controller that acts as a device to both ends, letting both PCs act as a host.

It still requires their software to make use of this connection, though.

[–] [email protected] 1 points 1 year ago

Not without special support from the hardware and software. But a smartphone is pretty much a PC with specialized hardware and software. And you can certainly plug your smartphone into a PC to share photo's.

[–] [email protected] 4 points 1 year ago

I had a cable like this, it was for an ancient Medion digital camera. No idea why they went with the full size USB female socket on the device, but it was just a simple USB cable that had male plugs on each end. Maybe it was cheaper, maybe it had debug purposes... we will never know.

I also tried to connect two PCs with it, it was my very first thought when I saw that cable. Obviously, it didn't work, nothing happened. Remember Total Commander had a "Connect two computers with USB" feature, was thinking maybe that will work with it, but nope... for that, a specialized USB cable/device was needed, not the one I had for the camera.

[–] [email protected] 4 points 1 year ago

I use it for connecting a computer to a KVM

[–] [email protected] 4 points 1 year ago

I've used these while developing consumer electronics. One product had only a single USB port, and it acted in device mode during bootup for debugging purposes before switching to host mode so it could talk to peripheral devices.

[–] [email protected] 3 points 1 year ago

It was used to power the Vive Wireless Adapter. I've also seen a Steelseries keyboard which used this cable type.

It's not widely used, but it's nice to be able to buy one

[–] [email protected] 2 points 1 year ago (1 children)

Image isn't working for me. Is it male-male? A lot of perepherals used to use those. If it's female-male it's just an extension.

[–] [email protected] 2 points 1 year ago

Yes, its male-male

[–] [email protected] 2 points 1 year ago

I have some converters that are female A to male B/micro/mini for instance. This would be useful as an extension in that case.

[–] [email protected] 2 points 1 year ago (1 children)

Connect 2 computers together to do what, exactly? The most common answers (e.g. sharing files) are all network-based. This cable definitely does not create a network connection

[–] [email protected] 1 points 1 year ago (1 children)

The USB protocol can indeed handle file transfers, not sure why windows by default wouldn't have support. But when you plug in a phone or hard drive/thumb drive by USB the first thing it asks is if you want to transfer files.

There is absolutely no reason why you wouldn't also want to file transfer between two computers, or say a laptop and a desktop. Just isn't supported by default, but there is software that can give you that feature.

Edit: it looks like in order to get windows to do a USB file transfer by default, the cable itself needs to have an identifying chip. So that windows doesn't use one of the default protocols and try to transfer power as well. I guess there's just no support for computers to identify themselves, it's assumed they will always be the host device and just passively wait for the device on the other end to identify itself. So the software just adds the ability to set one computer as a USB client and identify itself.

[–] [email protected] 1 points 1 year ago

There are many, many ways to transfer files. Many phones present themselves as a Mass Storage device (i.e. same as a thumb drive). Others use the Media Transfer Protocol. In any case, your device end has to be configured as such, which cannot be done from a Windows host. USB on the Go (and by extension, USB-C) offers some very limited abilities for something to switch between host and device (master/slave), but it's up to each device to enable that functionality.

When most of us share files on a PC, we are using SMB. This is what Windows typically means by sharing files, and is network-based.

Regardless, you always have to configure each side on what/how to share, and how to access that share. Most phones have a default configuration for this (and it's not everything on your phone), and Windows makes this type of access easy and direct. Again, there are other options, such as the Android Debug Bridge, which are much more complicated.

(As for the identifying chip, there are chips that present themselves in different ways on demand. It is a massive security risk, and has been exploited in the past. Examples are fake keyboards, fake network adapters, and even fake storage - although that's usually technically real, and used to deliver a malicious payload)

[–] scottmeme 1 points 1 year ago (2 children)

That's how you kill a USB port 101

[–] ArbitraryValue 4 points 1 year ago* (last edited 1 year ago) (1 children)

Why would it kill the port? I think the power lines would be at equal voltages on both ends and the data lines just wouldn't do anything.

[–] [email protected] 0 points 1 year ago (1 children)

Not exactly equal. One will try to feed to another which can kill it. It's not made to be connected like this. Maybe they could even fight if it tries to compensate by increasing voltage.

But hopefully there's some protection that disables the USB port before something ugly happens.

[–] [email protected] 3 points 1 year ago

This is entirely dependent on how the circuitry is set up. However USB voltage is always 5 volts and the controller doesn‘t go over that.

[–] [email protected] 2 points 1 year ago

Do you mean that it was risky connecting one pc to another with this usb to usb cable ???

[–] [email protected] 1 points 1 year ago

I use a cable like that to link two Car dvd players that are in the back seat. One’s the player with the disc in it and the other is just a viewer, both hang from the front seat head-rests.

[–] [email protected] 1 points 1 year ago (1 children)

Well, I've seen this stupid USB cable before. I think it was external HDD on AliExpress.

[–] [email protected] 2 points 1 year ago

Yep, I have an external IDE/SATA reader that uses one of these cables.