this post was submitted on 10 Oct 2023
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I found it at the dollar store.

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[–] [email protected] 9 points 1 year ago (6 children)

USB-A to USB-A cables do not exist, the USB standard does not allow them, if you have a cable with two USB-A connectors then it’s not actually a certified USB cable. The same goes for USB extension cables and this adapter. Note how there isn’t a ‘USB certified’ logo on the package.

[–] [email protected] 15 points 1 year ago* (last edited 1 year ago)

The cables exist; they just don't follow the standard. I've used them when developing consumer electronics: the host controller on the device switches to device mode in the bootloader, allowing a host machine to connect and debug/flash the device.

[–] [email protected] 14 points 1 year ago (2 children)

USB-A to USB-A cables do not exist

wtf are you talking about, of course they do.

[–] [email protected] 8 points 1 year ago* (last edited 1 year ago) (1 children)

They meant cables in spec with the USB specification at the time usb-a was new.

Now with usb-c, it's kinda moot, as most cables are male to male anyway.. of course that means we're more likely to see USB-C female to female adopters now

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

USB-C female to female adapters also are out of spec. The USB standard does not allow for extensions. USB cables only have male connectors (with the exception of USB-OTG dongles).

[–] [email protected] 0 points 1 year ago (2 children)

Show me where in the USB standards these are specified.

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

This is like saying that a building isn't a building if it's not up to code

[–] [email protected] 6 points 1 year ago (1 children)

Or like saying usb-a to usb-c adapters don't exist because they're not part of the standard but we all have like six of those damn things even though we've never actually bought a single one.

[–] [email protected] 3 points 1 year ago (1 children)

But those are actually part of the standard.

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

Are they? Everything I can find seems to say they aren't.

I remember when the first usb-c Macbooks hit stores Apple didn't have usb-a to c adapters for sale because they weren't in spec, a lot of reviews mentioned that.

[–] [email protected] 3 points 1 year ago* (last edited 1 year ago)

You can find compliance requirements in the document linked here: https://www.usb.org/document-library/usb-type-c-connectors-and-cable-assemblies-compliance-document

You want to look at table 3-6 for requirements for USB-C to legacy USB adapters.

[–] [email protected] 14 points 1 year ago (1 children)

They cables and exist and they work. So being "specified" doesn't mean jack shit.

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

They might sometimes work. They aren’t guaranteed to work.

[–] [email protected] 3 points 1 year ago (1 children)

USB-A to USB-A cables do exist.

I have seen many (very cheap) peripherals use USB-A sockets. I figure those sockets must be a few cents cheaper than alternatives.

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

And there was a USB certified logo on these cables and devices?

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

China stuff loves to slap logos on there that do not apply, so probably without having seen this particular abomination myself. Fake CE markings are super common though.

[–] [email protected] 3 points 1 year ago* (last edited 1 year ago) (1 children)

USB-A to USB-A doesn't exist

*looks at old charger from an American device*

HOLY SHIT A CRYPTID CALL SCP

[–] [email protected] 0 points 1 year ago (1 children)
[–] [email protected] 2 points 1 year ago* (last edited 1 year ago)

HOLY SHIT AN UNIDENTIFIED CRYPTID. CALL SCOOBYDOO!

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

They do exist, despite the USB standards not allowing them

See: cheapo video capture card for work, other side is just HDMI-IN and OUT

They shouldn't exist but don't mean they don't when you get the cheapest little devices you can find

[–] [email protected] -3 points 1 year ago* (last edited 1 year ago)

They do exist, despite the USB standards not allowing them

A USB cable is a cable that conforms to the USB specification. If a cable does not conform to the USB specification then it isn’t an USB cable by definition

I’m not saying a cable with 2 USB-A style connectors doesn’t exist, I’m just saying that it is not a USB cable. Just like a glass of Pepsi is not a glass of Coca-Cola even though it may look like one.

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

It’s not hard to imagine a product that would require one, though. It’s how every phone charging cable works, just with a different size male USB on one end.

[–] [email protected] 0 points 1 year ago* (last edited 1 year ago)

It’s how every phone charging cable works, just with a different size male USB on one end.

No, it's exactly not how every phone charging cable works, at least not for non USB-C cables.

Pre-USB-C cables are explicitly unidirectional. In USB there are 'hosts' (usually computers) and 'devices' (flashdrives, camera's, mice, keyboards, etc.). The host side always has a female USB-A connector, a device either has a female USB-B connector (if it's intended to be used with a cable), or a male USB-A (if it's intended to be plugged in directly into a host, like a flash drive). A real, standard-conformant USB cable can only go from USB-A male to USB-B male (with the addition of USB-C, it can also go from A-to-C, from C-to-B, or C-to-C). Never A-to-A or B-to-B, extension cables (male to female) of any type, A, B or C, are not allowed either.

USB was specifically designed like this so you can never connect a device to a device or a host to a host.

On the host side, you pretty much only see full size USB-A ports. On the device side there are 3 common types of USB-B ports: standard size (you can for example see these on printers and scanners), mini-USB-B used a lot on older phones, and later micro-USB-B. On each side the male part is on the cable, the female part is on the host or device.