10 ms·

> 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 c

> 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 Apple did with lightning. Then you implement auto crossover detection, (edit: Gah! you don't even have to do that just flip the flipping wires) which had been around for years and is dirt cheap, in the hub. It would have been like, six, more transistors in the hub IC. edit: I completely forgot that reversible USB 2.0 plugs already exist and use a simpler (and cheaper) method. They just tend not to be so reliable because of the thinner materials and the fact that they're not spec-compliant so they tend to be grey market jobs made for the lowest price possible. Here is one: https://www.amazon.com/Tripp-Lite-Universal-Reversible-UR050-003-RA/dp/B00ESZIIRU https://www.amazon.com/Tripp-Lite-Universal-Reversible-UR050... No doubling of wires or circuits required, just a thin double-sided PCB. Was the connector form-factor inherited from an earlier project and the players didn't want to design a new one?

gzalo 3y ago
> Then you implement auto crossover detection, dwhich had been around for years Mdi-x/auto crossover for ethernet was introduced in 1999, that is after USB (1996) was designed, not sure of the technique was known at that time
- dboreham 3y ago
  There were auto-crossover RS-232 boxes going back deep into the 1980s.
  - sitzkrieg 3y ago
    with baud rate detection to boot (down the line)
    - deleted 3y ago
      [deleted]
- userbinator 3y ago
  You can't do "auto crossover" with USB because it needs to distinguish between D+/D- for speed selection. https://electronics.stackexchange.com/questions/73295/in-a-usb-cable-is-it-ok-to-swap-the-d-and-d-wires https://electronics.stackexchange.com/questions/73295/in-a-u... It works for Ethernet because the transmit and receive lanes are separate, but with USB, there's only one pair used for both directions.
  - ilyt 3y ago
    It doesn't need to. It chose to. They could just use different way to do it. Like, I dunno, a single packet of negotiation in slow mode...
- crote 3y ago
  Not really relevant. Ethernet needs crossover because it has dedicated transmit/receive pairs, but USB 1.x/2.0 uses a single wire pair for both tx & rx. Ethernet crossover is pretty much identical to serial null modem cables, and those were around for a few decades by then. USB "crossover" of the single differential wire pair would be an inversion of 0 and 1. Pretty trivial to do once you figure out a way to communicate crossover or not.
whoooooo123 3y ago
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 design change.
- fennecfoxy 3y ago
  Tbf I think the most prevalent issue with USB was from people plugging them in where they cannot see the port properly, ie the back of a computer tower (most often) or back of TV/console etc. Not really sure that that's USB's fault so much as a lack of front USB ports. I think in those cases the consumer can chose to get some sort of hub that's easier to access/can be pulled out from behind their setup. Now that C exists though, idk if we really need to go much further. Connector much smaller than it is now will become fragile. I've always thought they could add a single fiber core to USB cables for some "ultra high speed" standard, since USB4 is predicted to top out at 80GBps, but we could get 50Tbps or so over a single fiber if we really needed to. But after owning several fiber cables, for networking and HDMI fiber based cables...yeah they're far, far too weak to replace copper. Just look at 'em wrong and they snap/break. Plus tbf if we get 80gbps from usb4...the problem then becomes that we don't reaaaally have a use case for that speed. Maybe network adaptors, but beyond that...I mean a modern SSD will saturate that with a sequential read I suppose, but still.
- davidgay 3y ago
  That only works when you can see the place you're connecting to, or have used it many times. I've definitely cursed many times failing to plug in non-rectangular VGA, serial and parallel cables ;) [edit: it is still better, but not a panacea]
- stevage 3y ago
  Even having a bump on the rubber moulding as part of the standard would have solved the problem.
userbinator 3y ago
There are also reversible USB plugs that are a single "tongue", inheriting that design from USB drives that don't have any plug to speak of but look more like a card-edge connector: https://www.pcgamer.com/youre-telling-me-we-could-have-had-reversible-usb-cables-all-along/ https://www.pcgamer.com/youre-telling-me-we-could-have-had-r... https://2b.com.eg/en/2b-cv177-cable-usb-type-a-reversible-plug-to-micro-5pin-1m-black.html https://2b.com.eg/en/2b-cv177-cable-usb-type-a-reversible-pl...
- Waterluvian 3y ago
  I got these by accident, spent a month thinking I had incredible USB skills, then discovered and became fascinated by the tongue.
  - mikercampbell 3y ago
    This is like in basketball where they throw it right next to the hoop for someone to make an innuendo slam dunk, right??
- musicale 3y ago
  PCgamer: > Incidentally, the late Steve Jobs deserves a tip-of-the-hat for helping USB become a long-lasting standard. It was in 1998 that USB made some real headway, courtesy of the iMac G3, the first computer to ship with only USB ports for external devices (there were no serial or parallel ports). That came three years after USB 1.0 debuted, with a data rate of 12Mbps. Also PCgamer: > Given that it was a protocol designed to counter the typically Apple expense of sticking Firewire onto a motherboard, cost was the biggest reason for the eventual success of USB as a thing Apple started building FireWire 400 into Macs when 12Mbps USB 1.0 was not really an equivalent. USB 2.0 didn't make the cut for the first generation iPod but was supported on subsequent models.
  - rusk 3y ago
    > the first computer to ship with only USB ports I remember presenting this in a project as an undergraduate and I was challenged by the lecturer that it would be highly unusual for a consumer device to ship without RS232 and I could only say “yeah”
dylan604 3y ago
>edit: Gah! you don't even have to do that just flip the flipping wires) Isn't that essentially what all ethernet cables do? it's not like this something never done before.
- JoblessWonder 3y ago
  When was Auto MDI-X introduced? A quick google failed to get me an answer but I remember USB being available while I still needed a crossover cable to hook up 2 switches.
  - Scoundreller 3y ago
    oh god, I was made to be an idiot when I once told someone they would need a crossover cable to do what they wanted to do a few years ago...
    - JoblessWonder 3y ago
      If it makes you feel any better... for some reason there are some currently in production business jets that still require crossover cables for maintenance... so they ARE still required sometimes.
      - Scoundreller 3y ago
        I've also dug further into my parts bin thinking "oh, that yellow cable would've been perfect, but I need a non-crossover cable"... could've used the yellow one instead of digging further. Ah well.
      - DANmode 3y ago
        Security through obscurity?
      - mmac_ 3y ago
        You encounter this in older industrial equipment. Some of the old ethernet chipsets don't support automatically switching the pairs around. It's not really a problem since at least in our local area they need to be installed by licensed cablers who are used to dealing with legacy devices. Many devices won't get updated until chipsets go EOL or there's some other compelling reason to do so. Having said that, modern chipsets seem to all support it.
kybernetikos 3y ago
Couldn't original USB have used TRRS? That's better than reversible - an infinite number of orientations are allowed.
- userbinator 3y ago
  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/as_a_reminder_while_the_usb_is_plugged_do_not/ https://www.reddit.com/r/ErgoMechKeyboards/comments/rt083u/a... http://www.totekinternational.com/35mm-trrs-to-usb-a-male-cable-adapter.html http://www.totekinternational.com/35mm-trrs-to-usb-a-male-ca... https://pinoutguide.com/PortableDevices/ipod_shuffle_pinout.shtml https://pinoutguide.com/PortableDevices/ipod_shuffle_pinout....
  - microtonal 3y ago
    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 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 that is on, rather than protect against doing this accidentally sometime. Given that, it probably made more sense to completely avoid the issue.
    - crote 3y ago
      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!
  - 3y ago
jbverschoor 3y ago
I think he DID explain why: he didn’t and doesn’t know how
ozymandias12 3y ago
[flagged]
randyrand 3y ago
To help visualize: 1: GND 2: DATA +/- 3: VCC 4: DATA +/- 5: GND
- userbinator 3y ago
  With that pinout you'd end up with one orientation being full/high-speed and the other being low speed. Edit: see https://en.wikipedia.org/wiki/USB_communications#Signaling_state https://en.wikipedia.org/wiki/USB_communications#Signaling_s...
  - moring 3y ago
    Only if you don't also redefine the convention to select speeds.
  - anticensor 3y ago
    Would be an acceptable tradeoff.
  - kelnos 3y ago
    But when the plug was designed, there was only one speed.
- levidos 3y ago
  Can't that square metal be used as ground?
  - klysm 3y ago
    You don’t always want the shield coupled to the signal ground. If it’s coupled on both sides then you can have all kinds of fun problems. Ideally, the shield should be connected to the ground on one end
    - effie 3y ago
      > Question: “I have been told that you should only ground the Ethernet cable at one end. Is this true?” > > Answer: “Sometimes yes, but only if you are seeking to avoid a ground loop. You likely don’t have to worry about this. If you are running shielded Ethernet between two structures that have their own separate AC systems or separate grounding rods installed, then YES, you should worry about what is known as a ground loop. A ground loop occurs when you have actual conflicting AC ground systems. Merely bonding your Ethernet cable at multiple points to the same AC grounding system in a single structure does not create ground loops. Think in terms of ground rods. How many ground rods are involved? If you have more than one with more than one structure involved then you are wise to bond to ground at a single end only.” From https://www.truecable.com/blogs/cable-academy/residential-bonding-and-grounding-of-shielded-ethernet-cable-systems#page_comments=1 https://www.truecable.com/blogs/cable-academy/residential-bo...
kelnos 3y ago
Ugh, when I read that line I immediately came here to comment, but you beat me to it. I really really really hope that this was just an error by the journalist, and not Bhatt essentially lying to justify the choice.
dheera 3y ago
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.
- crote 3y ago
  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.
  - deleted 3y ago
    [deleted]
- ilyt 3y ago
  Maybe if you have no clue about electronics don't talk about electronics... > Or do like Comcast does and put all bidirectional data through 1 conductor at multi-gigabit speeds. And how much modem's transceiver cost ? And how does that compare to cost of computer mouse or other cheap USB peripherals.
  - dheera 3y ago
    They'll cost 1/100 the price if every USB port in the world uses them. Auto parts for common models of cars are so incredibly cheap for a reason.
    - ilyt 3y ago
      USB1 was designed in times where transistors were significantly more expensive. And in times where laptops or phones or any other situation when you disconnected peripherals were far less common. Like, it still was improvement over PS/2. It's also not just few transistors to flip the lines around, it's also the logic to drive that
crote 3y ago
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.
ilyt 3y ago
You have to consider that initially it was supposed to be connector for stuff like mouses or keyboards or gamepads or printers. 12Mbits. But yeah that was only one of many misdesigns along the way. Like making turning ports on and off optional features, mini-usb (seriously, none other usb version I've seen failed as often as mini-usb connectors), just how overcomplicated USB-PD is, or the recent mess in USB-C cabling.

gzalo 3y ago

> Then you implement auto crossover detection, dwhich had been around for years Mdi-x/auto crossover for ethernet was introduced in 1999, that is after USB (1996) was designed, not sure of the technique was known at that time

dboreham 3y ago
There were auto-crossover RS-232 boxes going back deep into the 1980s.
- sitzkrieg 3y ago
  with baud rate detection to boot (down the line)
  - deleted 3y ago
    [deleted]
userbinator 3y ago
You can't do "auto crossover" with USB because it needs to distinguish between D+/D- for speed selection. https://electronics.stackexchange.com/questions/73295/in-a-usb-cable-is-it-ok-to-swap-the-d-and-d-wires https://electronics.stackexchange.com/questions/73295/in-a-u... It works for Ethernet because the transmit and receive lanes are separate, but with USB, there's only one pair used for both directions.
- ilyt 3y ago
  It doesn't need to. It chose to. They could just use different way to do it. Like, I dunno, a single packet of negotiation in slow mode...
crote 3y ago
Not really relevant. Ethernet needs crossover because it has dedicated transmit/receive pairs, but USB 1.x/2.0 uses a single wire pair for both tx & rx. Ethernet crossover is pretty much identical to serial null modem cables, and those were around for a few decades by then. USB "crossover" of the single differential wire pair would be an inversion of 0 and 1. Pretty trivial to do once you figure out a way to communicate crossover or not.

whoooooo123 3y ago

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 design change.

fennecfoxy 3y ago
Tbf I think the most prevalent issue with USB was from people plugging them in where they cannot see the port properly, ie the back of a computer tower (most often) or back of TV/console etc. Not really sure that that's USB's fault so much as a lack of front USB ports. I think in those cases the consumer can chose to get some sort of hub that's easier to access/can be pulled out from behind their setup. Now that C exists though, idk if we really need to go much further. Connector much smaller than it is now will become fragile. I've always thought they could add a single fiber core to USB cables for some "ultra high speed" standard, since USB4 is predicted to top out at 80GBps, but we could get 50Tbps or so over a single fiber if we really needed to. But after owning several fiber cables, for networking and HDMI fiber based cables...yeah they're far, far too weak to replace copper. Just look at 'em wrong and they snap/break. Plus tbf if we get 80gbps from usb4...the problem then becomes that we don't reaaaally have a use case for that speed. Maybe network adaptors, but beyond that...I mean a modern SSD will saturate that with a sequential read I suppose, but still.
davidgay 3y ago
That only works when you can see the place you're connecting to, or have used it many times. I've definitely cursed many times failing to plug in non-rectangular VGA, serial and parallel cables ;) [edit: it is still better, but not a panacea]
stevage 3y ago
Even having a bump on the rubber moulding as part of the standard would have solved the problem.

userbinator 3y ago

There are also reversible USB plugs that are a single "tongue", inheriting that design from USB drives that don't have any plug to speak of but look more like a card-edge connector: https://www.pcgamer.com/youre-telling-me-we-could-have-had-reversible-usb-cables-all-along/ https://www.pcgamer.com/youre-telling-me-we-could-have-had-r... https://2b.com.eg/en/2b-cv177-cable-usb-type-a-reversible-plug-to-micro-5pin-1m-black.html https://2b.com.eg/en/2b-cv177-cable-usb-type-a-reversible-pl...

Waterluvian 3y ago
I got these by accident, spent a month thinking I had incredible USB skills, then discovered and became fascinated by the tongue.
- mikercampbell 3y ago
  This is like in basketball where they throw it right next to the hoop for someone to make an innuendo slam dunk, right??
musicale 3y ago
PCgamer: > Incidentally, the late Steve Jobs deserves a tip-of-the-hat for helping USB become a long-lasting standard. It was in 1998 that USB made some real headway, courtesy of the iMac G3, the first computer to ship with only USB ports for external devices (there were no serial or parallel ports). That came three years after USB 1.0 debuted, with a data rate of 12Mbps. Also PCgamer: > Given that it was a protocol designed to counter the typically Apple expense of sticking Firewire onto a motherboard, cost was the biggest reason for the eventual success of USB as a thing Apple started building FireWire 400 into Macs when 12Mbps USB 1.0 was not really an equivalent. USB 2.0 didn't make the cut for the first generation iPod but was supported on subsequent models.
- rusk 3y ago
  > the first computer to ship with only USB ports I remember presenting this in a project as an undergraduate and I was challenged by the lecturer that it would be highly unusual for a consumer device to ship without RS232 and I could only say “yeah”

dylan604 3y ago

>edit: Gah! you don't even have to do that just flip the flipping wires) Isn't that essentially what all ethernet cables do? it's not like this something never done before.

JoblessWonder 3y ago
When was Auto MDI-X introduced? A quick google failed to get me an answer but I remember USB being available while I still needed a crossover cable to hook up 2 switches.
- Scoundreller 3y ago
  oh god, I was made to be an idiot when I once told someone they would need a crossover cable to do what they wanted to do a few years ago...
  - JoblessWonder 3y ago
    If it makes you feel any better... for some reason there are some currently in production business jets that still require crossover cables for maintenance... so they ARE still required sometimes.
    - Scoundreller 3y ago
      I've also dug further into my parts bin thinking "oh, that yellow cable would've been perfect, but I need a non-crossover cable"... could've used the yellow one instead of digging further. Ah well.
    - DANmode 3y ago
      Security through obscurity?
    - mmac_ 3y ago
      You encounter this in older industrial equipment. Some of the old ethernet chipsets don't support automatically switching the pairs around. It's not really a problem since at least in our local area they need to be installed by licensed cablers who are used to dealing with legacy devices. Many devices won't get updated until chipsets go EOL or there's some other compelling reason to do so. Having said that, modern chipsets seem to all support it.

kybernetikos 3y ago

Couldn't original USB have used TRRS? That's better than reversible - an infinite number of orientations are allowed.

userbinator 3y ago
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/as_a_reminder_while_the_usb_is_plugged_do_not/ https://www.reddit.com/r/ErgoMechKeyboards/comments/rt083u/a... http://www.totekinternational.com/35mm-trrs-to-usb-a-male-cable-adapter.html http://www.totekinternational.com/35mm-trrs-to-usb-a-male-ca... https://pinoutguide.com/PortableDevices/ipod_shuffle_pinout.shtml https://pinoutguide.com/PortableDevices/ipod_shuffle_pinout....
- microtonal 3y ago
  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 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 that is on, rather than protect against doing this accidentally sometime. Given that, it probably made more sense to completely avoid the issue.
  - crote 3y ago
    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!
- 3y ago

jbverschoor 3y ago

I think he DID explain why: he didn’t and doesn’t know how

ozymandias12 3y ago

[flagged]

randyrand 3y ago

To help visualize: 1: GND 2: DATA +/- 3: VCC 4: DATA +/- 5: GND

userbinator 3y ago
With that pinout you'd end up with one orientation being full/high-speed and the other being low speed. Edit: see https://en.wikipedia.org/wiki/USB_communications#Signaling_state https://en.wikipedia.org/wiki/USB_communications#Signaling_s...
- moring 3y ago
  Only if you don't also redefine the convention to select speeds.
- anticensor 3y ago
  Would be an acceptable tradeoff.
- kelnos 3y ago
  But when the plug was designed, there was only one speed.
levidos 3y ago
Can't that square metal be used as ground?
- klysm 3y ago
  You don’t always want the shield coupled to the signal ground. If it’s coupled on both sides then you can have all kinds of fun problems. Ideally, the shield should be connected to the ground on one end
  - effie 3y ago
    > Question: “I have been told that you should only ground the Ethernet cable at one end. Is this true?” > > Answer: “Sometimes yes, but only if you are seeking to avoid a ground loop. You likely don’t have to worry about this. If you are running shielded Ethernet between two structures that have their own separate AC systems or separate grounding rods installed, then YES, you should worry about what is known as a ground loop. A ground loop occurs when you have actual conflicting AC ground systems. Merely bonding your Ethernet cable at multiple points to the same AC grounding system in a single structure does not create ground loops. Think in terms of ground rods. How many ground rods are involved? If you have more than one with more than one structure involved then you are wise to bond to ground at a single end only.” From https://www.truecable.com/blogs/cable-academy/residential-bonding-and-grounding-of-shielded-ethernet-cable-systems#page_comments=1 https://www.truecable.com/blogs/cable-academy/residential-bo...

kelnos 3y ago

Ugh, when I read that line I immediately came here to comment, but you beat me to it. I really really really hope that this was just an error by the journalist, and not Bhatt essentially lying to justify the choice.

dheera 3y ago

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.

crote 3y ago
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.
- deleted 3y ago
  [deleted]
ilyt 3y ago
Maybe if you have no clue about electronics don't talk about electronics... > Or do like Comcast does and put all bidirectional data through 1 conductor at multi-gigabit speeds. And how much modem's transceiver cost ? And how does that compare to cost of computer mouse or other cheap USB peripherals.
- dheera 3y ago
  They'll cost 1/100 the price if every USB port in the world uses them. Auto parts for common models of cars are so incredibly cheap for a reason.
  - ilyt 3y ago
    USB1 was designed in times where transistors were significantly more expensive. And in times where laptops or phones or any other situation when you disconnected peripherals were far less common. Like, it still was improvement over PS/2. It's also not just few transistors to flip the lines around, it's also the logic to drive that

crote 3y ago

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.

ilyt 3y ago

You have to consider that initially it was supposed to be connector for stuff like mouses or keyboards or gamepads or printers. 12Mbits. But yeah that was only one of many misdesigns along the way. Like making turning ports on and off optional features, mini-usb (seriously, none other usb version I've seen failed as often as mini-usb connectors), just how overcomplicated USB-PD is, or the recent mess in USB-C cabling.