7 ms·

I lived through the pre-USB world, and things were even more "fun". In all seriousness though, the current state of a USB is ridiculous. My wife innocently as

I lived through the pre-USB world, and things were even more "fun". In all seriousness though, the current state of a USB is ridiculous. My wife innocently asked me why her USB C phone isn't triggering Android Auto in the car, and straight away you know it's because she bought a USB C power-only cable without knowing the difference. Nice.

bzb6 6y ago
Aren’t power-only cables a security feature?
- zdkl 6y ago
  They are, and frankly that they need to exist is the single most egregious example of why USB isn't what I need it to be. What (I'm surprised) I haven't seen is a male-to-female adapter with a switch on it that physically kills the data tx lines.
  - AussieWog93 6y ago
    A device very similar to the one you described exists: the aptly named "USB Condom"!
    - lasereyes136 6y ago
      Indeed, I have two of them. They don't always work correctly. Meaning they don't always charge depending on the device and cable you plug into them.
      - SAI_Peregrinus 6y ago
        I've got a (USB2) power monitor that includes a chip (just an STM8L051F3 microcontroller) to manage power negotiation and keep data disconnected. So it negotiates power with host and device separately, without ever needing to connect the data lines from host to device directly. I expect there are or will be versions for USB 3.<whatever I've lost track>.
        jasomill 6y ago
        For USB 2, widely-available battery packs compatible with whatever current negotiation standards your devices require work just as well, and have the added benefit of storing power. Less generally, these batteries can also break ground loops, which comes in handy when connecting a power supply to both a USB device and an attached analog audio device (e.g., iPhone and wired noise-canceling earbuds).
  - PeterisP 6y ago
    As far as I understand, that would make the cables near-unusable for actual charging as without the ability to negotiate power settings (over the data lines) they have to default to an extremely low charging rate. So instead of a physical switch it would have to be a smart device with logic that allows for the charging "handshake" but kills other data transfer.
    - R0b0t1 6y ago
      It's just a choice. A smart charger can detect if a battery is present, or at least some load that is safe to dump power into. You'll note that many chargers started dropping handshaking because it was inconvenient. To be compatible with anything you need it, but there's many that don't ask, though they may only work with the equipment they were sold with. (E.g. defaults to 5V 2A charging.)
      - michaelt 6y ago
        It's not a question of chargers: It's a question of laptops in standby. The historical design intent of USB is that, even when your laptop is in standby it still powers devices like your keyboard (so you can press keys to wake it up) and in exchange, devices promise to consume less than 2.5 milliamps (12.5 milliwatts) until they've negotiated permission to draw more from the host. After all, it'd suck if your laptop battery was going down noticeably even when the laptop was in standby. Of course, loads of vendors of cheap devices ignore this - the makers of a $5 rechargeable bike light or USB fan aren't going to put in the components needed to negotiate charging speed. But in principle if you made a USB cable with only the power pins connected, compliant devices should only charge exceptionally slowly, if at all. (Wall chargers, instead of enumerating as a USB host to negotiate power, used to put a certain value of resistor across the data lines, to signal what current the device could draw - this hasn't always been standardised, which is why phones and USB chargers can be incompatible)
        R0b0t1 6y ago
        Sounds like historical revisionism. Power limiting is possible without negotiation. It's easiest, for me, to find references to the safety aspect more than anything else. Note also a fair number of laptops (read: every one I have used and checked) use PS/2 internally because it is interrupt driven and even lower power than USB. There are also plenty of laptops that advertise high current phone charging while off, some of which do negotiation, some of which don't.
  - mFixman 6y ago
    Wouldn't it make more sense to control it by software? Android already allows you to only use an USB connection for charging. Setting this as the default when you are in an unknown place sounds reasonable.
    - Piskvorrr 6y ago
      It would be more convenient. Given that this is supposedly a security feature - no. Nope. Not at all: what is the state of the data line(s), and how do you know that it matches whatever indicator the cable uses? (There's no way to tell, and you don't - if software is involved, securing stuff becomes HARD, and proving security even harder.) OTOH, a USB Y-cable physically has no data lines connected on the extra USB-A male connector; it thus provides a far stronger guarantee that there is no data travelling across them. (Not foolproof, but safer than a software-controlled switch.)
      - mFixman 6y ago
        That's my point. If I can't tell whether this charging cable is secretly an USB keyboard, isn't it better to explicitly tell my cellphone to treat it as charge-only instead of relying on physical solutions?
        zdkl 6y ago
        My use case is I don't necessarily trust one end of the connection to behave, so I want the ability to just give/take power and involve exactly 0 software. I understand that's not the usual consumer story, and the best argument I can come up with for the general case is it could make any USB compatible wall plug safe to use to charge up.
        mFixman 6y ago
        I'm talking about using the phone's software to block the data connection. If you don't trust that cellphone won't transfer your private data via USB, I don't understand why you trust it not to do it via any wireless connection.
starfallg 6y ago
Our second car, a VW, comes with its own branded cables for this very purpose. My guess is that they got so many customers calling them about problems that it made sense for them to throw it in. They're pretty nice too, the only made in Germany USB-C/lightning cables I have ever used.
- the-dude 6y ago
  Does it actually say Made in Germany ? Otherwise, I would doubt it.
  - deleted 6y ago
    [deleted]
  - starfallg 6y ago
    Yes, it came in a sealed plastic bag with a label describing the contents and "Made in Germany" under it.
    - kozhevnikov 6y ago
      Based on eBay photos, it says "Distributed by Volkswagen Zubehör GmbH".
      - MichaelZuo 6y ago
        Well both can be true, though I would be surprised of the fact that there is an actual usb cable factory in germany.
        Piskvorrr 6y ago
        TBH, all that's required for this label is that the final product is assembled at a plant in Germany. So what usually happens is "bulk ship from anywhere, have a plant for packaging the individual items in Germany."
- moooo99 6y ago
danhor 6y ago
These aren't allowed by the usb standard, so it's a case of cheap manufacturers not respecting standards and messing things up.
- DrBazza 6y ago
  Possibly? A quick search of Amazon shows Anker, and others selling 'USB Powerline' cables, which is what we clearly had in the car.
  - zlsa 6y ago
    "Powerline" is an Anker name for their cables, and (to my knowledge) they all support at least USB 2.0.
- littlestymaar 6y ago
  Really? So people are supposed to plug their phones and laptop to public USB outlets with full USB cables? Given how many USB security vulns there are, I'm glad I can use a power-only cable when plugging to a third-party USB plug even if the USB standard think these cables should not exist…
  - lxgr 6y ago
    Power-only cables really are not a thing for USB-C. You need at least the configuration channel in order to negotiate charging voltage and maximum current. Maybe it's possible to make one lacking both USB 2 and 3 data though, but I haven't seen one yet. Nor have I seen a public USB-C outlet, for that matter, and I probably wouldn't be plugging my laptop or phone into one anyway: My own charger doesn't only protect me against bad intent, but also against cheap charging circuits that might or might not accidentally expose 220 Volt to my laptop's mainboard in case of faults.
    - littlestymaar 6y ago
      > Power-only cables really are not a thing for USB-C. You need at least the configuration channel in order to negotiate charging voltage and maximum current. Ouch. USB-C is even more fucked up than I thought… How does that even works with USB wall chargers? > Nor have I seen a public USB-C outlet, for that matter There are plenty of USB-A outlet everywhere (airport, trains, hotels, etc.), and most recent Android phones have only an USB-C port…
brigade 6y ago
Spec-compliant USB-C cables are still required to have the USB2 data lines hooked up, even "power-only" cables, and Android Auto / Carplay don't need beyond USB2

bzb6 6y ago

Aren’t power-only cables a security feature?

zdkl 6y ago
They are, and frankly that they need to exist is the single most egregious example of why USB isn't what I need it to be. What (I'm surprised) I haven't seen is a male-to-female adapter with a switch on it that physically kills the data tx lines.
- AussieWog93 6y ago
  A device very similar to the one you described exists: the aptly named "USB Condom"!
  - lasereyes136 6y ago
    Indeed, I have two of them. They don't always work correctly. Meaning they don't always charge depending on the device and cable you plug into them.
    - SAI_Peregrinus 6y ago
      I've got a (USB2) power monitor that includes a chip (just an STM8L051F3 microcontroller) to manage power negotiation and keep data disconnected. So it negotiates power with host and device separately, without ever needing to connect the data lines from host to device directly. I expect there are or will be versions for USB 3.<whatever I've lost track>.
      - jasomill 6y ago
        For USB 2, widely-available battery packs compatible with whatever current negotiation standards your devices require work just as well, and have the added benefit of storing power. Less generally, these batteries can also break ground loops, which comes in handy when connecting a power supply to both a USB device and an attached analog audio device (e.g., iPhone and wired noise-canceling earbuds).
- PeterisP 6y ago
  As far as I understand, that would make the cables near-unusable for actual charging as without the ability to negotiate power settings (over the data lines) they have to default to an extremely low charging rate. So instead of a physical switch it would have to be a smart device with logic that allows for the charging "handshake" but kills other data transfer.
  - R0b0t1 6y ago
    It's just a choice. A smart charger can detect if a battery is present, or at least some load that is safe to dump power into. You'll note that many chargers started dropping handshaking because it was inconvenient. To be compatible with anything you need it, but there's many that don't ask, though they may only work with the equipment they were sold with. (E.g. defaults to 5V 2A charging.)
    - michaelt 6y ago
      It's not a question of chargers: It's a question of laptops in standby. The historical design intent of USB is that, even when your laptop is in standby it still powers devices like your keyboard (so you can press keys to wake it up) and in exchange, devices promise to consume less than 2.5 milliamps (12.5 milliwatts) until they've negotiated permission to draw more from the host. After all, it'd suck if your laptop battery was going down noticeably even when the laptop was in standby. Of course, loads of vendors of cheap devices ignore this - the makers of a $5 rechargeable bike light or USB fan aren't going to put in the components needed to negotiate charging speed. But in principle if you made a USB cable with only the power pins connected, compliant devices should only charge exceptionally slowly, if at all. (Wall chargers, instead of enumerating as a USB host to negotiate power, used to put a certain value of resistor across the data lines, to signal what current the device could draw - this hasn't always been standardised, which is why phones and USB chargers can be incompatible)
      - R0b0t1 6y ago
        Sounds like historical revisionism. Power limiting is possible without negotiation. It's easiest, for me, to find references to the safety aspect more than anything else. Note also a fair number of laptops (read: every one I have used and checked) use PS/2 internally because it is interrupt driven and even lower power than USB. There are also plenty of laptops that advertise high current phone charging while off, some of which do negotiation, some of which don't.
- mFixman 6y ago
  Wouldn't it make more sense to control it by software? Android already allows you to only use an USB connection for charging. Setting this as the default when you are in an unknown place sounds reasonable.
  - Piskvorrr 6y ago
    It would be more convenient. Given that this is supposedly a security feature - no. Nope. Not at all: what is the state of the data line(s), and how do you know that it matches whatever indicator the cable uses? (There's no way to tell, and you don't - if software is involved, securing stuff becomes HARD, and proving security even harder.) OTOH, a USB Y-cable physically has no data lines connected on the extra USB-A male connector; it thus provides a far stronger guarantee that there is no data travelling across them. (Not foolproof, but safer than a software-controlled switch.)
    - mFixman 6y ago
      That's my point. If I can't tell whether this charging cable is secretly an USB keyboard, isn't it better to explicitly tell my cellphone to treat it as charge-only instead of relying on physical solutions?
      - zdkl 6y ago
        My use case is I don't necessarily trust one end of the connection to behave, so I want the ability to just give/take power and involve exactly 0 software. I understand that's not the usual consumer story, and the best argument I can come up with for the general case is it could make any USB compatible wall plug safe to use to charge up.
        mFixman 6y ago
        I'm talking about using the phone's software to block the data connection. If you don't trust that cellphone won't transfer your private data via USB, I don't understand why you trust it not to do it via any wireless connection.

starfallg 6y ago

Our second car, a VW, comes with its own branded cables for this very purpose. My guess is that they got so many customers calling them about problems that it made sense for them to throw it in. They're pretty nice too, the only made in Germany USB-C/lightning cables I have ever used.

the-dude 6y ago
Does it actually say Made in Germany ? Otherwise, I would doubt it.
- deleted 6y ago
  [deleted]
- starfallg 6y ago
  Yes, it came in a sealed plastic bag with a label describing the contents and "Made in Germany" under it.
  - kozhevnikov 6y ago
    Based on eBay photos, it says "Distributed by Volkswagen Zubehör GmbH".
    - MichaelZuo 6y ago
      Well both can be true, though I would be surprised of the fact that there is an actual usb cable factory in germany.
      - Piskvorrr 6y ago
        TBH, all that's required for this label is that the final product is assembled at a plant in Germany. So what usually happens is "bulk ship from anywhere, have a plant for packaging the individual items in Germany."
moooo99 6y ago

danhor 6y ago

These aren't allowed by the usb standard, so it's a case of cheap manufacturers not respecting standards and messing things up.

DrBazza 6y ago
Possibly? A quick search of Amazon shows Anker, and others selling 'USB Powerline' cables, which is what we clearly had in the car.
- zlsa 6y ago
  "Powerline" is an Anker name for their cables, and (to my knowledge) they all support at least USB 2.0.
littlestymaar 6y ago
Really? So people are supposed to plug their phones and laptop to public USB outlets with full USB cables? Given how many USB security vulns there are, I'm glad I can use a power-only cable when plugging to a third-party USB plug even if the USB standard think these cables should not exist…
- lxgr 6y ago
  Power-only cables really are not a thing for USB-C. You need at least the configuration channel in order to negotiate charging voltage and maximum current. Maybe it's possible to make one lacking both USB 2 and 3 data though, but I haven't seen one yet. Nor have I seen a public USB-C outlet, for that matter, and I probably wouldn't be plugging my laptop or phone into one anyway: My own charger doesn't only protect me against bad intent, but also against cheap charging circuits that might or might not accidentally expose 220 Volt to my laptop's mainboard in case of faults.
  - littlestymaar 6y ago
    > Power-only cables really are not a thing for USB-C. You need at least the configuration channel in order to negotiate charging voltage and maximum current. Ouch. USB-C is even more fucked up than I thought… How does that even works with USB wall chargers? > Nor have I seen a public USB-C outlet, for that matter There are plenty of USB-A outlet everywhere (airport, trains, hotels, etc.), and most recent Android phones have only an USB-C port…

brigade 6y ago

Spec-compliant USB-C cables are still required to have the USB2 data lines hooked up, even "power-only" cables, and Android Auto / Carplay don't need beyond USB2