4 ms·

This means there’s a small microcontroller inside the cable with information on the cable’s capabilities. More evidence that USB-C is an insanely overengineere

This means there’s a small microcontroller inside the cable with information on the cable’s capabilities. More evidence that USB-C is an insanely overengineered spec. Cables should be dumb pipes, not devices with their own active circuitry. IMHO Ethernet, while not perfect, got this part right. The only reason the signals don’t exactly match the one above is just the orientation of the cable. This is one of the more perplexing design decisions. Was simply mirroring the contacts too simple for them? Did someone imagine a use-case where they wanted to detect the orientation of the cable? WTF.

paholg 1y ago
Ethernet doesn't support 240 W. I am very happy that I can charge my phone and laptop from the same charger, and don't ever have to worry about whether the cable I'm using will be a fire hazard.
- deleted 1y ago
  [deleted]
- userbinator 1y ago
  PoE has been around for longer, and while it doesn't go that high (90W --- but at much longer distances), it uses passive cables just fine.
  - fooblaster 1y ago
    POE is an quite expensive thing to implement on a board. Flyback transformers are essentially required to support the standard.
  - lxgr 1y ago
    At the cost of much higher complexity on each end. USB-C still supports completely passive old chargers and devices.
- chongli 1y ago
  The cable can still be a fire hazard if it’s a cheap cable that lies about its rated wattage, no?
  - rokkamokka 1y ago
    That goes for anything that lies about its rating though
    - chongli 1y ago
      Right but consumers are much more likely to buy a cheap USB charge cable that lies about its rating (via internal chip) than an Ethernet cable that lies about its rating on the package.
      - NetMageSCW 1y ago
        It doesn’t seem to be a huge problem with extension cords.
  - dotancohen 1y ago
    Do ethernet cables even specify a wattage?
deleted 1y ago
[deleted]
lxgr 1y ago
So how’d you safely solve having cables of (widely) varying resistance? I appreciate having the option to choose between a thin cable for charging only, and a pretty thick (and also heavy, inflexible, and relatively expensive) one for high-speed data transfer and charging. The only alternative to that would seem to be having different ports per device, which is infeasible in many cases, and inflexible in most others. > Was simply mirroring the contacts too simple for them? That would require twice the number of contacts for the same number of physical wires, which would make the plugs even larger.
- userbinator 1y ago
  So how’d you safely solve having cables of (widely) varying resistance? Smartphones already do this. They essentially measure the resistance of the cable by measuring the voltage and correlating it with the current drawn, and regulate the current accordingly. That would require twice the number of contacts for the same number of physical wires, which would make the plugs even larger. No. Look at the pinout. It's not symmetrical. They could've made it perfectly symmetrical.
  - dvdkon 1y ago
    That's not true, see this random pinout diagram: https://acroname.com/sites/default/files/shared/alt_mode_-_displayport_pinout.png https://acroname.com/sites/default/files/shared/alt_mode_-_d...
  - lxgr 1y ago
    > It's not symmetrical. They could've made it perfectly symmetrical. Without internally connecting all corresponding pins to the same wire? To what benefit? The parts that need to be symmetric for passive legacy devices already are.
  - amluto 1y ago
    > Smartphones already do this. They essentially measure the resistance of the cable by measuring the voltage and correlating it with the current drawn, and regulate the current accordingly. Not sufficient. It’s easy to have a cable where the long conductors can safely carry a lot more current than the terminations. Or one could have a 1 foot thin cable connected in series with a 10 foot thick cable. For that matter, a short low-ampacity cable would look just like a long high-ampacity cable.
duskwuff 1y ago
> Cables should be dumb pipes, not devices with their own active circuitry. You only need the active circuitry for high-power (240W) or high-speed (Thunderbolt) cables. Ordinary cables just need a single, cheap resistor.
- lxgr 1y ago
  C-to-C cables never have a resistor for identification; those are for devices or legacy cables/adapters to USB-A/B. “Active” is also somewhat ambiguous: E-marked cables can be both passive or active in terms of what they do with the signal on the high speed data lines (such as amplifying it, converting it to optical etc.)
Tharre 1y ago
> More evidence that USB-C is an insanely overengineered spec. Cables should be dumb pipes, not devices with their own active circuitry. Why, to what end? They don't add any noticeable amount of cost to the cables and it's a whole lot better of a solution for consumers then requiring all cables to carry 5 amps and thus making them thicker. > Did someone imagine a use-case where they wanted to detect the orientation of the cable? They didn't imagine anything, USB3.0 5Gpbs with only 2 differential pairs, like you'd have in a usb-c to usb-a cable, requires this. And you can't just connect them together like you'd do for USB2, the resulting stubs degrade the signal too much.
ironhaven 1y ago
The reason for detecting the orientation of the connector is for higher speed communication. USB-C 20gbps uses both sets of pins on the connector to shotgun two usb3.2 10gbps to get 20gbps. That is why the technical spec name for 20gbps is "USB 3.2 gen 2x2". That is what the "x2" means. Knowing that USB has this feature is follows that USB-C needs to be self orienting in case both ends of the connector plugged in different orientations. You say Ethernet got this part right, well it got this part right by not having a reversible connector. Ethernet has 4 tx/rx pair and USB-C has 2 rx/tx pairs per usb 3 connection with 4 in total for 20gbps. The difference is reversibility. Is it worth the tradeoff?
- userbinator 1y ago
  Most if not all Ethernet NICs have auto crossover and polarity detection. Some tolerate arbitrary lane swaps too.
  - lxgr 1y ago
    That might work for Ethernet, but how would you do that for any unidirectional USB-C alternate mode without protocol-level feedback such as analog audio or DisplayPort video? If you want to allow all of - Reversible connectors - Passive (except for marking), and as such relatively cheap, adapters and cables - Not wasting 50% of all pins on a completely symmetric design connected together in the cable or socket there's no way around having an asymmetrical cable design that lets the host know which signal to output on which pins.
    - NetMageSCW 1y ago
      You do it like Lightning did with a chip that controls the pinout as well as reporting the use case.
      - lxgr 1y ago
        That’s basically how USB-C does it too (except that the chip isn’t strictly necessary; an identifying resistor does the job for legacy adapters and cables). USB-C was heavily inspired by Lightning.
deleted 1y ago
[deleted]

paholg 1y ago

Ethernet doesn't support 240 W. I am very happy that I can charge my phone and laptop from the same charger, and don't ever have to worry about whether the cable I'm using will be a fire hazard.

deleted 1y ago
[deleted]
userbinator 1y ago
PoE has been around for longer, and while it doesn't go that high (90W --- but at much longer distances), it uses passive cables just fine.
- fooblaster 1y ago
  POE is an quite expensive thing to implement on a board. Flyback transformers are essentially required to support the standard.
- lxgr 1y ago
  At the cost of much higher complexity on each end. USB-C still supports completely passive old chargers and devices.
chongli 1y ago
The cable can still be a fire hazard if it’s a cheap cable that lies about its rated wattage, no?
- rokkamokka 1y ago
  That goes for anything that lies about its rating though
  - chongli 1y ago
    Right but consumers are much more likely to buy a cheap USB charge cable that lies about its rating (via internal chip) than an Ethernet cable that lies about its rating on the package.
    - NetMageSCW 1y ago
      It doesn’t seem to be a huge problem with extension cords.
- dotancohen 1y ago
  Do ethernet cables even specify a wattage?

deleted 1y ago

[deleted]

lxgr 1y ago

So how’d you safely solve having cables of (widely) varying resistance? I appreciate having the option to choose between a thin cable for charging only, and a pretty thick (and also heavy, inflexible, and relatively expensive) one for high-speed data transfer and charging. The only alternative to that would seem to be having different ports per device, which is infeasible in many cases, and inflexible in most others. > Was simply mirroring the contacts too simple for them? That would require twice the number of contacts for the same number of physical wires, which would make the plugs even larger.

userbinator 1y ago
So how’d you safely solve having cables of (widely) varying resistance? Smartphones already do this. They essentially measure the resistance of the cable by measuring the voltage and correlating it with the current drawn, and regulate the current accordingly. That would require twice the number of contacts for the same number of physical wires, which would make the plugs even larger. No. Look at the pinout. It's not symmetrical. They could've made it perfectly symmetrical.
- dvdkon 1y ago
  That's not true, see this random pinout diagram: https://acroname.com/sites/default/files/shared/alt_mode_-_displayport_pinout.png https://acroname.com/sites/default/files/shared/alt_mode_-_d...
- lxgr 1y ago
  > It's not symmetrical. They could've made it perfectly symmetrical. Without internally connecting all corresponding pins to the same wire? To what benefit? The parts that need to be symmetric for passive legacy devices already are.
- amluto 1y ago
  > Smartphones already do this. They essentially measure the resistance of the cable by measuring the voltage and correlating it with the current drawn, and regulate the current accordingly. Not sufficient. It’s easy to have a cable where the long conductors can safely carry a lot more current than the terminations. Or one could have a 1 foot thin cable connected in series with a 10 foot thick cable. For that matter, a short low-ampacity cable would look just like a long high-ampacity cable.

duskwuff 1y ago

> Cables should be dumb pipes, not devices with their own active circuitry. You only need the active circuitry for high-power (240W) or high-speed (Thunderbolt) cables. Ordinary cables just need a single, cheap resistor.

lxgr 1y ago
C-to-C cables never have a resistor for identification; those are for devices or legacy cables/adapters to USB-A/B. “Active” is also somewhat ambiguous: E-marked cables can be both passive or active in terms of what they do with the signal on the high speed data lines (such as amplifying it, converting it to optical etc.)

Tharre 1y ago

> More evidence that USB-C is an insanely overengineered spec. Cables should be dumb pipes, not devices with their own active circuitry. Why, to what end? They don't add any noticeable amount of cost to the cables and it's a whole lot better of a solution for consumers then requiring all cables to carry 5 amps and thus making them thicker. > Did someone imagine a use-case where they wanted to detect the orientation of the cable? They didn't imagine anything, USB3.0 5Gpbs with only 2 differential pairs, like you'd have in a usb-c to usb-a cable, requires this. And you can't just connect them together like you'd do for USB2, the resulting stubs degrade the signal too much.

ironhaven 1y ago

The reason for detecting the orientation of the connector is for higher speed communication. USB-C 20gbps uses both sets of pins on the connector to shotgun two usb3.2 10gbps to get 20gbps. That is why the technical spec name for 20gbps is "USB 3.2 gen 2x2". That is what the "x2" means. Knowing that USB has this feature is follows that USB-C needs to be self orienting in case both ends of the connector plugged in different orientations. You say Ethernet got this part right, well it got this part right by not having a reversible connector. Ethernet has 4 tx/rx pair and USB-C has 2 rx/tx pairs per usb 3 connection with 4 in total for 20gbps. The difference is reversibility. Is it worth the tradeoff?

userbinator 1y ago
Most if not all Ethernet NICs have auto crossover and polarity detection. Some tolerate arbitrary lane swaps too.
- lxgr 1y ago
  That might work for Ethernet, but how would you do that for any unidirectional USB-C alternate mode without protocol-level feedback such as analog audio or DisplayPort video? If you want to allow all of - Reversible connectors - Passive (except for marking), and as such relatively cheap, adapters and cables - Not wasting 50% of all pins on a completely symmetric design connected together in the cable or socket there's no way around having an asymmetrical cable design that lets the host know which signal to output on which pins.
  - NetMageSCW 1y ago
    You do it like Lightning did with a chip that controls the pinout as well as reporting the use case.
    - lxgr 1y ago
      That’s basically how USB-C does it too (except that the chip isn’t strictly necessary; an identifying resistor does the job for legacy adapters and cables). USB-C was heavily inspired by Lightning.

deleted 1y ago

[deleted]