5 ms·

Couldn't all of the protections on current delivery be implemented in the interface on the other end of the cable, though? This is the approach taken by basical

Couldn't all of the protections on current delivery be implemented in the interface on the other end of the cable, though? This is the approach taken by basically every other standard for negotiated power delivery. Even things like 802.3af which manage to deliver 48v at nearly an amp and with the complicating case of many valid devices not really tolerating any current delivered.

sjwright 6y ago
The other end of the cable is generic USB and can often be a naked, logic-free 5V supply.
- bigyikes 6y ago
  I’ve cut the ends off way too many USB cables just to expose those red and black wires.
  - epse 6y ago
    And surprisingly many cables even have just those two wires inside of them and can't carry any data
varenc 6y ago
The other end being USB-A power adapters? There’s a vast number of those of varying quality. Some have zero logic and just output 5V/1A. No way they could be trusted for this purpose. call this a “safety in depth” approach
- jayd16 6y ago
  So we should buy expensive cables and cheap power supplies?
  - gok 6y ago
    There was already a huge installed base of cheap power supplies
  - chrisrogers 6y ago
    Those cheap power supplies are ubiquitous, so it's more about Apple building their cables to exist in the built environment than dealing with the fallout of consumers busting up their expensive phones by charging them on whatever's lying around. Guarantee there was a consumer study where they compared reactions between these scenario.
  - varenc 6y ago
    The manufacturers knows that if it’s their product in contact when a user is shocked, they will get some blame even if it’s “really” the sketchy power supply’s fault. And since some cables have these safety features already, anyone making cables without them will appear extra negligent when bad things happen. The world is unfortunately not very efficient.
- chongli 6y ago
  No I think the GP meant the port on the iPhone as the “other end”. In other words, why not have all of the protection logic built into the phone?
  - projektfu 6y ago
    If the cable is dumb, it can’t switch the +5v power coming from a USB supply. If it can switch it, it’s not dumb.
  - rtpg 6y ago
    just as an example, imagine you end up putting a fuse in the cable. If the fuse blows, then the cable can be easily replaced. A chip in the iPhone.... not so much. Though likely there's something in the phone _as well_ as the cable.
WGH_ 6y ago
Isn't direct current component ignored by default just because Ethernet devices are galvanically isolated? I thought even if you applied some DC voltage to Ethernet without proper PoE negotation, nothing would happen at all.

sjwright 6y ago

The other end of the cable is generic USB and can often be a naked, logic-free 5V supply.

bigyikes 6y ago
I’ve cut the ends off way too many USB cables just to expose those red and black wires.
- epse 6y ago
  And surprisingly many cables even have just those two wires inside of them and can't carry any data

varenc 6y ago

The other end being USB-A power adapters? There’s a vast number of those of varying quality. Some have zero logic and just output 5V/1A. No way they could be trusted for this purpose. call this a “safety in depth” approach

jayd16 6y ago
So we should buy expensive cables and cheap power supplies?
- gok 6y ago
  There was already a huge installed base of cheap power supplies
- chrisrogers 6y ago
  Those cheap power supplies are ubiquitous, so it's more about Apple building their cables to exist in the built environment than dealing with the fallout of consumers busting up their expensive phones by charging them on whatever's lying around. Guarantee there was a consumer study where they compared reactions between these scenario.
- varenc 6y ago
  The manufacturers knows that if it’s their product in contact when a user is shocked, they will get some blame even if it’s “really” the sketchy power supply’s fault. And since some cables have these safety features already, anyone making cables without them will appear extra negligent when bad things happen. The world is unfortunately not very efficient.
chongli 6y ago
No I think the GP meant the port on the iPhone as the “other end”. In other words, why not have all of the protection logic built into the phone?
- projektfu 6y ago
  If the cable is dumb, it can’t switch the +5v power coming from a USB supply. If it can switch it, it’s not dumb.
- rtpg 6y ago
  just as an example, imagine you end up putting a fuse in the cable. If the fuse blows, then the cable can be easily replaced. A chip in the iPhone.... not so much. Though likely there's something in the phone _as well_ as the cable.

WGH_ 6y ago

Isn't direct current component ignored by default just because Ethernet devices are galvanically isolated? I thought even if you applied some DC voltage to Ethernet without proper PoE negotation, nothing would happen at all.