Re:Apple Lightning
by jcrawfordor on Wednesday July 01, 2020 @07:03PM
(#23707872)
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.
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
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?
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.
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.
So we should buy expensive cables and cheap power supplies?
Re:Apple Lightning
by chrisrogers on Thursday July 02, 2020 @01:35AM
(#23710328)
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.
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.
There was already a huge installed base of cheap power supplies
The other end of the cable is generic USB and can often be a naked, logic-free 5V supply.
I’ve cut the ends off way too many USB cables just to expose those red and black wires.
And surprisingly many cables even have just those two wires inside of them and can't carry any data
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.
Cables with electronics in them are useful for protections like this, and to facilitate safe interoperability of multiple voltage and current sources and sinks like on USB Type-C. The question becomes, is the protocol implemented in a simple, open consumer friendly way or is it implemented with other nasty antifeatures.