On Sun, 21 Jun 2020 18:40:59 +0100
Chris Green  wrote:

>Dennis Lee Bieber  wrote:
>> On Sun, 21 Jun 2020 13:43:44 +0200, Deloptes  declaimed
>> the following:
>>
>> >
>> >OK, now I understand. It might depend on the cables, because as mentioned
>> >recent USB2 cables (mainly provided with phone chargers) are capable of
>> >caring the load (2A*5V=10W)
>> >
>>
>>         And do those cables also provide data transfer? I've had a few cell
>> phones that came with power-only USB-2 cables -- no data pins. {And
>> strangely, one of those would NOT charge using a common USB-2 charger [vs
>> phone dedicated charger] but WOULD charge when plugged into a laptop at
>> work... and I don't think the laptop had those special "charge mode" USB
>> ports)
>>
>Yes, if you look into it the USB 'standard' is quite complicated
>in that cables can be 'power only' and in that case there may be
>resistors across pins to indicate this to the devices at the ends.
>
>This is only for 'old fashioned' mini- or micro-B cables, USB C is a
>whole new ball game, much more complex.
>
Indeed. A good example of how *not* to develop a protocol. Define a poor
standard to start, without a clear upgrade path, then keep piling on
complexity :(

--
W J G

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