Scott Alfter  wrote:
> In article , Chris Green  
wrote:
> >All I'm saying is that the USB standard doesn't provide even 2 amps.
> >Thus a 'USB' cable that conforms to the USB specification doesn't need
> >to be able to carry that much current.
> >
> >If a Pi requires more than the USB specification allows then its power
> >supply *and* cable are "more than USB".
>
> We blew past the 500 mA limit long ago, well before the introduction of the
> Raspberry Pi.  The iPhone was out 5 years earlier and needed 1 A for
> full-rate charging.  By the time the Raspberry Pi was introduced, there was
> a rather large field of devices needing 1, 1.5, 2, or more amps to run
> and/or charge.  The tricks used to signal current draw with only passive
> components have even been added to the USB specs, so they really aren't
> "more than USB," as you put it.
>
No, but a USB 2.0 cable that also has data lines really only has to
carry 500mA to be 'to spec.'.  As you say lots of tricks (I'd call
them bodges personally) have been added to the USB spec.  to handle
all the various power requirement additions but to expect any/all
cables to be able to handle them all is a bit hopeful.

All I was originally pointing out was that it's (very) often the cable
is the issue when running a Pi, you can have a very capable power
supply but if the cable isn't good enough it's not going to work
reliably.

--
Chris Green
·

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