Not long ago, I asked this questionhttps://superuser.com/a/1018115/380110 about whether or not USB includes signals for the amount of power delivered.
I received this amazing answer from @txtechhelp.
That leads me to another question. I bought a high-end (not a cheapie) 2.1A (x2) USB Auto Adapter. When I plug an HP Touchpad tablet into it, the Touchpad complains that insufficient energy is being delivered. I tried a few other 2.1A auto adapters, and the Touchpad complains about insufficient energy for all of them as well.
Given the info gleaned from @txtechhelp's answer, combined with the fact that the Touchpad only needs 2A at 5V, something is not making sense.
I think it may something to do with the info in this thread, that indicates that there are a pair of resistors in the Touchpad that are not part of the USB standard, but I honestly did not understand it fully.
Why does the Touchpad indicate that it is not receiving enough energy despite trying multiple 2.1A USB auto adapters?
UPDATE:
The term "auto" adapter can have multiple meanings. To clarify, I mean "automobile" adapter (aka "cigarette lighter adapter"... but who smokes anymore?).
I ran all testing with the vehicle engine turned on.
I performed all testing with the same USB cable, but that cable is known to work. If there is a reason why a known cable would work for some power levels, but not others, please educate me as to why!
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