[Arm-netbook] [eoma68] mini desktop pc

joem joem at martindale-electric.co.uk
Thu Dec 5 09:22:04 GMT 2013


>  in case that is not clear, that is "high" voltage of 2.0 volts,
> threshold of 1.4 V and "low" voltage of 0.8 V.
> 
>  is that clear?


Still feeding the confusion.

A pull up point and pull down point has nothing to do with voltages.

 e.g. if you remember HNO's fix for RS232 problem.
 It requires connection to the pull up point. It was labelled
 as the 3.3V line - with the implicit meaning that it was the pull up
 point that all EEs would know about.
 (All EEs would also implicitly know that connecting to a substitute
  arbitrary 3.3V point is utterly meaningless.)

 So, without a pull up point for GPIO lines,
 certain types of electrical and electronic
 problems cannot easily be solved.

Instead of calling it 3.3V line, you could call it GPIO_PULL_UP line
and then no one has to know what voltage its running at,
and implicitly also beneficially assume they cannot draw
power from that line, or rely on it being 3.3V in the future.







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