Jinx wrote:

>> You assume reading 000 corresponds with the interval centered
>> around 0V, but in fact it is the interval that starts at 0V
> 
> Ah, so you mean the interval starting at 000 is the 1st, starting at
> 001 is the 2nd, therefore the 1024th interval starts at 3ff. That
> corresponds with what Gerhard quoted
> 
> Vin < 1 Lsb: ADCOut=0
> Vin < 2 Lsb: ADCOut=1
> .
> Vin < 1023 Lsb: ADCOut=1022
> Vin < 1024 Lsb: ADCOut=1023
> 
> I was originally thinking along the lines of gaps between posts,
> with the last post being the absolute limit
> 
> Think I'm clear about it now. So I have been using the ADC
> correctly all along

The term "steps" that has been used in this thread seems to be an imprecise
concept. You have level intervals (that's usually a power of 2) and you
have transitions between them (that's level intervals - 1). The ADC output
is correspondent to the level intervals. 

The voltages corresponding to the level intervals against the output is
called the ADC transfer function or something similar. In ADC datasheets
you find that. There are several possibilities, and which one it is depends
on the ADC implementation. The above transfer function is common (and seems
to apply to all PIC ADCs), but it's not the only possible one.

Gerhard

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