Re: [Gumstix-users] ADC Range on robostix

[Jesse W. <jes...@gm...>]

>
>
> Since AREF is hard-wired to 5v, you can only use 5v as the input.
>
> You can use the ADC in 8-bit or 10-bit mode, so the range will be
> 0-255 or 0-1023 depending on how you set things up.




Just found out that there is an internal ref of 2.56v that you should also
be able to use......would give you a little bit better accuracy I should
think.

This is from page 238:
The reference voltage for the ADC (VREF) indicates the conversion range for
the ADC. Single ended channels that exceed VREF will result in codes close
to 0x3FF. VREF can be selected as either AVCC, internal 2.56V reference, or
external AREF pin.

So i guess my question is: Why should AREF be wired to 5v when we can
already do that in the ATmega? It would be better to break AREF out to a pad
on the back I think. I guess if you were daring you could cut the trace and
wire in the voltage you wanted to the foot on the chip.....
-- 
        -Jesse W.