[linux-cirrus] Re: edb9302 ADC
- From: john reynolds <jjreynolds2004@xxxxxxxxx>
- To: linux-cirrus@xxxxxxxxxxxxx
- Date: Tue, 14 Jun 2005 13:44:41 -0700 (PDT)
> john cooper <john.cooper@xxxxxxxxxxx>
>Just a quick thought -- ADC channels [1,2,3] are
>documented in the errata as having linearity
>problems and are unusable. Apparently channels
>[0,4] are functional. This is r/w/t mask E0.
John,
We're aware of the probs and plan on using
just 2 channels. One of the HW guys I work with
showed me the HW spec for the ADC.
With the input from 0 to Vref/2 you get result values
~9E58 to FFFF.
With inputs from Vref/2 to Vref you get result values
from 0000 to ~61A8. It seems like it's a 15 1/8 bit
ADC :)
This means you have to read the lower 16 bits of
the result reg, not the lower 12 as the user guide
states. Also you have to delay at least 500us after
setting the switch reg according to the HW spec.
John
Send lawyers, guns and money. The shit has hit the fan ...
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