Re: ADC setting for differential and single-ended channels

[Mario Domenech Goulart <mario@ossystems.com.br>]

Hi Lars,

On Thu, 18 Jul 2013 15:54:03 +0200 Lars-Peter Clausen <lars@metafoo.de> wrote:

> On 07/18/2013 02:02 PM, Otavio Salvador wrote:
>> On Thu, Jul 18, 2013 at 2:50 AM, Lars-Peter Clausen <lars@metafoo.de> wrote:
>>>
>>> Well the standard API as Jonathan said is to expose all possible pin
>>> combinations. In this case that might be up to 8x8=64 channels. In my
>>> opinion that's fine, but on a specific board maybe not all combinations are
>>> valid. So you might want to specify in your platform data or devicetree that
>>> only a subset of these 64 channels is valid and should be exposed to
>>> userspace. In my opinion it makes the most sense to handle this in the IIO
>>> core since this is a generic requirement, nothing specific to this chip.
>>> E.g. even for 'simple' converters you'll find situations where some pins
>>> might not be connected.
>> 
>> Right and how should we do this?
>> 
>> Because it would not be 8x8 but it has also the single-ended
>> combinations (using different N inputs).
>
> Does the device really support single ended, it looks to me as if it only
> supports pseudo-differential configurations.

That's not very clear to me either.  The datasheet states the chips have
single-ended inputs, but the mux configuration always assume a positive
input and a negative input.

I'm assuming the "single-ended" mode refers to using an arbitrary input
as negative reference to all the other n-1 inputs.  I suppose that'd be
a pseudo-differential configuration, right?

Best wishes.
Mario