On Sat, Feb 17, 2024 at 10:25 AM Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > > On Fri, 16 Feb 2024 10:57:33 -0600 > David Lechner <dlechner@xxxxxxxxxxxx> wrote: > > > On Fri, Feb 16, 2024 at 8:22 AM Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > > > > > > On Thu, 15 Feb 2024 11:13:19 -0600 > > > David Lechner <dlechner@xxxxxxxxxxxx> wrote: > > > > > > > ... > > > > > > > > > > Tables 22, 23 and 24 in the AD7194 datasheet show that this chip is > > > > much more configurable than AD7192 when it comes to assigning > > > > channels. There are basically no restrictions on which inputs can be > > > > used together. So I am still confident that my suggestion is the way > > > > to go for AD7194. (Although I didn't actually try it on hardware, so > > > > can't be 100% confident. But at least 90% confident :-p) > > > > > > You would have to define a channel number for aincom. There is an explicit > > > example in the datasheet of it being at 2.5V using a reference supply. > > > > > > I wonder what expectation here is. Allways a reference regulator on that pin, or > > > an actually varying input? Maybe in long term we want to support both > > > options - so if aincom-supply is provided these are single ended with > > > an offset, but if not they are differential channels between channel X and > > > channel AINCOM. > > > > > > Note though that this mode is described a pseudo differential which normally > > > means a fixed voltage on the negative. > > > > > > So gut feeling from me is treat them as single ended and add an > > > aincom-supply + the offsets that result if that is provided in DT and > > > voltage from it is non 0. > > > > Calling AINCOM a supply doesn't sound right to me since usually this > > signal is coming somewhere external, i.e. you have a twisted pair > > connected to AIN1 and AINCOM going to some signal source that may be > > hot-pluggable and not known at compile time. As an example, if AINCOM > > was modeled as a supply, then we would have to change the device tree > > every time we changed the voltage offset on the signal generator while > > we are testing using an evaluation board. > > We tend to stick away from designing features to support testing with > devboards where external wiring is involved because anything could be > wired up there. (Examples are things like shunt resistors - normally > they are DT only) So sometimes it's a bit painful to work with such boards. > The main focus has to be production devices or at least stable set ups > where a fixed DT is sufficient. > > So I'm more interested in focusing on production device use cases. > Do we have an information on how this is this used in those environments? > Point taken. I also checked with an apps engineer at ADI and it does sound like AINCOM should be a supply.
