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.
