On Wed, 14 Aug 2024 15:02:42 +0200 "Esteban Blanc" <eblanc@xxxxxxxxxxxx> wrote: > On Sat Jun 29, 2024 at 6:40 PM CEST, Jonathan Cameron wrote: > > On Thu, 27 Jun 2024 13:59:11 +0200 > > Esteban Blanc <eblanc@xxxxxxxxxxxx> wrote: > > > > > This is adding DT bindings and a new driver for AD4030, AD4630 and > > > AD4632 ADCs. > > > > > > This work is being done in collaboration with Analog Devices Inc., > > > hence they are listed as maintainers rather than me. > > > > > > The code has been tested on a Zedboard with an EVAL-AD4030-24FMCZ, > > > an EVAL-AD4630-24FMCZ and an EVAL-AD4630-16FMCZ. As there is no eval > > > board for AD4632 the support can't be tested at the moment. The main > > > difference is the reduced throughput. > > > > > > This series is taged as RFC because I think I'm misusing > > > IIO_CHAN_INFO_CALIB*. For CALIBBIAS the doc in sysfs-bus-iio says > > > "Hardware applied calibration offset (assumed to fix production > > > inaccuracies)" but AD4030 offset in on 24bits and I would argue that at > > > this point it's not just here to fix production inaccuracies. Same this > > > for CALIBSCALE. What IIO attributes should I use instead? > > > > Interesting. So awkward question for you. What's the point in applying > > a digital offset? calibbias is normally about tweaking the Analog side. > > This just seems to be adding a value on. I'm not sure it affects what > > can actually be captured without saturation. > > True, both scale and offset applied with thoses registers can lead to > saturation. > > > Maybe it has influence by changing the input range and scale for the > > block averaging filter? I'm not sure. > > > > You can use offset for this given it's a simple linear value and not > > anything to do with calibration. It's a little awkward though as that > > is post scale rather than the other way around which is rather more > > common. > > Controls are in the form > > voltage = (raw + offset) * scale > > > > So here > > voltage = (raw + offset_reg / (gain_reg * other scaling)) * gain_reg * otherscaling. > > > > Hence your offset is a bit fiddly to compute. > > After talking to ADI engineer about this, the conclusion is that I was > wrong and this is indeed mostly for calibration. They left the range > of values quite wide in case a user wanted to use this to apply an > offset or scale to the raw value directly in order to avoid doing some > post processing later on. But the main goal is calibration. > > If that's ok with you I will keep CALIBBIAS and CALIBSCALE for the next > round and remove the RFC tag. Sure. Bit odd to do this post processing on device but I guess it made sense for some customers. Jonathan > > Thanks for your time and sorry for the confusion, >
