On Mittwoch, 26. April 2017 08:59:47 CEST Jonathan Cameron wrote: > On 26/04/17 07:19, Jonathan Cameron wrote: > > On 17/04/17 23:08, Stefan Bruens wrote: > >> On Freitag, 14. April 2017 17:12:03 CEST Jonathan Cameron wrote: [...] > > > >> 4. Any user of the gain settings had to be made aware of the possibility > >> to > >> change it, no matter how it is exposed. Making it part of the scale, and > >> thus changing the meaning of the raw values, would be breaking the > >> existing ABI.> > > The raw values should indeed not change. That was a missunderstanding on > > my part. Usually when a device has a PGA it is not compensated for in > > the output. So normally it's up to the driver to 'apply' the effective > > gain to the incoming reading. When that isn't the case, it can be > > considered some sort of internal trim - hence the use of calibscale for > > this case. > Mulling this over, calibscale might not work either in this case. The > datasheet helpfully sometimes uses ranges and sometimes uses scale factors. > There is also obviously the calibration register kicking around which would > also be handled with calibscale if exposed to userspace (currently it isn't) > > I'm out of time tonight so will think it bit more about this and get back to > you in the next few days... hardwaregain may be a viable option. For the shunt voltage, available values would be [0.125, 0.25, 0.5, 1.0], for the bus range we would have either [0.5, 1.0] or [1.0, 2.0] for bus ranges [32V, 16V]. Does hardwaregain have the right semantics for shunt voltage gain and/or bus range? Kind regards, Stefan -- Stefan Brüns / Bergstraße 21 / 52062 Aachen home: +49 241 53809034 mobile: +49 151 50412019 work: +49 2405 49936-424 -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
