Re: Pressure sensors

[Artturi Alm <artturi.alm%gmail.com@localhost>]

On Wed, Jan 02, 2019 at 08:05:03PM -0500, Greg Troxel wrote:
> Artturi Alm <artturi.alm%gmail.com@localhost> writes:
> 
> > On Tue, Jan 01, 2019 at 12:03:31PM -0500, Greg Troxel wrote:
> >> So, I wonder why you are choosing kPa vs hPa, and if that choice ends 
> >> up being a framework choice for everything.  And how the rest of the
> >> world deals with this issue.
> >
> > By accident, i guess, and after having read about pascals on wiki[0],
> > it felt like a good choice, for being "not just for meteorologists",
> > nor imperial, but i'm from metric .eu, fwiw..
> 
> Interesting article, and it seems right.
> 
> Atmospheric pressure is basically meteorology, IMHO.
> 

Alone as is, sure, but here i have it on a sensor with temperature and
humidity too, and the datasheet does list only one meteorology related
typical application for it, the weather forecast, among the not as
obvious "flying toys"/"indoor navigation" etc..

> > I actually got *= 1000 for mPa in the driver, so i don't really care
> > about the unit to be used, as long as it's not loosing any precision/
> > limiting range (for kernel -> user, so Pa would work just as well, and
> > i'm not sure whether mPa does buy anything w/r.t. future sensors, it
> > was more about minimal diff looking reasonable).
> 
> The comments about integers, range and precision are compelling.  It's
> hard to imagine anything in envsys delivering more than 1 Pa of
> precision.
> 
> I didn't mean to give you a really hard time about this.   It just felt
> like a decision that was likely to control how all envsys pressure
> reporting is done in NetBSD, for all time.  But maybe I'm misperceiving
> that.
> 

Much appreciated, somehow i wasn't thinking of this as a part of any
API, while i know it kind of is, so better indeed to get it right :]

-Artturi