messing with the gas / tank handling

[Dirk Hohndel]

On Tue, Oct 28, 2014 at 04:47:31PM -0700, Linus Torvalds wrote:
> 
> > I can't remember what the Mares did, though.
> 
> Did we even have multiple sensors?

I could have sworn that we had two. I even remember talking to the Mares
guys about it. But I can only find one.
Does anyone have a spare Mares Icon HD transmitter that they wouldn't mind
borrowing us for a while? Or does anyone here have an Icon HD with two
transmitters from which we could get raw data?

> > How many tank sensors does the EON Steel support? The Uemis supports up to
> > three.
> 
> I think the docs said "up to ten".

Wow. We need to increase MAX_CYLINDERS :-)

> > Do we really need 4 bytes for pressure data? Yes, we do when saving in
> > mbar... we could switch to storing things in cbar - unsigned int16 gives
> > us up to 650 bar...
> 
> Hmm. Looking at the sample pressures I have, none of them have higher
> resolution than centibar anyway. So we could do that for
> cylinderpressure. But I only have a few pressure sensors and sources
> of data: the Uemis, and two different versions of the Suunto one.

I did a quick look through libdivecomputer sources. I cannot find any
device that appears to devote more than 16 bits to this. And I actually
find several that appear to do this in 8 bits (i.e., 2 bar resolution).

> The surface pressures and cylinder working pressures are actually
> saved in mbar, though, so we'd have to use a separate type for
> cylinderpressure. Might not be a bad idea, though.

I'm really torn. Do we really care that much? This would be our third
pressure type. We have pressure_t which is 32bit mbar, we have
o2pressure_t which is 16bit mbar. And then we'd have cylpressure_t which
is 16bit and cbar.

> so at least *one* divecomputer clearly thinks it's sufficient.

As far as I can tell ALL divecomputers think that's sufficient.

/D