messing with the gas / tank handling

Linus Torvalds torvalds at linux-foundation.org
Tue Oct 28 16:47:31 PDT 2014


On Tue, Oct 28, 2014 at 4:24 PM, Dirk Hohndel <dirk at hohndel.org> wrote:
>
> I know we tested this with the Uemis and that simply switched between
> sensors in the samples.

Right. The Uemis wasn't a reason to switch from our current sensor idx
+ pressure model.

> I can't remember what the Mares did, though.

Did we even have multiple sensors?

> How many tank sensors does the EON Steel support? The Uemis supports up to
> three.

I think the docs said "up to ten".

> 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.

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.

In fact, the EON Steel uses a 16-bit centibar representation for its
cylinder pressure data (or "kPa", which is the same thing as cbar):

  <PTH>sml.DeviceLog.Samples.Sample.Cylinders.Cylinder.Pressure
  <FRM>uint16,nillable=65535
  <MOD>1000*x,x

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

                   Linus


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