The new gasmix sample contains the index of the active gas mix.
This new sample is intended as a replacement for the existing gas change
events (SAMPLE_EVENT_GASCHANGE and SAMPLE_EVENT_GASCHANGE2). To maintain
backwards compatibility, the legacy events are marked as deprecated but
not removed yet.
The Shearwaters store the current dive mode for each sample, and not one
single value for each dive. Therfore we need to process all samples. If
there is at least one sample marked as closed circuit, we classify the
dive as a closed circuit dive. Otherwise we default to open circuit.
Gas mixes that have been disabled are stored as a mix with 0% oxygen and
0% helium. This is clearly an invalid gas mix, and it makes no sense to
return it back to the application.
In the public header files, all symbols are marked extern C. When using
a C compiler, there is usually no problem if the header isn't included
in the C file. But the msvc build system uses the C++ compiler (due to
the use of some C99 features not supported by the msvc C compiler).
There are two good reasons for this change. First of all, it makes the
Predator data format more consistent with the Petrel data format, which
also has the final block appended to each dive. But even more important
is that we might actually need the information stored in the final block
someday.
The final block contains important information about the device, such as
the firmware and logbook version. Right now this information is simply
lost after the download. But if the data format ever changes to support
some new feature, we'll likely need that information to autodetect the
correct format.
Unfortunately this also changes the dive format in a non-backwards
compatible way. However, to minimize the inconvenience, the legacy
format (without the extra final block) remains supported in the parser.
The Petrel (with updated firmware) supports an enhanced communication
protocol, which is more efficient and powerfull than the legacy Predator
compatibility mode. The new protocol uses data compression for faster
transfers and supports the ability to selectively download individual
dives. Last but not least, the new protocol isn't limited to the last
128kB of logbook data, but can access the full logbook capacity (16MB).
Currently, each backend has it's own function to verify whether the
object vtable pointer is the expected one. All these functions can be
removed in favor of a single isintance function in the base class,
which takes the expected vtable pointer as a parameter.
Functions which are called through the vtable, don't need to verify the
vtable pointer, and those checks are removed.
The term "backend" can be confusing because it can refer to both the
virtual function table and the device/parser backends. The use of the
term "vtable" avoids this.
Having these as events seems less useful since for many dive computers
there are data with every sample - so it makes much more sense to have
these as part of the sample.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
So far only OSTC and Shearwater Predator are supported. For the OSTC we
support CNS and setpoint changes in the samples (the current hardware
doesn't actually support ppO2 sensors and for the older hw that does I
don't have the correct encoding information).
For the Predator we support only the "average ppO2 during the sample".
The Predator also gives us a CNS value at the end of the dive - I don't
quite know yet how to deliver that back to the consumer. Possibly as CNS
value in the very last sample? That would at least be consistent.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
The Shearwater Predator has two different sets of gas mixes for OC
(Open Circuit) and CC (Closed Circuit) mode. Since the dive mode can
be switched during the dive (e.g. in a bailout scenario), there is no
easy way to select one of both sets. With this change, both sets are
returned. It's not a perfect solution, but for CC dives it's already
an improvement.
