Accessing Petrel downloads and events

[Jef Driesen]

On 2018-02-28 11:52, Willem Ferguson wrote:
> 1) In both CCR mode as well as SCR mode, the Petrel 2 allows switching
> between OC bailout gases and CC gases. This done by performing
> selecting either  BO->SC  or  SC->BO from the Shearwater menu. These
> events must be recorded in the dive log but are presently not easily
> accessible, at least from within Subsurface. How does libdivecomputer
> see the events? Is there any way to acces them from Subsurface?

There is an OC/CC bit in every sample. It's currently only used for 
enabling/disabling the ppO2 and setpoint samples. But the value itself 
(or a change of the value) is not reported.

> 2) Shown below is the Subsurface log trying to download a Petrel 2
> dive into a dump for better analysis. However, every time I try this,
> the download aborts. With the "Save dumpfile" and Save logfile:
> options NOT checked, the download goes flawlessly.

The Petrel protocol doesn't support downloading memory dumps.

(1) Download a memory dump using the older predator protocol. This 
protocol supports memory dumps, but the drawback is that not all 
information will be downloaded this way. Only the most recent dives are 
accessible and even the dives that can be downloaded have some 
information removed. (The Petrel sample size is twice as large as the 
Predator samples, so some info gets dropped when using the older 
protocol.)

(2) Dump the raw data of the individual dives. Unfortunately Subsurface 
doesn't support this and you'll need to use libdivecomputer's dctool 
command-line application:

dctool -vv -l petrel.log -f petrel download -o dive.%n.bin -f raw 
<serialport>

Or as an alternative, only enable the libdivecomputer logfile checkbox 
(but NOT the dumpfile checkbox). I can extract the raw data from the 
logfile.

> One thing to notice is the warning below:
> 
> WARNING: Disabled all O2 sensors due to a default calibration value.
> 
> This is despite explicit calibration before the dive. This is similar
> to your issue with my Predator download, previously discussed.
> Unfortunately the Predator is in the UK at present, so I could not do
> an analogous download from that dive computer.

This warning means that all O2 sensors are marked as being calibrated in 
the data, but the calibration values are left at their factory default 
settings. So the sensors were probably calibration (as you confirm), but 
for some reason the calibration values are not stored. And thus we can't 
convert the ppO2 data from millivolt to ppO2.

Do you have a divecan unit? I believe Anton mentioned a while ago that 
he suspects the calibration might be done a bit different there. In a 
way where the dive computer gets the ppO2 values directly and thus 
doesn't need the calibration values. But only the millivolt values are 
stored, but we can't convert them to ppO2 without the correct 
calibration values.

So this warning means you won't get any ppO2 samples from 
libdivecomputer.

Jef