OSTC over BLE experiences and questions

Linus Torvalds torvalds at linux-foundation.org
Tue Jul 11 18:41:06 PDT 2017


On Tue, Jul 11, 2017 at 5:32 PM, Matt Thompson <mathomp at gmail.com> wrote:
>>
>> So I was singularly unimpressed. I had it with me for one dive trip
>> and never touched it again.
>
> Well I'm doing my first real dives with it tomorrow so I'll see how it goes.
> I've done a few lake dives with it and the information on the main screen is
> good.  The compass is useless and the reflection is annoying.  I'm DM'ing at
> an Aqualung shop so it's part of the "uniform."

So I just googled the i750TC images, and it actually looks a bit
different from the A300CS.

For example, one of my complaints about the A300CS was that it didn't
even show dive time on the primary screen, and you had to go to the
secondary screen (with the small font) to see that. That was just
crazy bad.

I absolutely require a few main things that an air-integrated dive
computer should show without extra key presses:

 - depth and dive time (duh!)
 - deco state (NDL when not doing deco, ceiling and tts when deci)
 - cylinder pressure and "gas time remaining" estimate

and the A300CS literally missed that dive time thing. I don't know how
you can design a dive computer that doesn't show dive time.

(There are other things I like to see, but they should be in smaller
text or might be behind a button: time-of-day, gas mix, compass
bearing, things like that)

The i750TC has fixed that, according to the screenshots I saw. It has
all those (and apparently time-to-surface even when in no-deco mode,
which sounds fine and might make the switch to deco mode less
jarring).

So my main "WTF?" complaint is gone right there.

If it also doesn't have quite as reflective a screen, it might
actually be a nice dive computer.

(The reflective screen is obviously only a problem in bright sunlight,
but it was really _so_ reflective that it was actually hard to see
even at 30ft under some conditions. At the safety stop it was just
really bad - imagine having to dive upside down just to see the
screen).

The i750TC also looks a bit better - it doesn't have the gaudy chrome
accents that the A300CS did.

So it's clearly a _related_ dive computer with a lot in common, but
it's not the exact same thing.

And yeah, the compass on the A300CS was an annoying mess, and didn't
work as a compass at all. The interface was *so* jerky and so ugly and
incomprehensible that it just not usable. It sounds like the i750TC
didn't fix on that part.

>> Annoyingly, it seems like I have lost the tank sensor for it. And I'm
>> annoyed mainly because I think that tank sensor would work with my
>> Perdix AI.
>
> If you can find it I can confirm that it is exactly the same sensor and it
> does work with the Perdix AI.

Now I'm just doubly annoyed that I can't find it ;)

>> The good news is like the OSTC3 chip, that nBLUE chip is actually
>> documented, because it's used in various random IoT projects. For
>> example
>>
>> http://www.byteworks.us/Byte_Works/Blog/Entries/2012/12/28_Build_Your_Own_Bluetooth_low_energy_based_circuits_using_the_Blue_Radios_BR-XB-LE4.0-S2.html
>>
>> Can you verify that the nRF information from your i750TC matches the
>> UUID's on that web page? Because that's what my A300CS had - if they
>> are different, we're not going to have exactly the same BLE code..
>
> I looked and I could not find a matching UUID in the bunch.  I never could
> get my i750 to bond with the nRF tools so it might not be good information
> but...

No, according to your screenshots it doesn't have that same BLE chip
that I have in my A300CS.

So it's not just a slightly different shell and firmware, there's
likely some real hardware differences. It's probably almost identical,
though.

Sadly, a bit of googling did not find that uuid that it reports, so
the exact details of the i750TC will need to be determined the hard
way with testing and luck.

                    Linus


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