[RFD] divecomputer time/date synchronization while downloading dives

[Anton Lundin]

On 19 July, 2017 - Linus Torvalds wrote:

> I'm slightly OCD when it comes to clocks. My wrist watch is one of
> those "radio time signal" ones. Seeing wall clocks that are the wrong
> time drives me wild. I just can't take it. "You have *one* job, and
> you suck at it".
> 
> When I was at the conference hotel in Beijing last month, I reacted to
> how almost *every* clock I saw was off by minutes, sometimes hours.
> The time display in the elevator? Off by a lot. The time in the room
> thermostat? Completely random.
> 
> So guess what happens with dive computers? I react to them when they
> have clocks that run slow or fast. My old Uemis would be off by
> minutes when I hadn't used it in a couple of months, and it was
> annoying to set the right time, and boy did I notice.

Fun fact is that the old OSTC mk2 / 2N / 2C computers has a setting to
fine tune the clock in it, so with some trail'n'error you can eliminate
most of the skew.

> Anyway, what this all builds up to is that I'd actually like to just
> set the time automatically when I connect the dive computer to my
> laptop (or my cellphone, for that matter - usually those end up being
> synchronized to the local time quite nicely).
> 
> And I just wrote the code for that for the Suunto EON Steel. Patch to
> libdivecomputer attached in case anybody cares (and I was happy to
> realize that it actually uses milliseconds for synchronization, but
> then noticed that it may be just a protocol thing, and the extra
> precision may get thrown away).
> 
> But I suspect people will hate that patch because it does that time
> sync thing *unconditionally*. It would be good to have a check-box and
> some way to actually set the "sync time" flag. But for that to happen,
> we'd need not just the UI side, we'd need to have the libdivecomputer
> interface too.
> 
> And yes, I know about "configure dive computer" and the "sync time"
> hack there. But it's really an ostc-specific hack, not something that
> can be used in general to synchronize the clock.

I almost always verify / update the settings in my dive computers via
that feature before a trip, and as a part of that synchronize the clocks.
 
> Thus the "request for discussion". I'd love to be able to pass in
> flags like this to dc_device_open() or add a sane
> "dc_device_set_feature()" interface or something..

I'm more inline with Jef here. Why just not make it a standard interface
which the different backends can implement?

That way it's easy for subsurface to have a to checkbox (or maybe always)
synchronize the clocks.


//Anton


-- 
Anton Lundin	+46702-161604