Divecomputer-reading from Mobile devices (Was: Divemate Fusion)

Miika Turkia miika.turkia at gmail.com
Sun Apr 10 01:05:12 PDT 2016



> On 10 Apr 2016, at 02:19, Dirk Hohndel <dirk at hohndel.org> wrote:
> 
> 
>> On Apr 9, 2016, at 3:27 PM, Martin Gysel <me at bearsh.org> wrote:
>> 
>> Am 09.04.2016 um 23:55 schrieb Dirk Hohndel:
>>>> On Sat, Apr 09, 2016 at 02:46:32PM -0700, Linus Torvalds wrote:
>>>>> On Sat, Apr 9, 2016 at 1:59 PM, Dirk Hohndel <dirk at hohndel.org> wrote:
>>>>> 
>>>>> It would be equally easy to build a full Subsurface - we seem to have a
>>>>> pretty complete Debian distro here.
>>>> 
>>>> Well, there's only 4GB of emmc flash (and 512MB RAM) on that thing, so
>>>> I think it would be cramped to actually build subsurface on it.
>>>> 
>>>> But yeah, you don't actually want a UI, you really just want a process
>>>> that links to libdivecomputer and can communicate over bluetooth to
>>>> get commands and return results.
>>> 
>>> I have a simple BLE app but can't quite connect to it, yet. But I'm pretty
>>> sure that this is just a matter of reading the docs one more time :-)
>> 
>> keep in mind, the throughput of a BLE connection is quite limited
>> (~32kbps on iOS, maybe up to ~84kbps on Android [1]). to download more
>> than a couple of dives a wifi connection might be the better option.
>> furthermore already used technology like git could be used to transfer
>> the dive from the 'device' to the mobile or to the cloud directly. BLE
>> could be used to command it.
> 
> Yes, now that I have a working BLE connection from the C.H.I.P to my iPhone I would have to agree - it's not exactly fast.
> But then again, the information we need to transfer isn't all that large, either. The compressed XML for me seems to average under 4kB per dive/divecomputer. That seems to imply that we could transfer a dive every couple of seconds or so. Definitely worth to play with. I'd much rather not mess with a wifi connection if I can avoid it. Since we can't assume that public wifi is available for the C.H.I.P to connect to we'd have to create a point to point wifi connection with the phone / tablet. Messy, complicated, error prone.

If the CHIP acts as a wifi access point, the setup should be quite easy. Just need to initially configure wpa passphrase on the device and connect to it using mobile/laptop/whatnot. I have had too many problems with bt connections to count it reliable but wifi works generally quite well.

miika 


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