Mares Smart Dive Computer + Bluelink pro

[Linus Torvalds]

On Thu, Sep 27, 2018 at 9:30 AM Linus Torvalds
<torvalds at linux-foundation.org> wrote:
>
> I wonder if bluetooth needs to lower the size of the maximum read packet.

Hmm. Again, the Mares app definitely does 256-byte reads too.

So once more, I'm thinking it's some oddity where the bluetooth side
is very slow (the timestamps seem to show bursts of four packets with
delays of half a second or a second between bursts).

And what may end up happening is that when the bluetooth side is slow,
the buffer on the BlueLink fills up from the serial data and you have
buffer overflows, and then things go sideways very quickly.

Judging by the fact that we did get 250 bytes, I wonder if the buffer
size on the BlueLink is perhaps around 256 bytes.

I still think the fundamental issue is some odd BLE slowdown (that
pattern of half-second and second delays between bursts of four
packets really makes me go "Hmm"), but making the libdivecomputer
Mares backend use a smaller packetsize might work around the problem.

Maybe the blue light is "packet retransmission". Because yes, I see
the the same "mostly blinking green, sometimes blue flashes" behavior
on my BlueLink.

                  Linus