On 2018-09-27 02:37, Linus Torvalds wrote:
So it turns out that "BLE is slow" is actually the *reason* for the
problem.
There's some really odd timing thing, where when we send the read
command as two different packets (first the two command bytes, then
the 8 bytes of offset/length), and wait for the AA ACK in between,
something times out on the Mares side.
But if I send the command byte as *one* 10-byte packet, it all just
works.
Which is really strange, because the Mares app itself actually sends
it as two packets, but apparently sends them quickly enough together
that the Mares doesn't go "where's the rest?" and give up on us.
Anyway, the attached patch to libdivecomputer makes it work for me.
I'm really not all that happy with the patch, but hey, it actually
removes more lines than it adds, and it does make my loaner Mares Quad
Air happy, so it's clearly doing something good.
Jef - I assume your "send first two bytes separately" model is because
that's what the Mares app does on a serial line too, and you just
followed suite?
Unfortunately that's not the reason. Originally, I used to send
everything in one go. But for some reason that didn't work for the Mares
Matrix, and that's why I changed it to send the command in two parts.
See commit 59bfb0f3189b14ae858650b851539d59e3fefe86 for the details.
It's been a while, but I think that's indeed also how the Mares
application does it.
So I'm afraid that applying this fix, and sending everything in one go
again, will break the Mares Matrix (and maybe also some of the other
models). For the Icon HD it should still work, but that model is a bit
different from the others.
So yes, this will definitely require a lot more testing on several
models in the iconhd family before changing this.
Jef
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