can't download Oceanic VT3 on linux

[Jef Driesen]

On 2014-03-07 08:30, Hamish Moffatt wrote:
> On 07/03/14 18:23, Jef Driesen wrote:
>> On 2014-03-07 03:20, Hamish Moffatt wrote:
>>> I'm trying to download from my VT3. I've built libdivecomputer 0.4.2
>>> on Linux (64-bit) but downloading is very slow and eventually fails.
>>> I've tested with both Subsurface and using the "universal" example. 
>>> It
>>> does retrieve some dive data ok though.
>>> 
>>> Downloading my VT3 does work on Windows though, using Diving Log 5.0
>>> (includes libdivecomputer 0.4.2, 32-bit) or the "universal" app 
>>> binary
>>> which I downloaded directly from the libdivecomputer.org site.
>> 
>> I'm a bit surprised it works on Windows, but not on Linux. Because the 
>> code is the same, except for the low-level serial code, that might 
>> indicate a problem with the driver rather than the dive computer.
> 
> I wasn't able to run your pre-compiled universal binary on linux
> unfortunately as it requires GLIBC_2.14 (my Debian 7/wheezy has 2.13).
> I'm using the same cable on Windows and Linux, though they're
> different computers.

I have fixed that. I have build a 32bit version again. (I've always done 
32bit builds in the past, not sure how that suddenly changed.)

>>> Any suggestions?
>> 
>> Does your dive computer have a low battery? It's pretty common reason 
>> for failing downloads. Typically the PC interface requires more power 
>> than during diving. Another thing is to avoid using USB hubs and 
>> connect directly to a USB port on the PC.
>> 
> I replaced the dive computer battery a couple of weeks ago.

So that should be good then.

> I've connected it directly to the front panel USB slots on the
> computer, and also via the hub in my monitor. I can try directly into
> the back of the PC later, but I wouldn't think that would change
> anything.

That's unlikely to make a difference. The hub in the monitor could make 
things worse, so if possible avoid that.

One of the problems with usb-serial converters, compared to real serial 
ports is the increased latency. With a timing sensitive protocol (which 
the Oceanic is not) that could cause problems. You can find a good 
explanation here:

http://projectgus.com/2011/10/notes-on-ftdi-latency-with-arduino/

You could try to adjust the latency as described there, although I doubt 
that is the problem.

I have also prepared a new build which slows down sending the commands 
by waiting 100ms between the packets. I have the impression we might be 
sending commands too fast for your device. Can you give this a try?

wget http://www.libdivecomputer.org/builds/experimental/linux/atom2
chmod +x atom2
./atom2 /dev/ttyUSB0

> I forgot to add that one of the failed download attempts left the VT3
> displaying "BSL" which I gather means it's in the bootloader expecting
> new firmware. Seems there's some pretty serious corruption going on.
> 
> What baud rate is used? Flow control issues? Some other setting wrong
> by default?

If that would be the problem, then it would fail on Windows too, because 
the same settings are used on all platforms.

Jef