can't download Oceanic VT3 on linux

[Jef Driesen]

On 2014-03-10 14:18, Hamish Moffatt wrote:
> On 07/03/14 20:15, Jef Driesen wrote:
>> 
>> 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
>> 
> Just back from a holiday weekend including a dive. The test build runs
> well, though slowly. So far over 700 seconds, with only one error
> being:
> 
> [68.234123] ERROR: Unexpected answer start byte(s). [in
> ../../source/src/oceanic_atom2.c:340 (oceanic_atom2_send)]
> 
> If you want to send me a patch or tell me where to add the delay, I
> can rebuild the source and play with timing and see what works for me?

The slowness is expected. The attached patch introduces a 100ms delay 
before each command. With 4096 packets (of only 16 bytes), that means a 
total delay of at least 409.6 seconds. That alone is already a very good 
reason not to apply this patch, especially because most users don't need 
it. But it does give a good indication that the real problem is likely 
something timing related. The question is of course what and where.

Something else that is worth trying is increasing the 100ms delay in the 
oceanic_atom2_device_open() function. I don't really understand why, but 
some interfaces seem to need some extra time between setting up the 
serial port and sending the first data packet. I suspect that the OS or 
driver is async and returns before the settings are actually applied, 
causing us to send data before the device is ready. But I'm not really 
sure about that. Anyway, adding some extra delay there isn't that much 
of a problem because it's just a one time delay.

Jef
-------------- next part --------------
A non-text attachment was scrubbed...
Name: atom2.patch
Type: text/x-diff
Size: 466 bytes
Desc: not available
URL: <http://libdivecomputer.org/pipermail/devel/attachments/20140310/7f6368fc/attachment.patch>