sample rate drift increased over last few days -> FTDI Latency

AraleArale
edited September 2015 in Software
Hi everybody,

I noticed something strange on my setup.

I'm using Openvibe for a few weeks, great software by the way.
When I started the connection in the acquisition server the device drift was around 0.50ms, since a few days it's between 2ms and 6ms.
The refreshing rate is then much slower in the designer part of Openvibe. I'm still able to get data from the electrodes but the acquisition rate is slow.
I also notice in Openvibe after pushing "play", just below the device drift feedback, it was written "sending... 1 host connected", now I have "sending... 0 host connected".
This is very strange, I didn't do anything special. I first reflashed my openbci32bit but it was still slow. I also installed Openvibe on a different computer, removed and reinstalled the driver of the dongle on my PC, nothing changed back.

I also checked the connection with the Processing IDE but I had the same problem. The battery is fully charge.
I'm using the last code for both host and device RFduino and I'm flashing the 32 bit micro with the last arduino IDE trick.
After a few days checking everything I'm a bit lost, I probably did something but I can't find what... Maybe one of you could give me some clues?

Thanks a lot for your support!
Arale

Comments

  • wjcroftwjcroft Mount Shasta, CA
    Arale, hi. You did not mention if you had checked your FTDI driver latency setting,

    http://openbci.com/forum/index.php?p=/discussion/200/latency-timer-windows-control-panel-setting

    Perhaps it's possible that Windows might reset this to defaults under odd conditions.

    Are you saying the GUI does not work at all? Or that you see pauses, bursty-ness? Or that the entire sample rate seems to be consistently less than 250 sps (4 ms per sample).

    I'm also going to mention Jeremy @jfrey here, who wrote the OpenViBE driver and has the most experience.

    Regards, William

  • wjcroftwjcroft Mount Shasta, CA
    I also see that FTDI did a new Windows driver release in late July. If Microsoft then "pushes" that out to end users on some kind of automatic basis -- there may be some correlation with this newest driver.

    http://www.ftdichip.com/Drivers/VCP.htm

    Can you check your Device Manager control panel and see what version you are running. Also what Windows OS. You might try a Linux test as well.
  • jfreyjfrey
    Since I'm summoned by William I will write a quick comment: the "XX host connected" depends on the number of scenarios launched (i.e. the number of "acquisition client" boxes actually running). I'd have to check, but I have the impression that the evaluation of the drift in the acquisition server is a bit off when there is no client connected. However this does not explain why you would have issues as well with the Processing GUI, hence the FTDI driver seem a good lead (do try on linux with a bootable USB key).

    [vanishes in a cloud of smoke]
  • AraleArale
    William, Jérémy thanks!

    Version 2.12.00 of the driver was installed, I don't know if the system did an auto update. Anyway I tried the last one (2.12.06) and the previous one available on the FTDI website (2.10.00 and 2.08.30) but nothing fixed the problem.

    I then changed the latency time to 1sec as you proposed and now it's working fine.
    This is a bit strange since it was OK a few days ago with the latency at 16ms but the important point is that everything is OK now (on both Openvibe and the Processing GUI).

    And yes sorry Jérémy, you're right as soon as the scenario is launched I can see that 1 host is connected, didn't notice it before.

    Thanks again.
    Arale.
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