Daisy module signal amplitude incorrect when saving to SD card

armz12armz12
edited August 2016 in OpenBCI_GUI
I'm using the 32bit OpenBCI 16ch kit.  I am recording all 16 channels with a single ground and reference that are connected to both the main and daisy boards with a y-cable.  When saving the data to the SD card, the amplitude of the signal recorded on the daisy channels (9-16) are ~45 times higher compared to the channels on the main board (1-8).  This does not happen when I am streaming the data wirelessly to the computer (i.e. both the GUI and saved data file have the correct amplitudes).  I received my board a couple months ago, so it should be running the latest firmware.  Does anyone else have this problem?

Comments

  • biomurphbiomurph Brooklyn, NY
    Can you share a sample of the data that you are having trouble with?
  • armz12armz12
    Sure.  Here is ECG data recorded on channels 1 and 9 with a shared reference electrode using the wireless bluetooth dongle:

    Here is a similar recording saved to the SD card:

    In the second file, you'll see that the signal amplitude is about 45x higher on channel 9 compared to channel 1.
  • biomurphbiomurph Brooklyn, NY
    Ok, looks like the SD data converter that is included in the GUI does not convert 16 channel data correctly.
    Thanks for locating this bug!
    It's on our radar now. 

    The code that the GUI SD converter was based on is here

    We will be working out a fix this week.
  • Winslow_StrongWinslow_Strong
    edited May 2016
    @biomurph did you succeed in a fix?  If so, how do we update our 16-channel systems with it?  If not, is it still on the agenda?
  • biomurphbiomurph Brooklyn, NY
    I will update the code on my github in the next day or two as a quick fix. 
  • armz12armz12
    Why was this not fixed in the OpenBCI GUI 2.0 update?
  • wjcroftwjcroft Mount Shasta, CA
    Including @Conor and AJ @pushtheworld. Did Joel's @biomurph fix miss getting into V2 GUI repo?
  • djfletch42djfletch42 USA
    I believe this is the bug I pointed out in another thread. The conversion algorithm for the hex values is not applied to channels 9-16.
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