research with 20 EEGs simultaneously in 1 room / record to SD card or Wifi?

rkennettrkennett Sydney, Australia
edited October 2018 in Hardware
Hi, 
Planning on using for research with 20 EEGs simultaneously in the one room.

1. Can the Ganglion AND/OR Cyton record the EEG data to the SD card? (preferred option)

2. Could 20 headsets (say using WIFI) all record to a single laptop simultaneously? (least preferred option)

Thanks!

Comments

  • wjcroftwjcroft Mount Shasta, CA
    RKennett, hi.

    I suggest you email to contact at openbci.com and ask this question. Particularly since you may be considering a large purchase. Can you also mention a bit about your research experiment here in this thread on the forum?  Mentioning @openbci.

    ---

    1. Cyton supports the SD card. In the 'normal' case with Cyton, the SD card recording session is started from a laptop, which is connected to the Cyton. The GUI currently just supports one board at a time (see below). However if you have hardware engineers, you could do some relatively small custom firmware modifications to the Cyton firmware, that might allow you to start the SD card recording session directly from the Cyton at power up. I know this was done in the past by another Cyton owner for his research situation (using the early v1 firmware.)

    Ganglion, because of the Simblee processor used, has the issue listed here,


    The SD card is also not listed on the Ganglion specs shown in the OpenBCI Shop, so I don't believe it is being actively promoted / supported.


    ---

    2. I know it was mentioned that the OpenBCI_GUI was possibly considering adding support for recording from multiple boards at once, But I don't see that announced yet. 

    I don't know if the Wifi Shields used with Cyton or Ganglion can support 20 simultaneous boards running in the same room. There may be limitations with wifi signal interference. Best to ask this again in your email. Also mentioning the Wifi Shield firmware developer, AJ @pushtheworld.

    Similarly, if you were not using Wifi, but just the built in Bluetooth Low Energy, there are channel limitations with these interfaces that may not support 20 simultaneous boards.

    ---

    Sorry for hedging the responses here, you really need to check with the lab via email or phone. 

    Regards,

    William

  • HirokiHiroki
    I purchased 2 headsets and 2 cyton boards.
    Can I use them simultaneously in one room?
    If the bluetooth signals interfere with each other, how far should I place them?
  • wjcroftwjcroft Mount Shasta, CA
    @Hiroki, hi.

    Your situation should be no problem. Just set the Cyton's so they are using different radio channel numbers. Record those numbers with a small adhesive tag on your mainboards and dongles.

    The original poster was asking about 20 simultaneous boards (Ganglion or Cyton) operating in the same room, which would have to be verified as workable. For example with Ganglion's you cannot specify a radio channel, so all boards would share the radio spectrum space.

    Regards,

    William

  • HirokiHiroki
    Hi William,

    When I use two Cytons, I could not connect to Cytons from my python program.
    The setting is follows:
    - PC #1 -> bluetooth dongle #1 -> Cython #1
    - PC #2 -> bluetooth dongle #2 -> Cython #2

    There are two identical sets for the experiment.
    When I use OpenBCI_GUI.exe from both PCs at the same time, it seems to work as expected.
    But when I call find_port() in cyton.py from my program, I often return OSError('Cannot find OpenBCI port').

    I investigated the cyton.py, I found that the function 'openbci_id' often returns False.
    The reason is either of the following two: 1. serial.inWaiting() returns 0. 2. serial.read() does not return the version information correctly.

    I think that using the two EEG sets at the same time cause such an interference.

    How can I overcome this problem? I try to use two EEGs at the same time in the same room.
  • wjcroftwjcroft Mount Shasta, CA
    Did you change the two systems, so they are on different channels? 


    It's also possible that adjacent channels, such as 3 and 4 or 11 and 12, might somehow be close enough in radio space to interfere. In that case you can use a wider spacing.

    This could also be an issue with the Python code. Can the two system simultaneously stream using the GUI alone? If so, this is not an issue with the hardware, but with a bug in the Python find_port().
  • HirokiHiroki
    Hi William,

    Maybe the problem is fixed.
    I checked the channels and found both channels are set to 20.
    I changed the one channel to 1 and left the other 20.
    When I run my program on two PCs at the same time, then I got no error!
    Thanks a lot!
  • wjcroftwjcroft Mount Shasta, CA
    Great. That should resolve the issue. For future reference, you could also write the channel numbers on the adhesive tags you have stuck to the mainboards and dongles.
  • Ramon3141Ramon3141
    What about passing the data to a pi-zero? can it send it to an SD on the Pi Zero? Maybe that way you can use a camera too, that you can sync with a time stamp. Trying to find some help for that in particular myself but it might provide help here as well. 
  • wjcroftwjcroft Mount Shasta, CA
    https://openbci.com/forum/index.php?p=/discussion/comment/9433/#Comment_9433
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