SRB1 button on GUI

P300_MANP300_MAN
edited August 2016 in OpenBCI_GUI
Dear all, 

I set up device like the first and the second picures. Then I showed software setting like the fourth picture. The problem was that I could not see any EEG signal. No Alpha wave. No blink signal. Even though I used notch filter at 50Hz, I saw 50Hz and 25Hz noise (The fifth pic). When I held everything from table (held on my hand), 50Hz decreased . But, I still see 25Hz noise. Then I tried to disconnect SRB(upper one). But I could not see any difference whether I connected SRB or not. Thus, I afraid that all connections might be wrong. And all signal that I showed in picture was only noise. No EEG at all.

regard to electrode positions : Cz for N1P, left mastoid for BIAS, right mastoid for SRB

Could anyone help me, please? T__________T  Thank you in advance.


image

image
image
image
image

Comments

  • chipaudettechipaudette
    edited November 2014
    Hello P300_Man,

    I don't have my hardware with me here, so I can't test your setup until tonight.  Just based on what I see in your pictures (excellent pictures!), I'd suggest:

    1) If have not done so already, turn off the EEG channels that you are not using (so, turn off 2-8)
    2) We always run at a gain of 24x.  So, I'd reconfigure Channel 1 to a gain of 24x

    Finally, instead of trying to start with getting EEG signals from your head, have you tried getting ECG (EKG) signals?  They're bigger and easier to see.  Just put your eeg electrodes on your wrists instead of on your head (put the bias on the same wrist as the SRB)...


    If it works, the heart signals be so big that you will have to zoom out on the Y-axis of the plots in order to see them correctly...press the "Vert Scale" button a few times to zoom out.

    Chip
  • P300_MANP300_MAN
    Hi, Chip

    About gain and turn off. I had already tried.

    About try to measure other biosignal. I had already tried EMG. The signal was railed after I connected Bias line.

    BTW, What's difference between BLE and PC switches on board?

    Thank you for reply


  • P300_MANP300_MAN
    Hi, Chip,

    I got EMG by enable SRB1 from no to yes . What's SRB1 on your GUI ????

     FFT show raw data right?

    Is it not filtered data as show time domain ?

    Thank you
  • P300_MANP300_MAN
    edited November 2014
    Hi Chip,

    I got Alpha wave!!

    It might be better if we can have short introduction about GUI.

    Here, my problem was solved by only selecting SRB1 from no to yes.

    BTW, I found a bug . Every channel is automatically activated whenever I set SRB or others in setting window.
    FYI

    Thank for kindly reply.

  • wjcroftwjcroft Mount Shasta, CA
    P300_MAN writes:

    BTW, What's difference between BLE and PC switches on board?

    Hi P300, 'PC' position is the normal position used with the dongle plugged into your PC or Mac.  'BLE' is Bluetooth Low Energy, which is more used with mobile devices.  BLE runs with less power and lower data rates than when the dongle is used.  I'm sure the hardware has been checked out, but so far I have not heard any reports from those using the BLE mode outside of Joel's testing.

    ---

    re: your SRB1 setting.  What was the default when you first started the program?  Hopefully settings should default to good values.  If that is not the case we should make adjustments.

    William
  • P300_MANP300_MAN
    edited November 2014
    Dear wjcroft ,

    Regarding to your commments,

    I tried BLE, it's fine.

    About SRB1 , default is "no". It's mean nothing on SRB port (I connected to uppper one on board).

    BTW, What's is SRB1 and SRB2?

    Thank you
  • wjcroftwjcroft Mount Shasta, CA
    edited November 2014
    P300 wrote:  I tried BLE, it's fine.

    Do you mean that the Processing GUI is working fine regardless of the switch position?  Or that you verified BLE works by unplugging the dongle and using the laptop's built-in Bluetooth hardware?

    I have not looked at the firmware connected to the PC/BLE switch, but as a "fail safe" feature when the dongle is detected, it may default to dongle mode.  In other words, to really use BLE in low energy mode, requires unplugging the dongle and pairing your laptop Bluetooth with the OpenBCI board. It may also only interrogate this switch on the OpenBCI board power up.

    re: SRB.  Use the search box on the forum and enter "srb".  You'll find many pages of discussion.  For the definition see the TI ADS1299 data sheet.  SRB is an internal bus inside the chip that can act as a reference point for multiple + or - pins.  Using SRB1 as your reference means all the differential minus sensor leads are tied together and act as a common reference for the individual plus leads.

    William

  • chipaudettechipaudette
    edited November 2014
    Regarding SRB1 and SRB2, they are (as William said) connected to different internal buses within the ADS1299 EEG chip.  These buses allow you to route EEG signals in really interesting ways...primarily with regards to what you do for a reference electrode.

    The shortest practical answer to knowing which SRB1 or SRB2 to use is:

    1) If you choose to use the "P" inputs for each EEG channel, connect your reference electrode to SRB1 (and enable it)
    2) Or, if you use the "N" inputs for each EEG channel, connect your reference electrode to SRB2 (and enable it)

    I believe that the top row of pins are the P inputs, which is what you were connected to, which is why you needed to enable SRB1.  Hopefully, the GUI's defaults are set to be that way.  If they're not, it should get changed.

    Chip
  • P300_MANP300_MAN
    edited November 2014


    Thank you everyone for useful information!, 

    Dear wjcroft, 
    Sorry, I misunderstood. I never try built-in bluetooth. 

    Dear chip, 
    You wrote that P is lower one here. It's better to change to be correct one; otherwise new person might be confused like me. 

    >>>>>>>>>>>>>>>>>>>>
    Chip
    chipaudette October 20 in Hardware

    Getting Started: Confused about SRB and N1P pins
    Great questions. The documentation is still being worked on, so hopefully it can be clarified moving forward.

    Which pins to use is entirely dependent upon the software running on the OpenBCI board. As of right now (but it could change at any point), one use use the "N" inputs (1N, 2N, etc) along with SRB2 as the reference. In terms of the double row of pins, these would all be the upper pins. 

    The lower pins are all of the "P" inputs along with SRB1.

    Again, this could be easily changed via the open source software on the OpenBCI board. So, keep an eye out for updated documentation!

    Chip
    chipaudette October 20 in Hardware
    >>>>>>>>>>>>>>>>
  • chipaudettechipaudette
    Thanks for finding my error!  I'm so sorry for any confusion!

    I went back and edited the post that you referenced.
  • biomurphbiomurph Brooklyn, NY
    Hi,
    Some clarification:

    The SRB1 pin will connect to ALL of the N inputs when you select it in the GUI. That's how the internal MUXer is setup. All or nuthin.
    When SRB1 is connected, the N pin is disconnected from the inputs. Putting a signal on the N input when SRB1 is connected will not have effect.

    The SRB2 pin will connect to ONLY the P input that you select in the GUI. SRB2 is more versitile that way.
    When a give channel's SRB2 switch is closed (connected to the SRB2 pin) the P pin is STILL CONNECTED to the input. Putting a signal on the P input when SRB2 is connected will have an effect.

    I laid out the pins so that the SRB1 pin is on the same side as the P intputs, and the SRB2 pin is on the same side as the N inputs.

    Our documentation is catching up with you! Thanks for your patience
Sign In or Register to comment.

© Vanilla Keystone Theme 2026