OpenBCI_GUI Hardware Settings Instructions

HanNguyenHanNguyen Vancouver
in OpenBCI_GUI
I am quite confused of the Hardware Settings of OpenBCI_GUI. Where may I find the detailed instructions for it?
I have found information about the input types in the ADS1299 datasheet, but still confused of when to use each of them:
"000 : Normal electrode input
001 : Input shorted (for offset or noise measurements)
010 : Used in conjunction with BIAS_MEAS bit for BIAS
measurements.
011 : MVDD for supply measurement
100 : Temperature sensor
101 : Test signal
110 : BIAS_DRP (positive electrode is the driver)
111 : BIAS_DRN (negative electrode is the driver)"
When the screen shows "Don't include" for BIAS, does it mean the measured EEG does not consider the BIAS electrode?
Also, I would like to see the voltage difference between each channel and the common ground (SRB1/SRB2?) How should I set up the electrodes (connect to which pins) and the Hardware Settings in OpenBCI_GUI?
Thanks a lot,
Han

Comments

  • wjcroftwjcroft Mount Shasta, CA
    Han, hello.

    Did you try all the steps of the Cyton tutorial?


    They cover the common cases of EEG, ECG, EMG. And how to disconnect the SRB* (reference) bus on those channels you are wanting to use differentially. In the case of ECG, it is also disconnected from the Bias generation, because otherwise the ECG is so strong it pollutes the EEG.

    The default channel settings need no adjustment for 8 channel EEG. In that case the common reference is on SRB2. All channels use the pins closest to the board surface.

    Regards,

    William

  • HanNguyenHanNguyen Vancouver
    Thanks, William. I have read that page, but I couldn't find when to use each input type. The example there use "Normal" only. When should I use the other ones such as BIAS_DRP and BIAS_DRN?
  • wjcroftwjcroft Mount Shasta, CA
    edited June 2019
    What is your goal? What kind of signals, channels, references, etc. are you using in your experiment? The GUI channel settings page just allows you to change the default settings if desired. Such as per channel scale factor, whether Bias is included, and if the channel is included in the SRB1 or SRB2 reference bus.
  • HanNguyenHanNguyen Vancouver
    I just want to find voltage difference between each electrode and the common ground one (SRB1 or SRB2?). Does including BIAS help reduce noise? So should I always use "Normal" as input type?
  • wjcroftwjcroft Mount Shasta, CA
    edited June 2019
    Han, thanks.

    The default settings are fine for almost all EEG applications. You don't need to adjust any of them. 'Normal' input type is the default. SRB2 is your default reference. It is on the pin closest to the board. All the channel pins are closest to the board. Bias is the same as Ground in other EEG systems. The tutorial explains when it is turned off on the ECG channel. Yes, Bias injects a small counter common mode noise offset to reduce noise.

    Please consider going through the steps of the Cyton tutorial. It explains the rare situations when the Bias or SRB2 is turned off. (When doing simultaneous EEG and ECG/EMG.)

    William

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