SD card Sampling rate and OpenBCI GUI v4.2.0

ShyamalShyamal Canada

I'm using Cyton Daisy with SD card for collecting EEG data. The sampling rate mentioned on website is 250hz, however, my data is being sampled at 256hz, as shown in this images:

Is it okay to have this minor difference?

Also, in order to convert the hex valued .txt file stored on sd card, I'm using OpenBCI GUI v4.2.0 which has inbuilt option to convert the sd card file. Is it a good way to convert sd card files for now?



  • Ignore the data of EEG channels in the images.

  • wjcroftwjcroft Mount Shasta, CA

    No, the column you are looking at is a "packet counter" one byte value that cycles through 0 to 255 and repeats. Not relation to the sample rate. The sample rate is 250.x Hz plus or minus a few tenths of a Hz.

  • wjcroftwjcroft Mount Shasta, CA

    I believe Richard @retiutut knows if an external hex conversion program is in the works.

  • Understood, Thank you @wjcroft. Waiting for Richard's @retiutut comment on hex conversion using GUI v4.2.0.

  • retiututretiutut Louisiana, USA

    Yes, a new Hex conversion tool is in scheduled for the very near future. Tasks for the public repos and GUI have just been re-prioritized for early 2023.

  • Thanks Richard @retiutut for the update, however, just wanted to confirm that is it safe for us to use OpenBCI GUI v4.2.0 for now for hex conversion until the new GUI release?

  • retiututretiutut Louisiana, USA

    @Shyamal Where are you trying to use the SD card files primarily? GUI v5.1.0 can play back these files just fine as it converts them in the background.

  • I'm using it to convert it to .csv file and then using mne python to again convert it into .eeg file. The .csv file will enable me to convert the data into numpy arrays for machine learning applications and .eeg file is just for standardizing the dataset.

  • retiututretiutut Louisiana, USA

    In your case, you can probably continue to use 4.2.0 to convert the files. I'd like to also distribute a Python script to everyone that accomplishes this much.

  • That would be great! Again Thanks Richard @retiutut.

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