Issue with RAW data from Cyton to Matlab through LabStreamingLayer
I'm having problems reading data from the Cyton board in Matlab through the LabStreamingLayer.
I use the LabStreamingLayer to stream data from OpenBCI (v5.0.1) to Matlab (v. 2019a).
My goal is to analyze data in real time in Matlab.
My problem is that the extracted data processed in Matlab is different from the channel data I read in real time in the OpenBCI GUI.
The settings are:
- PGA 24x
- I do not apply Notch and I do not apply filters in the GUI because I need to analyze in Matlab the raw data for post processing
- Input type Normal
- Bias Includes
- SRB2 On
Is there a need for a conversion between the data I read in the GUI and the data recorded in Matlab?
I have read other discussions but have not found a possible solution.
Comments
Matteo, hi.
Some users have occasionally had issues streaming LSL from the OpenBCI_GUI, into Matlab. Currently it is suggested to use the Matlab interface in Brainflow instead.
https://brainflow.readthedocs.io/en/stable/Examples.html#matlab
https://brainflow.readthedocs.io/en/stable/BuildBrainFlow.html#matlab
Regards, William
Thanks wjcroft for the advice.
I tried to use Brainflow libraries, but there is still the discrepancy between RAW data from Cyton board and data passed to Matlab.
Data range from OpenBCI : 0 - 100 microVolt
Data range read in Matlab : 5x10^5 - 6x10^5.
The value are very different between the two dataset, so my first thought was that there was some missing transformations with LabStreamingLayer, but even with Brainflow i still have the same issue.
Has anyone had similar experiences?
If possible, could someone share a Sample of RAW data (EEG) on which to test my code? It's better if there are Eye Blinks.
(.txt / .bdf format).
Thank you very much
Data shown in GUI is pre-filtered. Cyton recordings and output streams are RAW, no filtering. Cyton data includes low frequencies that can reach millivolts range. You must apply your own filtering.
https://openbci.com/forum/index.php?p=/discussion/201/large-millivolt-data-values-fbeeg-full-band-eeg