cEEGrid missing second half of channels (9–16)
Hi everyone,
I’m experiencing an issue using a cEEGrid 16-channel system on a Windows laptop. Initially, all 16 channels work correctly. However, after a couple of minutes, the second half of the channels (channels 9–16) stop streaming and no longer appear.
I tried turning the device off and back on, but channels 9–16 remain missing.
Interestingly, when I test the same setup on a MacBook (on different days), all 16 channels work fine, even after more than 1 hour of continuous streaming.
Has anyone experienced a similar issue? Could this be related to the Windows OS, or possibly the use of a USB extension cable on the Windows laptop?
I plan to use this cEEGrid together with fNIRS, so I want to make sure everything is working properly before running real participants.
Thank you in advance for any suggestions or insights.
Comments
Hendrik, hi.
I'm reaching out to Michael Knierim, the cEEGrid developer, to see if he might have any comments. Hopefully he will post on a followup comment here.
When you say "the second half of the channels (channels 9–16) stop streaming and no longer appear." Can you clarify, perhaps with a screen shot? You mean that 9-16 just flatline with 0uV, or does something odd happen on the Time Series widget graph?
It would not be the USB extension cable. My initial impression is that this could somehow be related to a loose connector somewhere in the pathway between the skin and the Cyton input pin. Because 9-16 is on a different set of cables / converter, than 1-8.
William
Hi William, thanks for your response.
I don’t have a screenshot, but yes—this means that channels 9–16 (right ear) are showing flat/railed signals (0 µV). Also, the file size is only about half of a successful recording. For example, a successful 16-channel recording is around 20 MB, whereas a session with the missing second-half channels is only about 10 MB. This suggests that nothing is being recorded for channels 9–16.
To clarify, your recording is not using the sdcard, correct? It is only the text file CSV recording produced by the GUI. The size difference may be explained if the sample values are all 0.0 instead of the longer values that have many more digits.
Have you emailed to (contact at openbci.com) to open a customer support ticket? It is remotely possible that this is some kind of glitch in the OS or GUI, but that seems unlikely.
Michael has offered to take a look at this Forum thread to see if he has any insights. Mentioning his Forum ID: @MKnierim .
William
Yes, I am not using an SD card. Instead, I am using LabRecorder to stream data from OpenBCI along with the stimulus presentation from PsychoPy. I tried again today on my MacBook, and it still works fine. I may need to test it again in the lab using a Windows laptop.
Thanks—I will also contact their support to get their opinion.
Hmm, so another possible failure point is with the LSL LabStreamingLayer setup or the GUI's implementation of the out-streaming of LSL packets. Do you absolutely need the LSL? Can you try a Windows test without LSL?
https://docs.openbci.com/Software/CompatibleThirdPartySoftware/LSL/
Yes, I need LSL. I need the stimulus information from PsychoPy.
I do not think this is the issue, as I am still recording data using the OpenBCI GUI (CSV and TXT files).
The missing second-half channels appear directly in the OpenBCI GUI. LabRecorder is only recording in the background.
Thanks for the link, I already followed the instruction from the link as well.
OK, right. The GUI Time Series widget is showing the flat lines for 9-16, so the signals are not reaching the Daisy board.
But... for ALL the signals to be affected at once, this seems to point to some mechanical (possibly intermittent) failure issue in the SRB reference lead connection to the Daisy board. In the original Daisy configuration (non-cEEGrid), there is a Y-cable between the SRB2 pin on the mainboard and the SRB2 pin on the Daisy. I would wiggle, examine this Y-cable to see if may be possibly intermittent.
Hi Hendrik,
thanks for all the details so far! Generally (regardless of Windows or Mac) I have seen the issue of "Chan9-16" are all flat a few times now - it also happened just a few weeks ago in our lab. My first guess then was (and usually is, when this happens) that there is a weak(ened) connection between the Daisy and the Cyton board. In our case, the Y-split cable for SRB2 was poorly connecting the Cyton and Daisy. So, could you please double-check, if the REF electrode (the one connected to SRB2) is securely attached on both the bottom row Cyton and Daisy pins? Could you share a picture of that? Of course, that is assuming that the channels 9-16 are all supposed to be connected to the Daisy module...
Best regards
Michael
Thanks Michael for your response.
I am attaching a picture of my cEEGrid.
Now I am a bit confused. I followed the description on the website stating that the left-ear L6 should be connected to the SRB on the Cyton board, but not to the SRB on the Daisy shield. However, based on your comments, it seems that I need to connect the Y-split from the SRB on the Cyton board to the SRB on the Daisy shield as well.
I have tried this multiple times on my personal Mac, and all 16 channels are still recording correctly. I will keep this in mind, and if the second half of the channels goes missing again, I will pay close attention to the SRB connection on the Y-cable.
Dear Hendrik,
ok yeah that seems to be the culprit then - I see that there might be some potential for confusion. Yes, the L6 is recommended as the REF electrode for all 16 cEEGrid chans. But, to make that work correctly, the L6 pin should be connected to the Y-split cable, which in turn should be connected to SRB2 on the Cyton AND the Daisy - so that both boards are connected to this reference channel. That should do the trick then!