Random high intensity signals on the electrodes
Hello,
I am trying to record the signals using openBCI V3 32-bit board. During the recording session, I get random high intensity peaks on the voltage readings. This sometimes affects the frequencies also. The message I get is "OpenBCI_ADS1299: apparent sampleIndex jump from Serial data: 70 to 72 (1)" and so on. I get many of these peaks sometimes and sometimes I don't get any. when this happens the red light on the dongle flickers which is otherwise stable solid red. I am just wondering what is causing this. Thanks
Comments
It could be that the radio link (RFduino Nordic bluetooth/gazelle) between the mainboard and dongle is encountering interference from other Bluetooth devices. Can you try operating your equipment in different environments and see if that affects the lost packets you are seeing?
The RFI / EMI interference may also be leaking into the EEG signals you are seeing that are showing noise bursts. AC power lines and wall wart power packs should also be kept at a distance.
Do you see any different behavior with using the gold cups and paste vs your ultracortex?
With the new firmware it's possible to easily change radio channels. That might improve things somewhat, but the fact that you're seeing noise on the EEG indicates a noisy electromagnetic environment. This same microwave range is used by various equipment such as phones and wireless. It is not generally an issue unless you are in an unusual situation.
Have you tried any tests with another laptop or OS? This looks like Linux? It's possible that the FTDI COM port driver or USB hardware could be responsible for some of the packet loss. A test with another laptop and even another OS could eliminate this possibility.
Another thing you can try is reflashing your mainboard and dongle firmware, but I'd first go for the alternate laptop test. Your firmware is generally working, other than the packet loss issues.
The mystery are the noise bursts we're seeing on multiple channels. Are you sure there is no movement artifact or EMG, muscle activity at those points? Still, noise on the channels should not be correlated with packet loss. I'm not understanding why these are happening together.
Mentioning Joel @biomurph here for reference.
Your other thread with the spectrograms seems to be working fine?? What are the circumstances when the noise appears? What is different?
http://openbci.com/forum/index.php?p=/discussion/785/ultracortex-not-seeing-alpha-waves-at-o1-o2
Best,
William
"Do you see any different behavior with using the gold cups and paste vs your ultracortex?"
When you recorded your spectrograms on that other thread, were you also seeing packet losses there as well? How often do the EMG-like noise bursts happen? Your spectrograms covered several minutes with no bursts.
The fact that your figures in this thread show simultaneous noise on almost all the other active channels, could indicate an issue with your reference lead being intermittent or poor connection. Again, the gold cup comparison test might shed some light. I assume you are using the ultracortex with the supplied silver chloride ear clips. When using gold cups, use gold cups at all locations, including ears.
Another factor affecting latency and responsiveness, is the CPU utilization of the laptop. Run your tests with no other apps active, no file transfers or wifi going on simultaneously. Etc.