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OpenBCI
WiFi shield packet loss causes cyclical noise spikes
See attached screenshots. You can see there is a spike of noise once every second or so. I'm switching back and forth between Dongle and WiFi shield, and it only appears when using WiFi, so it doesn't seem to be an environmental effect.
I'm using 1000Hz and 10ms latency.
Now this is only happening every once and a while for me. I'm not sure what is the root cause. It could be my hardware. I'm interested to see if anyone else experiences something similar using the WiFi Shield.
Are these regularly spaced? Could you try updating your firmware? Maybe something got botched the first time?
Hi guys, was there any progress on this?
I'm also experiencing cyclical noise spikes, which vary between 1-4hz, and only appear occasionally. The occurance of these cyclical spikes seems loosely correlated with resetting the system through the OpenBCI GUI.
I'm not using a WiFi shield, just the regular cyton EEG sensing board. It had been working well up until tonight.
I was playing around with the BIAS and SRB pins before I saw this behaviour. Any ideas?
Hi! There has been a lot of progress on this re: Cyton with WiFi shield. However this is not an issue we normally see with the Cyton over serial. Could you upload a screen shot of your spikes here?
Hi AJ, thanks for the quick reply!
I actually just left work so cant take any more screenshots until I get in tomorrow morning (different time zone here in Aus), however I did take this photo showing what happens after repeatedly connecting-disconnecting the system through the OpenBCI GUI. For some reason, the frequency of the pulses get faster each time I disconnect-reconnect, and after 6-7 iterations this is what i end up with.
Its a strange waveform thats distinctly different from random noise. While showing this waveform im unable to sense any EEG data.
Have you seen this before? Apologies if Ive gone too off track with this issue - this is really confusing me haha. Will upload pulse screenshots in the morning.
That looks almost like a test signal, hmm is this issue still happening?
I am experiencing this issue also when using the wifi shield with 8 channels and using two separate batteries (4xAA and 3.7v 500mah).
The WiFi shield firmware is v2.0.5 . Updated the Cyton firmware this morning and still having same problem:
I've mostly been using TCP. I did swap out the WiFi shield for a Daisy header and was able to see proper EEG over BLE using the dongle. I'll try UDP and UDPx3 later today or tomorrow.
No doubt in my mind this is 100% due to using WiFi! This can happen on some routers I’ve seen, it should magically disappear with UDP. Probably won’t happen with TCP over WiFi direct too.
To document: I'm using a current generation Airport Extreme mounted high on the wall. The LOS distance from the Airport to the WiFi shield was about 5 feet.
Had to put my iPhone in airplane mode to have uninterrupted upload for the Cyton firmware via Arduino IDE. Left it in airplane mode during these tests.
This issue is still happening over UDP, rendering the WiFi shield unusable. Was not able to find the shield using WiFi direct in the GUI.
I erased the network credentials again, got 10 blinks in 2 seconds on boot, and connected to the Wifi shield. The GUI still only finds this:
@aj-ptw What settings (hardware and software, apart from up-to-date firmware) would you recommend to resolve this issue? I was looking forward to the increased resolution over WiFi, but I get worried every time I have to change the hardware just to see if the WiFi shield works.
@retiutut could you try on a different router? If not, maybe we can do a call and I show you how WiFi direct works. Skype me at pushtheworld_aj
I think I have to try and update the Cyton firmware again. I'm having serious issues over BLE also. Here we have a series of eye blinks followed by rest and then a spike across all channels.....
Hey @retiutut ! I have just finished a new gui version that will allow you to use the wifi direct for sure.
I have identified the cause of the problem using the Processing version. I see packet loss correlations with these visible spikes when using an Airport Extreme. I was able to finally connect via wifi direct using a newer Mac Mini and I still see regular spikes when streaming. Here is a screenshot that documents this issue:
Hi guys, was there any progress on this? I have same issue with wifi shield but not with USB dongle.
I have same issue with wifi shield but not with USB dongle.>> So it is likely that you have electrical/ magnetical interference from the shield. You see also in your example that despite you have 60hz notch on there is huge 60Hz in the spectrum. This tells you what these signals are. Do you use AC adapter or battery. The latter is important! Also for safety reasons.
You can place a grounded copper foil between shield and cyton or play around with electrode cables location.
Another idea to figure out the cause is to short the inputs. Open inputs are very sensitive. For example I 3D printed a self-designed housing with ABS and noticed spikes appearing randomly in the time series. Then I noticed that just rubbing the outside of the box caused charging the plastic and hence lead to spikes. Counteraction was to paint inner side of housing with copper laquer used for EMI https://www.conrad.at/de/abschirmlack-crc-kontakt-chemie-emv-35-77509-aa-200-ml-813893.html and to connect the shield to ground. This also improved significantly mains interference.
NOTE: Do not paint the housing close by the antenna !!
