Multiple Cyton's Simultaneously: (Packet Loss, Pairing, Signal Dropouts)
jean_diddy
France
Hello OpenBCI team,
I am currently working with two Cyton systems and am experiencing persistent connectivity and packet loss issues when using them simultaneously. I would appreciate your guidance.
Setup
Hardware
- 1 × Cyton + Daisy board for EEG
- 1 × Cyton board for ECG
- Subject: Same person for EEG and ECG simultaneously
- Computers: Two separate Windows 10 computers (one per Cyton)
- Software: OpenBCI GUI with FTDI drivers installed
Radio configuration
- Each Cyton paired with its own USB dongle
- One system communicating on channel 10, the other on channel 20
Physical setup
- Computers are ~1 m apart, in the same room
- Each Cyton board is <2 m from its corresponding dongle
Electrodes / grounding
- EEG: Gel cap, GND electrode on scalp (Cyton + Daisy)
- ECG: GND electrode placed on the right hip (Cyton)
Power
- Both computers must be connected to mains power (recordings are too long for battery operation)
Issues encountered
Severe packet loss when both devices are connected, especially once electrodes are attached to the body.
- Packet loss increases significantly compared to when boards are not connected to the subject.
- Packet loss also appears when pressing the PROG button to generate a trigger (following this guide:
https://docs.openbci.com/Cyton/CytonExternal/).
Occasional inability to start recording, even though sessions appear to start correctly in both OpenBCI GUIs.
- The GUI reports “No signal received for 5 seconds.”
After stopping a recording, it is impossible to start a new one without completely restarting the setup.
- We must close the GUI, reopen it, and redo channel selection and pairing.
Intermittent signal dropouts during recording, with the GUI again reporting “No signal received for 5 seconds,” even though nothing in the setup has changed.
Radio channel pairing issues:
- At one point, one Cyton became stuck on channel 10 and its dongle on channel 20.
- We were unable to re-pair the original Cyton–dongle pair (channel 10).
- We tried auto-scan, unplugging the dongle, powering off the Cyton, closing the GUI, and restarting the entire pairing procedure (with the other Cyton powered off), but without success.
What we have tried / considered
1. Reducing distance between Cyton boards and dongles
- Bringing the boards very close to their dongles (<30 cm) significantly reduces packet loss and makes channel selection easier.
We are considering using a USB extension cable for the dongles, as suggested in this thread:
https://openbci.com/forum/index.php?p=/discussion/3216/packet-loss-with-cyton-mounted-on-head-resolvedHowever, this raises a conceptual question: what is the intended benefit of wireless communication if the board needs to be this close to the dongle to function reliably?
2. Following the official multiple-Cyton procedure
We carefully followed the instructions here:
https://docs.openbci.com/Cyton/CytonRadioChannel/Unfortunately, this does not work reliably. Often we need to repeat the procedure multiple times, sometimes taking more than 20 minutes to get both devices working.
- According to the documentation, it should be possible to run up to 25 Cytons simultaneously. We are struggling to get even two to work consistently.
- Are there specific radio channels that should be preferred or avoided?
3. Clarification about “one pair at a time”
- The documentation states: “This procedure must be done one pair at a time.”
Our understanding is:
- Pair and start a session with the first Cyton and its dongle
- Then pair and start a session with the second Cyton and its dongle
Is this interpretation correct, or is a different sequence recommended?
Thank you very much in advance for your help and insights.
Comments
Hi Jean,
Have you already emailed to customer support? That way a ticket will be assigned and multiple engineering staff will look at your issue. Send to (contact at openbci.com). Include a link in your email to this Forum thread.
I know that in the past, running multiple Cyton's in the same room did work, with the units on different radio channels.
William
One consideration to note with the dongle. If the table or surfaces near the dongle are METALLIC, then this can attenuate and distort the transmitted / received radio signals. This is why the usb extension can help. If you use the extension to position the dongle say drape it over the top of a nearby monitor. Then it is off the table and away from metallic objects.
It is also possible that you are in a lab area with many other competing wireless devices (Bluetooth, wifi, cellular, etc.) Getting the dongle off the table and closer to the mainboards will also help reduce cross-interference.
Regards,
Hi William,
Thank you very much for your quick reply and support.
Following your advice I contacted the customer support. Looking at the Open BCI website I thought the forum was the place to ask for help, sorry.
We experienced these issues with wood tables. However, next week I'll try using the usb extension cable.
Regards,
This Forum is good for networking and finding inspiration from other related projects. But for actual hardware or software failures you are seeing (even when following directions), then getting expert advise from the engineers at customer support will speed your resolution.