TTL triggering
Hi,
I am new to OpenBCI, and so far I am happy about the recently purchased Cyton board.
I plan to use the Cyton board in a psychological experiment. To ensure precise timing of events on the EEG, the OpenBCI system needs to receive a TTL trigger from a stimulus presentation computer (triggered inside the E-Prime software). I think the use of a USB to serial UART cable, as well as some wiring and firmware changes may do the trick, but I am not sure.
Is there any practical advice as to what I can do to set up the communication? @wjcroft @retiutut @evaesteban
Many thanks!
Best,
Michael
Comments
Michael, hi.
See the optoisolator diagram.
https://docs.openbci.com/Cyton/CytonExternal/#optoisolation
The external trigger data is then received in the three 'Aux' channels of Cyton. These replace the Accelerometer when the Cyton is placed into 'digital' or 'analog' read mode.
https://docs.openbci.com/Cyton/CytonExternal/#programmatically-setting-board-mode
Regards, William
It's also a good idea to keep your 5V TTL signal lines, AWAY from EEG electrode cables. Possibly even shielded. Because 5V square wave pulses are ~ million times stronger than microvolt EEG signals. And can bleed in via inductive or capacitive coupling.