OpenBCI triggers with RPi [resolved]
I am facing some issues in interfacing my Raspberry Pi 400 with my OpenBCI. The Raspberry Pi is powered on by means of a 5V, 3A adaptor from a wall socket.
I have created an experiment on my Raspberry Pi to which I have synchronized three GPIOs as output. I need these triggers to observe the response to the stimulus I am providing. These are working fine, as I have tested them with the experiment, first with LEDs and then with the OpenBCI itself.
However, there are some issues I am facing with the interface between the two systems:
1.) Firstly, when I connect the ground of the Raspberry Pi 400 to the ground of the OpenBCI, the LED of the OpenBCI switches off and the system powers down. There have been a couple of times this has not happened and I was able to read the Digital pins on the OpenBCI GUI. However, more than 90% of the time, the OpenBCI powers down when I connect the grounds of the two. Both GPIOs run at the same voltage of 3v3.
2.) Whenever I connected any pin from the Raspberry Pi 400 to the OpenBCI, be it a GND or a GPIO, the EEG waveforms immediately stop giving any meaningful data. The channels go from 'Not Railed' to 'Railed' and the signal I see is 100% noise.
Like I said in point 1, there have been a couple of occasions that the OpenBCI has not powered off when I made a connection between RPi and OpenBCI. During one of these occasions, I have tested the triggers along with the experiment on the OpenBCI GUI using the ‘Digital read’ option (without making the connections for the EEG acquisition) and the triggers worked fine. I have taken a video of this. Similarly, when the triggers are not connected, the EEG acquisition is happening.
Is there any suggestions or possible resolutions you could offer me for this problem, as I have tried everything at my disposal including a resistor divider the circuit between the two grounds.