Everythinh is okay.
Run openbci hub as administrator... ok
Run openBCI GUI as administrator --ok
Swiching on BLE mode Blue light --ok
Selecting port .COM6--ok
Pressing start session-- cyton board Blue light becomes OFF.
What to do ?
I meant to say .... It was working good after oploading last week.
This week after working good again I had to go through.... Autoscan-Get channe-Status.
I have another question. For which it might be very silly for me it is important. In attached picture, pink is analog tone and green/blue is converted signal . Now, on cyton where should I connect the green/blue signal output pin ? Analog(D11-D13) or D17-D18.
So green and blue represent your digital representation of the two types of triggers? Corresponding to the normal and oddball case? Looking at the scale of your scope, the green and blue do not look like 3.3V logic levels. Can you comment. To connect to Cyton digital read pins, signals should be either 0V or 3.3V with respect to your GND.
You may also want to run the digital outputs through a 100K or 1M resistor to guarantee that very low current runs through the wires. Reducing chances that the trigger signals will unintentionally couple (inductive or capacitive) through to the EEG channels.
I meant to say .... It was working good after oploading last week.
This week after working good again I had to go through.... Autoscan-Get channel-Status.
If you are having to repeatedly use Autoscan to synchronize channels, this is hinting that your dongle is not saving the correct channel number. A way this could happen is that if you did not follow all the steps of the dongle firmware upload. The dongle firmware install requires TWO separate uploads. Due to the way the channel is stored in flash memory on the dongle.
So green and blue represent your digital representation of the two types of triggers? Yes
Corresponding to the normal and oddball case? Yes
You may also want to run the digital outputs through a 100K or 1M : Where should I connect? In series with D17-D18?
Did you answer my question about 3.3V logic level?
Your logic output from the Arduino has two wires: signal and ground. The resistor would be in series with the signal wire. Try 100K first. 1M if you see any traces of noise on your EEG channels. You can also use a shielded cable if noise is present. Shield would be the ground line, with signal as the center conductor.
Correct, this is the same as I have been emphasizing. Your Arduino is outputting a 3.3V logic level. That is what you want for a logic input level on Cyton. The voltage divider idea was when you were connecting to the Cyton PIC32 analog GPIO input pin. You now connect to the PIC32 digital GPIO input pin.
The in-line 100K may still reduce current level so as to reduce any inductive/capacitive interference with the microvolt level EEG channels. (Since all these cables are in proximity.) This 100K is NOT considered a voltage divider. Voltage dividers consist of two resistors across the input signal.
So,
I have connected RA0(Low tone)+100K to D17
RA1(High tone)+100K to D18
Tone ground to cyton Ground.
Should I connect any wire with VDD of cyton board ?
Also while recording signal, the cyton Board is on BLE position what shoyld be the status of led of cyton ? It should be continuously ON ?
I have connected 98 K ohm.
third pic is trigger pulses with eeg . 2nd pic is trigger . first pic is only eeg which is showing high micro volt. Confused. Is it okay ?
You already said that, "Tone ground to Cyton ground". The trigger signals are voltage logic levels, so all you need are the signal and ground wires.
DO NOTE that this simple wiring could be somewhat improved (from a strict safety standpoint) with an opto isolator. If for example you were wanting to have maximum isolation from the electrical system of your Arduino, and that of the Cyton. Less relevant if your Arduino is battery powered. An isolator circuit is shown at the end of this page.
However, earlier sections of the article imply just directly connecting your trigger. Since most users of external trigger are not running experiments in a medical context.
Say there are 6 Low tone and 3 High tone . But not all time D17 and D18 works. Like,
L1 L2 L3 L4 L5 L6 H1 H2 H3....L1 L2 L3 L4 L5 L6 H1 H2 H3....
D D . . D D D . D D D . . D D D D ....
N.B. D meaning digital output 0 to 1 on D17 and D18.
All ADC systems only sample the analog stream at specific point. It's possible that your trigger signals are missing the sample window. Seems important for you to TURN ON the trigger signal somewhat in advance of when the audio starts. Possibly up to 4 milliseconds before (4ms = 1/250).
Your oddball audio should indeed be 'odd', and not appear often at all.
@faheemersh
In this link " https://github.com/OpenBCI/OpenBCI_GUI/issues/313",
you told that "Now, I was able to see visual evoked potentials (VEPs) with external triggering (using D17, VDD, GND digital input pins) from a parallel port on a computer with E-Prime software. "
My question is with digital input on D17, WHAT YOU HAVE CONNECTED with VDD of the cyton board ?
There IS NO Vdd connection required to send an external trigger to the Cyton.
IN FACT, connecting Vdd to Cyton would be dangerous and potentially damage either the Arduino or Cyton. Separate power supplies are not meant to be connected in parallel, because they have separate voltage / current regulation. Such regulation is not designed to be ganged together.
Did you answer my point about the sample times not corresponding to your external trigger ON time?
Correct, your Vdd output was powering the optoisolator power input. @Rafia (I inferred) was suggesting connecting the Cyton Vdd output to his Arduino Vdd output. Which cannot work.
As you can see on the current page, initial sections,
In many cases, when optoisolation is not a primary concern, an external (say battery powered) Arduino can drive the Cyton PIC32 input pin(s) directly. In that case only the Arduino output pin and ground need to be connected.
Since the Cyton is battery powered, there are no "ground loops" possible. The only reason I mentioned the 100K on the logic pin, was to reduce any potential capacitive / inductive coupling to EEG cables. You may not even need that. Just run the GUI and see if your trigger is leaking into an EEG wires.
Comments
The problem is solved. I had to go through.... Autoscan-Get channe-Status
Why this is happening ?
Is it possible that your dongle firmware is not programmed correctly? Did you follow the steps,
https://docs.openbci.com/docs/02Cyton/CytonRadios#uploading-host-firmware-to-the-openbci-dongle
yes.
now working. The problem is solved. I had to go through.... Autoscan-Get channe-Status
You say "Why is this happening?", implying that the Autoscan must be used more than once. Please clarify.
I meant to say .... It was working good after oploading last week.
This week after working good again I had to go through.... Autoscan-Get channe-Status.
I have another question. For which it might be very silly for me it is important. In attached picture, pink is analog tone and green/blue is converted signal . Now, on cyton where should I connect the green/blue signal output pin ? Analog(D11-D13) or D17-D18.
The attached pic
Quote
So green and blue represent your digital representation of the two types of triggers? Corresponding to the normal and oddball case? Looking at the scale of your scope, the green and blue do not look like 3.3V logic levels. Can you comment. To connect to Cyton digital read pins, signals should be either 0V or 3.3V with respect to your GND.
You may also want to run the digital outputs through a 100K or 1M resistor to guarantee that very low current runs through the wires. Reducing chances that the trigger signals will unintentionally couple (inductive or capacitive) through to the EEG channels.
If you are having to repeatedly use Autoscan to synchronize channels, this is hinting that your dongle is not saving the correct channel number. A way this could happen is that if you did not follow all the steps of the dongle firmware upload. The dongle firmware install requires TWO separate uploads. Due to the way the channel is stored in flash memory on the dongle.
So green and blue represent your digital representation of the two types of triggers? Yes
Corresponding to the normal and oddball case? Yes
You may also want to run the digital outputs through a 100K or 1M : Where should I connect? In series with D17-D18?
Did you answer my question about 3.3V logic level?
Your logic output from the Arduino has two wires: signal and ground. The resistor would be in series with the signal wire. Try 100K first. 1M if you see any traces of noise on your EEG channels. You can also use a shielded cable if noise is present. Shield would be the ground line, with signal as the center conductor.
Yes.
I will try with 100K and will let you know.
AGAIN: "Did you answer my question about 3.3V logic level?"
The scope traces don't seem to show logic ON = 3.3V. Logic off = 0V. What are your levels?
my pin output is 3.1 volt to 0 volt.
My Professor is telling me that now I don't need to use voltage divider. What is your comment?
Correct, this is the same as I have been emphasizing. Your Arduino is outputting a 3.3V logic level. That is what you want for a logic input level on Cyton. The voltage divider idea was when you were connecting to the Cyton PIC32 analog GPIO input pin. You now connect to the PIC32 digital GPIO input pin.
The in-line 100K may still reduce current level so as to reduce any inductive/capacitive interference with the microvolt level EEG channels. (Since all these cables are in proximity.) This 100K is NOT considered a voltage divider. Voltage dividers consist of two resistors across the input signal.
So,
I have connected RA0(Low tone)+100K to D17
RA1(High tone)+100K to D18
Tone ground to cyton Ground.
Should I connect any wire with VDD of cyton board ?
Also while recording signal, the cyton Board is on BLE position what shoyld be the status of led of cyton ? It should be continuously ON ?
No, Vdd on Cyton is not relevant in this case.
The switch on the Cyton, does not care which position it is in. BLE or PC. Both operate the same.
Just run your test and setup the Aux data to reflect the pins in digital read mode.
What about Ground connection ?
I have connected 98 K ohm.
third pic is trigger pulses with eeg . 2nd pic is trigger . first pic is only eeg which is showing high micro volt. Confused. Is it okay ?
You already said that, "Tone ground to Cyton ground". The trigger signals are voltage logic levels, so all you need are the signal and ground wires.
DO NOTE that this simple wiring could be somewhat improved (from a strict safety standpoint) with an opto isolator. If for example you were wanting to have maximum isolation from the electrical system of your Arduino, and that of the Cyton. Less relevant if your Arduino is battery powered. An isolator circuit is shown at the end of this page.
https://docs.openbci.com/docs/02Cyton/CytonExternal
However, earlier sections of the article imply just directly connecting your trigger. Since most users of external trigger are not running experiments in a medical context.
Say there are 6 Low tone and 3 High tone . But not all time D17 and D18 works. Like,
L1 L2 L3 L4 L5 L6 H1 H2 H3....L1 L2 L3 L4 L5 L6 H1 H2 H3....
D D . . D D D . D D D . . D D D D ....
N.B. D meaning digital output 0 to 1 on D17 and D18.
All ADC systems only sample the analog stream at specific point. It's possible that your trigger signals are missing the sample window. Seems important for you to TURN ON the trigger signal somewhat in advance of when the audio starts. Possibly up to 4 milliseconds before (4ms = 1/250).
Your oddball audio should indeed be 'odd', and not appear often at all.
@faheemersh
In this link " https://github.com/OpenBCI/OpenBCI_GUI/issues/313",
you told that "Now, I was able to see visual evoked potentials (VEPs) with external triggering (using D17, VDD, GND digital input pins) from a parallel port on a computer with E-Prime software. "
My question is with digital input on D17, WHAT YOU HAVE CONNECTED with VDD of the cyton board ?
There IS NO Vdd connection required to send an external trigger to the Cyton.
IN FACT, connecting Vdd to Cyton would be dangerous and potentially damage either the Arduino or Cyton. Separate power supplies are not meant to be connected in parallel, because they have separate voltage / current regulation. Such regulation is not designed to be ganged together.
Did you answer my point about the sample times not corresponding to your external trigger ON time?
No. I was just asking him.
I will work on your advice. Will let you know.
@wjcroft
Back then, I used the optoisolator setup from the external triggering page on the OpenBCI website. Using the setup shouldn't cause any issue if Vdd is connected, right? If connecting to Vdd is an issue, then this page may not be a good reference to follow, but again, I thought the optoisolator solves the issue of potential damage to the cyton board: https://docs.openbci.com/docs/02Cyton/CytonExternal#optoisolation
@Rafia
In my github, I detailed those connections with the setup I was using:
https://github.com/faheemersh/Senior_Design_Dry_EEG_BCI/tree/Validation#external-triggering-with-openbci
@faheemersh, hi.
Correct, your Vdd output was powering the optoisolator power input. @Rafia (I inferred) was suggesting connecting the Cyton Vdd output to his Arduino Vdd output. Which cannot work.
As you can see on the current page, initial sections,
https://docs.openbci.com/docs/02Cyton/CytonExternal
In many cases, when optoisolation is not a primary concern, an external (say battery powered) Arduino can drive the Cyton PIC32 input pin(s) directly. In that case only the Arduino output pin and ground need to be connected.
Regards,
One of my friend advising me to add large value resistor between the pin and GND.
What do u say? Is it safe?
Since the Cyton is battery powered, there are no "ground loops" possible. The only reason I mentioned the 100K on the logic pin, was to reduce any potential capacitive / inductive coupling to EEG cables. You may not even need that. Just run the GUI and see if your trigger is leaking into an EEG wires.
Hi,
Now the problem is solved. I had to increse the PW of my external trigger. At previous, it was around 300 ms . Now around 900 ms.