VRPN

[uahmed]

Hi Lorena,
I am using the CSP scenario to create the stimulations. I am simple creating the right and left stimulations. There is no issue about the VRPN button, I have made it sure. Are you sure that you do not get this problem? Did you verify it using stimulation listener? If it is so, please send me your algorithm... Also, my device is Emotiv EEG headset.

Thanks

[Lorena]

Hi Uahmed,

I don't know how to use the stimulation listener.

Let me see, if you are using the CSP scenario, then you are using a recorded session, or is it an online acquisition? (Is it the CSP trainer scenario or the motor imagery scenario using CSP filter?)

When you say you keep getting the stimulations even when you are neutral, are you referring to the classified states? I am not sure if the classifier is supposed to classify a, so called, "neutral" state, because in that case you would be working with three states and here we are using two states clasifiers. I think this could be an issue.

Tell me what you think about this

Lorena

[uahmed]

Hi Lorena,
I will let you know the use of Stimulation listener. Btw did you test your stimulations online?
I used all the xml files of the CSP scenario, from online acquisiution to the online test.
Thanks

[Lorena]

Hello all!

I see in the classifier processor configuration box that I can set, besides class 1 and class 2 labels, a reject class label. What does this label refer to? Will it work if I use it to OFF the VRPN buttons?

Thanks!

Lorena

[jlegeny]

Hello,

some classification algorithms can generate a result when they can not classify the vector to a particular class. For example if the vector is on the hyperplane of the LDA classifier then no class can be attributed, so it is rejected (this does not seem to be implemented in the openvibe LDA classifier algorithm though).

This stimulation is sent instead of a class, so it is not suitable for control. Best approach is to ignore the Reject stimulations if they are sparse and raise an error if there are too many of them.

Cheers
Jozef

[Lorena]

Thanks Jozef!

From what you tell me, I assume this rejection class label is not reliable to use as a state to turn ON or OFF a VRPN Button.

So, this is what I have to do with VRPN and I don't know what label should I use to OFF the Button: When the classifier detects left or right, must send it to the external application. When the application receives left or right from this classifier, it does some task and stops "seeing" this classifier. Then, at some point, starts "seeing" this classifier's state again until it detects a state and so on.

In order to do this, I don't know if I should use only one button for left and right (one sets the button ON, and the other one sets it OFF, which I don't think would work ); or two buttons, one for left and one for right, but in this case, what should I use to set OFF the buttons?

Thanks for any help here!

Lorena

[jlegeny]

Hi Lorena,

From what you tell me, I assume this rejection class label is not reliable to use as a state to turn ON or OFF a VRPN Button.

No it is not.

So, this is what I have to do with VRPN and I don't know what label should I use to OFF the Button: When the classifier detects left or right, must send it to the external application. When the application receives left or right from this classifier, it does some task and stops "seeing" this classifier. Then, at some point, starts "seeing" this classifier's state again until it detects a state and so on.

VRPN indeed only sends button states if they change.

In order to do this, I don't know if I should use only one button for left and right (one sets the button ON, and the other one sets it OFF, which I don't think would work :?: ); or two buttons, one for left and one for right, but in this case, what should I use to set OFF the buttons?

There are several ways to do this. Either you can use the VRPN Analog instead of the Button. Analog will send negative values for Class1 and positive values for Class2.

You can also use VRPN Button Servers with two "toggle" buttons (one for left, one for right). These buttons have the same ON and OFF stimulations, for every stimulation received they will change a state and send the command to the application.

Cheers
Jozef

[Lorena]

Thanks Jozef!

I will try those options and let you know how they worked.

Lorena

[Lorena]

Hi all,

I am reading the VRPN tutorial http://openvibe.inria.fr/vrpn-tutorial- ... plication/

I want to download the files mentioned there, but the link is not available (at the beggining, whre it says: "All described files are available for download as an archive here". Is there any available link for download?

Thanks!

Lorena

[uahmed]

http://www.cs.unc.edu/Research/vrpn/downloads/

[jlegeny]

@Lorena: I have updated the page, the files are now available as a download.

[Lorena]

Thanks Jozef!

I am sorry I am asnwering so late, I can't post from my personal computer, some IP problem it seems...

Anyway, I saw your answer last week and could download the files

Lorena

[MOD123]

Hey all,

Can you guys provide me with any tips as to how i can set up the VRPN protocol, I'm having problems completing the tutorial on the openvibe website, and I'm not quite sure as to what else needs to be done, to get it running.

[jlegeny]

hello MOD123,

could you be more specific please? Which tutorial did you try (sending data from or to openvibe)? What exactly did not work in your case?

Cheers
Jozef

[MOD123]

Hey Jozef, i apologize for the late reply and for not providing enough information in my previous post, I just noticed silly me. Anyways I want to use the Motor imagery scenario in openvibe and interface it's output with a microcontroller which is will later on control an couple of servo motors, initial plan was to use the button VRPN server to extract the output and send it to the arduino serial port (I'm also exploring the option of using the MATLAB script box to do the same task instead of vrpn, i posted on that in another thread).

I've tried going through this tutorial http://openvibe.inria.fr/vrpn-tutorial- ... plication/ but i didn't manage to get it up and running, i'm not much of a programmer but i have a feeling that i need to build the entire VRPN client/software first, or at least that's what i understood from their website. So my question is, should i do something (install/build prgram) prior to performing the mentioned tutorial??

I hope this clarifies my request, any help is much appreciated . It was really fun and easy working with openvibe but i'm really confused with this vrpn protocol.