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Others => Biofeedback - EEG, ECG, EKG => Topic started by: Genei180 on June 21, 2021, 12:08:47 pm

Title: EEG Bitvalue to Voltage Conversion?
Post by: Genei180 on June 21, 2021, 12:08:47 pm
Hello there,

we are a group of people that would like to develop an Open Source Machine Learning Algorithm to classify Sleep Stage Algorithms automatically.

In Order to Train it Correctly, we need to be very strict with classifying it.
Therefore, we need to know the Voltage Representation of the Bit Signal.

We found out so far that the Bit Value Ranges from 0 to 1023, and the Communication Protocol can be found here:
http://openeeg.sourceforge.net/doc/modeeg/firmware/modeeg-p2.c
But personally, I can't find the Conversion in it.

Another Forum Post just assumes 5V:
https://www.olimex.com/forum/index.php?topic=7473.0
It is (in my understanding) at least kind of correct, as it is probably the signal which is scaled to be Put into the Atmel Micro Controller.

But in the Schematic shown here, Page 30:
https://www.olimex.com/Products/EEG/OpenEEG/EEG-SMT/resources/EEG-SMT.pdf
There is a lot of (probably Amplifying) Circuit in front of it.
In there it states:
"voltage divider 1:20000
5Vp-p +/-10% => 250┬ÁVp-p +/-10%"

Does this mean Bitvalue*(5/1023*20000) would be the Formula to go on with?

(Forgive me if there is something wrong with the Above, as I am not very Experienced with Electronics)
Thank you for your Help!
Title: Re: EEG Bitvalue to Voltage Conversion?
Post by: LubOlimex on June 22, 2021, 08:15:15 am
Please check the FAQ section at the bottom of the product page:

https://www.olimex.com/Products/EEG/OpenEEG/EEG-SMT/open-source-hardware
Title: Re: EEG Bitvalue to Voltage Conversion?
Post by: Genei180 on June 26, 2021, 08:19:57 pm
Thank you, Sir, for your very fast Response.

I kind of want to apologize for how easy that should have been found.

But in my defense, the Open EEG Faq: http://openeeg.sourceforge.net/doc/faq.html
does not contain it.

Nonetheless, thank you for your Time and your Impressive Reputation in the Forum.