Re: [Openeeg-list] OpenEEG Questions

[Damián F. <nog...@gm...>]

I am not, really... :D
Can you please define "leads"? Do you mean channels?
And what challenges?

OpenEEG is in default built as bipolar EEG. That means for each channel you
need to connect two electrodes. The output is difference of voltage between
those two electrodes. But even with two electrodes you won't need to make
two amplfication circuits. The difference of voltages is processed in the
instrumentation amplifier (first amplifier) and then the one difference
signal is amplified further, so it can be reliably converted to digital
data. So you will need an amplification circuit (cascade) for each channel
(2 electrodes).
OpenEEG with v2 protocol and baud rate 115200 can support up to 6 channels,
although ATmega16 can support 8. If there is need for more channels, you
would have to rewrite the firmware and change the baud rate. But with that
you would lose compatibility with software supporting OpenEEG (like
BrainBay).
I simply chose not to face those challenges and I stuck to the
specifications concerning OpenEEG compatibility. I use olimex v2 protocol
firmware with ATmega16L.



On Sun, Sep 20, 2020, 23:18 Steve Sterling <acu...@gm...> wrote:

> You're really knowledgable about this Damian!  How do you work around the
> challenges with multiple leads, will each lead require it's own circuit?
>
> Thanks,
> Steve
>
> On Sun, Sep 20, 2020, 1:17 PM Damián Filo <nog...@gm...> wrote:
>
>> I am sorry for the spam, but in my previous e-mail I said: "any of those
>> changes you proposed are possible" - that is false. One change you
>> mentioned was to feed raw data onto GPIO pins of RPi. That will not work,
>> because what you need to do with the signal is to convert it from analog to
>> digital data through ADC and RPi doesn't have an ADCs. You can avoid using
>> ATmega microcontrollers, but you still would have to use some external chip
>> with ADC functions. And then you would have to program your own firmware
>> and protocol, so you can use the data in applications running on RPi.
>> Though what you can do with RPi is to feed the data directly from ATmega
>> through native UART interface on RPi without the need for USB-UART chip.
>> But about that, I am not really sure about the signalling voltage mismatch
>> 5V/3.3V. So it is still preferred to use a USB interface with UART bridge
>> like CP2102.
>>
>> S pozdravom,
>> Damián Filo
>>
>>
>> so 5. 9. 2020 o 21:49 Yonah Elorza <yo...@gm...> napísal(a):
>>
>>> Hello!
>>>
>>> I'm a computer engineer interested in making some modifications to the
>>> OpenEEG circuit, and had a few questions, if anyone is available to answer
>>> them. I've read through all the documentation on the website, and have
>>> worked with the OpenEEG platform for a few years now, and wanted to see if
>>> the following was possible:
>>>
>>> -Designing better noise cancelling to reduce commons noise, as well as
>>> noise between electrodes.
>>> -Integrating an FPGA into the design which acts as a hardware Fast
>>> Fourier Transform
>>> -Making the circuit modular enough that you can stack multiple together
>>> to have 4, 8, 16, etc. electrodes reading at the same time.
>>> -Long term: modifying the design of the circuit to work without the AT
>>> processor, instead having hardware control from the GPIO of a Raspberry Pi,
>>> and all data being fed raw to either the GPIO or USB interface of the Pi.
>>>
>>> If anyone has reasons this wouldn't be possible, or if you have
>>> suggestions for any of these changes, please let me know. I absolutely love
>>> this project, and would love to be able to contribute my own work to it.
>>>
>>> --
>>> Best Regards,
>>> Yonah Elorza
>>> Columbia School of Engineering | Class of 2018
>>> Computer Engineering
>>> Tel: ( <%28786%29%20205%20-%204304>305)-542-1735
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