Re: Arduino development possibility

Hi Aaron

I also wanted to talk about things that aren't easy, for a few minutes here
:)

I have been looking at FPGA programming for building a open source sound
card architecture that scales to large numbers of channels ( a similar
problem to recording EEG signals).

At first, I was thinking of using the FPGA to talk to ADC's over SPI or
I2C... However, this approach has a definite cost (and intellectual
property) drawback.  I now think that a better idea is to build sigma-delta
ADC arrays on an FPGA itself.

At very low sampling frequencies (as in EEG recording), you can build a
1st-order or 2nd-order converter with low-enough noise.
THAT kind of hardware project could get you to 192 channels without being
prohibitively expensive.

I'm just getting started reading for the adc designs (and who knows if I'll
ever get it off the ground), but I'd be glad to have your thoughts on it.

Chuck


On Fri, Apr 12, 2013 at 7:59 AM, Aaron Silber <[email protected]> wrote:

>  Welcome to the OpenEEG list. I apologize that I cannot read or pronounce
> your name, as I only speak English.
>
> You're very right when you acknowledge that it won't be easy :) The
> "typical" Arduino (ATMega8/168/322) only has less than 30 total GPIO pins,
> closer to 20. Processing the 4 or so channels we have is difficult enough
> to perform analog/digital conversions and all the serial communications in
> real time. An ATMega168 is only rated to 20MHz, after all (and often gets
> run at 16MHz).
>
> 192 electrodes! That's a whole lot of electrodes, a whole lot of paste,
> and a whole lot of data. I guess if you need that many then you really need
> that many.
>
> So, I think that working on modifying the modularEEG design to accommodate
> that many inputs would need in some regards a complete reworking. There are
> some good parts of the project such as the way DRL and active probes are
> handled that can be used to your advantage. They have already been designed
> and tweaked, so I would imagine it better to not "reinvent the wheel" there.
>
> A faster processor and enough I/O are two requirements. You will not
> necessarily need 192 GPIO as this can be very expensive to find in a
> microcontroller - utilizing discrete circuitry such as dedicated ADC's and
> multiplexers can reduce this number greatly. Atmel, manufacturer of the
> ATMega line, also makes other processors all the way up through FPGA's. The
> ARM architecture is also a possible route. The Cortex series can achieve
> good speeds and versatility at good prices. Think of mobile devices and how
> much power they can get with relatively little expense.
>
> I wish you good luck! Keep in touch.
>
> -Aaron
>
>
> On 04/12/2013 07:20 AM, ΓΛΥΚΑΣ, ΣΩΤΗΡΙΟΣ wrote:
>
> Hello to everyone and I hope I'm in the right place.
> I'm thinking of expanding the current openEEG capabilities to be able to
> be used for lab purposes, professional use etc. for a project at my
> university. I was thinking of 192 electrodes with enough analog arduino
> inputs and a usb or serial exit to PC with all the data needed by the
> currently existing openEEG software.
> I know it won't be easy but I'm willing to study, work and learn.
> I'll probably have to build my own arduino board, I don't think that any
> with the specifications I need already exists.
> This is where you guys come in, do you think it's possible with something
> like this or is it not powerful enough? Should I use something else?
> Also, currently there are analog and digital boards, do you think it would
> be easier if I used 2 arduinos? One for processing the analog and one for
> the digital signals?
> Thank you in advance.
>
>
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Precog is a next-generation analytics platform capable of advanced
analytics on semi-structured data. The platform includes APIs for building
apps and a phenomenal toolset for data science. Developers can use
our toolset for easy data analysis & visualization. Get a free account!
http://www2.precog.com/precogplatform/slashdotnewsletter