Re: Arduino development possibility

Chuck,

Thanks for your input. Sorry about the multiple send. I'm going to stop
using Thunderbird.

It's a little embarrassing. So, apologies to everyone who I just
irrevocably sent several duplicate posts.

You make some good points about the sampling rate for EEG. I forget I'm not
building a logic analyzer here :P

Best,
Aaron
On Apr 12, 2013 12:58 PM, "Charles Z Henry" <[email protected]> wrote:

> 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