Re: [Gumstix-users] High speed ADC

[Bill G. <bg...@bi...>]

Dave Hylands wrote:
> Hi,
>
>   
>> I would like to do some signal processing with Gumstick, mainly
>> averaging and filtering. But ATMega128 can only do 76.9ksps, where I
>> would need at least 20Msps (Analogue signal bandwidth is about 5MHz).
>>
>> 20Msps ADC chips are quite cheap and common now, does anyone know of
>> any existing products that can do at least 8bit ADC at 20Msps, or do I
>> have to make my own?
>>     
>
> The only way I can see that you could possibly get close to 20 Msps is
> to have an ADC that sits right on the bus (i.e. a custom connex card).
>
> Even then, I'm highly dubious that you'd actually be able to get
> anywhere close to that kind of throughput, and actually do anything
> with the data.
>   

At those kinds of rates, you'd probably have to put the whole algorithm 
into an FPGA if you wanted to do the filtering, etc. at line speeds.  
Then you'd have to DMA the outputs into a dedicated SRAM.  Once you 
filled that, you'd have to stop the show--- not unlike how a digital 
oscilloscope works.

Yea, highly unlikely a general-purpose CPU could keep up.  Not with any 
architecture I've worked with, anyway.



b.g.

-- 
Bill Gatliff
bg...@bi...