Re: microcontroller advice? how to go about this...
From: Ulf Samuelsson (ulf_at_atmel.nospam.com)
Date: 05/10/04
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Date: Mon, 10 May 2004 19:22:48 +0200
Do you need to build many such devices or is it one off.
If it is a one off, then I 'd go with multiple 12 bit ADCs with an SPI
interface.
Then you connect that to a nice high end CPU with Ethernet. (AT91RM9200 :-)
More expensive than the multiple 8 bitters, but probably higher quality on
the ADC.
USB is not so easy to work with.
TCP/IP is supported in a much better way by the industry.
-- Best Regards, Ulf Samuelsson ulf@a-t-m-e-l.com This is a personal view which may or may not be share by my Employer Atmel Nordic AB "Fred Trinkoff" <fct2@cornell.edu> skrev i meddelandet news:fct2-27589E.02405010052004@newsstand.cit.cornell.edu... > Hey everyone, > > I have a challenging project ahead for a large university and I was > wondering if someone could give some advice on what the best way to go > about this is... > > Essentially what we need done is to read in about 32 ->64 (or more, > eventually, if possible) analog samples every millisecond - preferably > about 12-bit accuracy or better (my advisor said that, I'm not convinced > that 8 isn't fine too, but we'll see). Storing about 1/4 -> 1/2 a > second's worth of data to run algorithms on and look for patterns. Also, > it'd be nice (but not vital) to be able to transmit all that information > to a computer, which would probably require USB (alternately, we could > probably hook up the connection to some hardware in parallel, so the > data doesn't *need* to be fed through the controller). > > Issue #1- > So, 64 analog samples/millisec - coming from 64 different probes - any > advice on some kind of an 'analog multiplexer'? Can such a mux switch > fast enough to support that kind of data reading? I see ADCs tend to get > to 100-200 ksbs, so that part should be alright. What's the best way to > go about being able to read all this data from different sources? > > Issue #2- > Second, enough memory to hold 250 or 500 sets of data, that's also fast > enough to keep up with this rate of reading/writing. Worst case: 16 bits > -> 2 bytes * 64 samples * 500 ms = 64 k of RAM just for this. Can get > down to 32 K or sure with 1 byte data, or 250 ms, or some reasonable > combination. > > Issue #3- > Preferable, but optional: To transmit all that data to a comp we're > talking 128 K/sec = 1 mbps - so we'd need USB, probably USB 2.0 - what > does USB 1.1 get realistically? > > Issue #4- > Would I need a separate interface through the normal I/O pins be able to > send a signal back to those original location (to stimulate the tissue > there). Is there any other way to do that? > > So... > Any advice on a chip that can handle all of that? Not to mention that it > still needs to be fast enough to do computation on top of it, with all > the data in memory. Would it be wise to have dedicated ADC chip that > I've seen to do the gathering and a separate ucontroller for the rest? > Cost is a minimal concern as this is for a large research university. > > Thanks guys! > > -Fred
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