Re: Searching SBC/DSP board/microcontroller; 4ADC/1kHz/USB Host

First of all, sorry for not replying for so long. I was having trouble
logging into the website, and it took a little while to get it sorted out
with the webmaster.

I had meant to reply the day you guys posted, but as I said couldn't.
I've been able to find a solution or two in the meantime:

APF27 dev_light board
http://armadeus.com/english/products-development_boards-apf27_dev.html

TS-7800 (the board I had mentioned before)
http://www.embeddedarm.com/products/board-detail.php?product=TS-7800

Someone mentioned to me that the reason the TS-7800 appeared to have such
a slow sample rate was that TS had programed the AVR to sample at a low
rate, but apparently can go faster... so I'm currently looking into this.

The APF seems to fill my qualifications... I'm just inquiring about the
boot time atm.

However, I'll answer your guys questions and if you have any
comments/suggestions about what I'm thinking about doing please let me know
:)

----

[QUOTE] Will the board be connected to a PC while collecting data? Or is
it supposed to be a self-powered system that can collect data for you and
write it to a USB stick-type memory that you may later connect to a PC for
data processing at a later time?[/QUOTE]

It will be a self-powered system that can collect data and write it to a
USB stick, which will then be connected to a PC at later time for data
processing.

[QUOTE] Do you want all the software pre-written for data capture and
transfer to the USB memory for this device, or are you looking for
something that will allow you to write your own programs on the device
itself, as well, as opposed to only doing post-processing on an IBM PC type
machine? In other words, do you require outputs other than the USB host
port, which I assume you intend as storage for data recording?[/QUOTE]

At the moment I only plan to do data processing on a PC after data has
finished being collected. So I suppose I only need the USB host as an
output.

[QUOTE] Oh, and how many bits of precision do you need? Single-ended or
differential? Voltage range? Galvanic isolation or not? Isolation
between channels? etc.[/QUOTE]

- Around 10-16 bit precision
- I think Iâ??d like a voltage range around â??5V to +5V, but a little
smaller would also be alright.

In response to your other questionsâ?¦ honestly I donâ??t seem to know
enough to answer them. I tried reading up on single-ended vs. differential
inputs after reading your post, but I got a little lostâ?¦ from the sounds
of it explaining my project a little more in depth would probably help you
tell.

[B]Project Summary:[/B]

I will have 8 diodes (8 diodes are used to give me 4 signals) attached to
muscles on a human body. The signals will be sent through an amplifier to
bring them around the (+/-)0-5V range (thus I can adjust this gain
depending on what the MAX input is of the ADC), the signals will then be
sent through a Bandpass Filter to filter out noise and unwanted signals.

After this I need to convert the analogue signals to digital signals at a
rate of 1kHz (taking all 4 readings within this rate; thus if there is only
one ADC then it will have to be able to at least run at a rate of 4kHz/ch),
and then record the signals to USB stick-type memory.

Processing will be done later on a separate PC.


[QUOTE] An Atmel USBKey is able to do what You want.[/QUOTE]

It does seem to be able to do soâ?¦ let me confirm some things. This
device is a MCU? In order to us it in my application I would need to us it
along with a separate ADC, correct?

[QUOTE] I would build the ADC part be myself, then you can choose any SBC
solution. You can search an ADC with the parametric search engine at
Digikey:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556291&keywords=adc[/QUOTE]

Neat site, thanks a lot!

So I have a question thenâ?¦ how much more difficult is it to put together
your own unit, say as youâ??re suggesting with finding your own ADC, and
then using say the AT91SAM9G20 to write to the USB, in comparison to
finding a Single Board Computer already with an ADC, USB host port, and
Linux OS? What kind of differences would I come across? (really new to all
this)

Thanks for everyone's help!
.

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