Re: Data Acq. Concept Help
- From: "schmoester" <to_schmoe@xxxxxxxxx>
- Date: 20 Jul 2005 07:08:45 -0700
Hi Martin,
Thanks for the reply. That's a great concept.
I have just a couple issues:
I've got nine of these modules, each of which have to send their data
to a central computer. To have each board have it's own ip address (5
bds x 9 modules = 45) seems like too many for the central computer to
talk to, versus say nine. I'm sure it can be done, but what do i use
for a hub? One per module and another to collect the modules I guess.
If I were to use an single Xport per module, how would I get the data
to it from the 5 daq boards in each module? I was thinking USB--maybe
just replace my PC-104 board with a custom board with an XPort on it?
You're right, there's a lot of software to be done. I'm very much
interested in simpifying, and I agree, my concept seems overly
complicated. I also thought USB on the cards would also facilitate
bench testing them.
Thanks again for your help!
martin griffith wrote:
> On 19 Jul 2005 13:29:52 -0700, in sci.electronics.design "schmoester"
> <to_schmoe@xxxxxxxxx> wrote:
>
> >Hi,
> >
> >I've got ~220 low-freq. (0 to 4V max) signals to measure and send to
> >another computer (over ethernet).
> >
> >This group of signals will be handled by a single data acq. module
> >physically separate (20 meters) from identical others, all connected by
> >an ethernet bus.
> >
> >Module Concept & Reqmts:
> >--PC-104 CPU board with USB and Ethernet interfaces. Ethernet to other
> >modules, USB to custom DAQ boards, described below.
> >--Want to divide-up the 220 inputs into ~50 per board, -> ~ 5 boards,
> >spare channels good.
> >--High Common-Mode voltage (< 200VDC) on some inputs, -> difference amp
> >front end on some channels. (LTC1990)
> >--Digitize signals (12-bit) with I2C ADC's (thinking MAX1238)
> >--Offload data from boards to local PC via USB. Would like to use the
> >Cypress EZ-USB or the Cypress PSoC with USB onboard (CY8C24794). This
> >would be the I2C to USB bridge. I want to keep the USB interface and
> >not use only I2C controlled by PC-104 board.
> >
> >Questions:
> >--How do I buffer the data on the DAQ boards until I can read it off
> >with the USB interface? Will the CY8C24794 PSoC with an M8 µC or the
> >8051 µC on the EZ-USB interface with external memory (onboard flash on
> >the PSoC has too few read cycles to use continuously). Perhaps the
> >8051 is more suitable than the M8 for interfacing with external memory.
> >
> >Any PSoC experts that wouldn't mind some additional questions down the
> >road if I go that route?
> >
> >Thanks for sharing your insights!
> >Omar
> Seems an utterly horribly complicated method for getting a slow
> speed DAQ system into an ethernet connection.
>
> Ignoring the input conditioning, I'd start with say 64 NS's adcs7478
> spi adcs per board. Poll them with a 8051, (since I never did get
> around to learning the msp430) That 64*2 bytes per board times your
> sample rate, say 50s/sec. A massive 6.4KB/sec.
> Might have to put 8K of external ram on the 8051, dammit
>
> Feed them into a Lantronix Xport or eqiuvalent, and give them
> individual IP addresses
>
> Whats the software budget for this?
> Or am I missing something?
>
>
>
> martin
.
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