programmable digital I/O.. what should I buy?

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Hi Everyone,

I want to make a programmable digital I/O device to coordinate some
experiments I'm performing. I'm not sure what to buy, please help me
out.


Here's what I need:
at least 8 channels of digital I/O
timing resolution of 10 microseconds or better
on-the-fly digital output changes based on digital input (easily
re-programmable via computer)

For example,
when channel 2 goes high, less than 10 microseconds later, five 100
microsecond long pulses at 100 Hz are generated on channel 4.


Since my timing requirements are so tight, I can't run it off of
windows to change the outputs based on the inputs. I've been told that
an RTOS (real-time operating system) running on a microcontroller is
overkill.  I only want to make one of these, but I'll use it a lot. I
can program in C++ just fine and would like a device that comes with
some software to make it easy to program. Ideally, this would be a
USB-attached device, but I'd be interested in PCI board solutions as
well.

So what should I buy?

Thanks in advance,
-james


Re: programmable digital I/O.. what should I buy?
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    I will assume that you want a PCI board for the Windows environment.

    Lets see what you need.

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    Windows (any flavor) is not real time. When the OS goes away, it
will come back when its ready.

    So a PCI board with a FIFO on the digital side would be required


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    TImers are good for this type of thing. So you need a PCI board with
a bunch of programmable timers.

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    Most RTOSs are 1 to 10 milli-second timing.  Micro-seconds they can
not do.

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   This sound like a custom design. I doubt you will find something off
the shelf.

   A PCI board with an FPGA on it may do what you want. ( those are
cheap $200-$500)

    Then you would have to learn FPGA programming or pay for programming
services.

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Good Luck, keep us informed.

Dolnald

Re: programmable digital I/O.. what should I buy?
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That turn-around time means either a local Microcontroller, or a CPLD.
Times are just slow enough to be OK on a nimble Micro, so you can avoid
CPLD/FPGA solutions.

Look at something like C8051F064EK

http://www2.silabs.com/tgwWebApp/public/web_content/products/Microcontrollers/en/mcu_developmenttools.htm

That has Two USB links, 128K RAM, and 8 IO pins on a header, with a
25MHz core - ie 10us to that is 250 machine cycles, or 100-150 opcodes.
Price is just $25, so you could use more than one if multichannel/event
SW gets too complex.

-jg



Re: programmable digital I/O.. what should I buy?
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They're not directly programmable in C++ but I use the Plug-A-Pod and
MiniPod from New Micros (www.newmicros.com). They're inexpensive and have a
built-in RTOS.

Noel

--
Noel Henson
www.noels-lab.com       Chips, firmware and embedded solutions
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