Suggestions for SBC with lots of digital IO?

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I'm looking for suggestions for a single-board-computer to control a large
power supply.  The power supply is able to turn various channels on/off, and
communicates to a host processor via RS-232.  It needs (approx) 23 digital
inputs capable of detecting the presence of a voltage up to 28V, 4 analog
inputs, and about 70 digital I/O lines capable of pulling 28 V to ground.

We'll be programming this in C.  I've looked at some of the Tern products
(www.tern.com) like the P300 but am not sure about their Paradigm
development environment.  They don't seem to support the use of any OS.
It'd be nice to be able to run Linux on it.  I've also considered a PC/104
solution but haven't found any with enough IO lines.

Any suggestions are much appreciated!

- Mark




Re: Suggestions for SBC with lots of digital IO?

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and

Why the heck would you want to compromise the integrity of a simple app like
you describe with a bloatware OS like Linux (or any other GP OS for that
matter.  You probably don't need anything more than a trusty old One Big
Loop structure.  Check out PLC like boards from people like Splat
(www.splatco.com) or Z-world (www.zworld.com).  You might find that you need
two boards want a couple of boards to get you 70 I/O.

The paradigm environment is basically the old Borland compiler evolved and
optimised for embedded products.  I'd trust it more than than anything with
1 million lines of someone else's code underneath it (read anything hosted
on a Micro$oft, *nix or similar sized OS).

I guess it depends on how critical it is that your app keeps running.

Cheers,
Alf Katz

snipped-for-privacy@remove.the.obvious.ieee.org


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Re: Suggestions for SBC with lots of digital IO?
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Mark,

Not sure if we've ever talked regarding your application (it sounds
familiar so I suspect we might have), so apologies ahead of time if
I'm repeating myself.

I'm not aware of any competitors with enough I/O to deal with 93
high-voltage digital I/O... certainly not on one board!  From a
price/efficiency perspective, the P300 board is a perfect hardware
choice.

But, I also understand your concerns about the development
environment.  Embedded Linux is a oft-wished "extra" that our systems
don't support (not in a practical beyond-the-demonstrator sense,
anyways)... but let me just say that for many of our customers who've
asked about Linux, they're more looking for the "brand" name (who
woulda thunk it 5 years ago, Linux is a sellable brand name!) than the
actual functionality offered by Linux.

Let me ask rhetorically...

Are you really running a multi-user environment on this system?  Do
you really need task protection?  Do you really need a multi-threaded,
as well as multi-tasked environment?  Are you really going to run the
network services Linux supports?  Do you need ext2fs?  Are you going
to update your system with .rpms, or run StarOffice?  Interface with
PC peripherals?

If your answers to the above are a series of "yes", then I'd suggest
you start with one of the "industrial PC" products on the market
(which tend to run $500+), and then look for compatible digital I/O
expansion boards.

If your answer is *no* (and it usually is for most industrial/embedded
environments), then I've got to think the Paradigm development
environment + TERN software libraries is everything you need.  Low
overhead, capable of executing in real-time, easy access to onboard
timers/interrupts, dynamic memory, C drivers for accessing all of the
digital I/O on the board, DMA/interrupt-driven serial port drivers...

Is there anything you want your board to do that you won't be able to
build with the above?

From the point of view of a TERN employee, of course I hope the answer
is 'no'. ;)  If you're not sure, drop me an email and let me know what
type of *behavior* you're looking for.  Be more than happy to talk
implementation strategy with you.

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