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
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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.
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
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or Z-world
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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
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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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