On 2010-12-19, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
David Billington fired this volley in
:

Any idea what language you'll
be using, my experience is with C and C++.


I can do C, and a smattering of C++. I retired from software work before
C++ had a full following among industrial users, but C was well and
thoroughly rolled out.

However, I'm most likely to do it in Visual Basic. It's not all that
great a language in terms of efficiency, but I have a library of hardware
functions and widgets that claim to deal with all the preemption crap.
Obviously, at 4800 baud, interrupt latency is important. Coupling that
with the fact that the control will choke if you send more than three
characters past the XOFF makes real-time handling pretty important.


Dave, I could not figure out how to make the control use Xon/Xoff "dumb"
protocol for the DNC. I followed your instructions of using a "-1" as
the filename, but my termulator still just blithely sent the whole file,

"termulator"? "Terminal Emulator" perhaps?

rather than pausing per-block. I don't yet have a protocol analyser
hooked up, but I presume that means there were no flow-control characters
coming from the control.

Does the control support hardware flow control? The CTS/RTS
lines to tell when to stop and start? Sometimes that will work when the
software DC1/DC3 (also known as Xon/Xoff) won't.

And -- it should result in an *immediate* halt to the
transmitted data if the port is set up to honor it. The program may
have more characters queued up, but they can't go out until the CTS line
on the transmitting system goes true.

OTOH, I can transmit a DNC stream successfully from EZlink, using ONLY a
"-" as the filename (at the control) and two executes. The first one
seems to set the protocol, and the second starts the DNC link.

Perhaps you could explain that -- what is the significance of the "bare"
minus sign as a filename?

On Windows, I don't know. On unix systems, it says "write the
data to "standard output"" (which normally would go to the screen, unless
you follow it with a pipe symbol '|' followed by another program to
receive the data. (It also can mean to read from "standard input",
which would be the keyboard, unless the program name is *preceded* by a
pipe symbol, with another program writing to standard output feeding the
pipe.) Back in the old days, MS-DOS *faked* pipes by writing to a
temporary file, then closing it when the program ended, and opening the
file for reading when the next program started up. (No preemptive
multi-tasking on old MS-DOS. :-)

I just did that from rote per the EZLink
instructions, but have no idea what it does. Can the DNC protocol be
invoked with a "real" filename, also? (haven't tried yet)

No clue there, since I don't know the program, and I don't see
your command line there -- or did you type the '-' to a GUI field?

I air milled several parts yesterday under DNC via EZLink.

Good! Next wax. :-)

Enjoy,
DoN.

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