"Steve Lusardi" wrote in message
...
Larry,
You normally have your act together, but not this time. Meindert is
correct about his stated risks, but he is overstating the cost
of Ethernet solutions. Today they are canned in firmware and reasonably
priced. The savings in installation complexity,
drastically increased speed and system flexibility far exceeds any
increase in component cost. Please don't get me wrong. 802.11
has its place, but not in systems where data integrity are safety issues.
CAN solutions work well and meet equipment
manufacturer's requirements, but as an end user I must counter with a
standardization argument. The only thing that is standard is
the CAN pipe, everything else is proprietary and manufacturer unique. The
ability to mix and match instruments and devices from
different manufacturers would virtually disappear. Furthermore, the CAN
bus is slow in relation to Ethernet, reducing the amount
of net users and traffic the pipe could ultimately handle. Then there is
the question of physical pipe length and noise
susceptibility. Ethernet has it all covered, but Meidert and I have had
this discussion a while back and I didn't convince him
then. Maybe today, he's older now.

And you still cannot convince me of the idea that an ethernet interface can
be as cheap as an RS-422 interface. The canned solutions you talk about
still cost considerably more than a simple Rs-422 tranceiver chip. Of course
I could have taken an ethernet version of the controller I use in my
multiplexers, but I still would have to add a transformer and at minimum a
UDP stack and, if you want the ease of ethernet, the complete DCHP stuff to
the existing software. You simply cannot compare a dedicated non-mass market
device to mass market PC stuff which cost next to nothing for two purposes:
1) a huge market and 2) a complete multi megabyte OS to support the dumb and
cheap hardware.

This is the same discussion as with Bluetooth. You can buy BT dongels for a
couple of dollars/euros but these rely on Windows to operate. The modules I
use cost 20 times that much because 1) the volume is much lower and 2) they
contain a complete processing system to do what windows would otherwise have
done.

Meindert