LONWorks vs. Ethernet

I need to build some little devices to install throughout a small
building, each of which will take readings from 2-6 analog sensors
(10-bit resolution, 1 sample/sec is plenty). Some of the pods will
also need to drive a few low-power relays. I want the networking to
be all digital, with the sensor readings going back to a headless
Linux PC, which also sends signals back to open and close the relays.
The remote devices should be very cheap, and the networking should be
reliable and flexible in terms of topologies. Delivering DC power and
communications over the same cable would be ideal.

I know squat about Echelon/LONWorks, beyond the little I've been able
to figure out from reading their website, which buries the technical
stuff I need to know in mountains of marketing propaganda. But still,
it seems like it could do the job. They have a version that can do
the communications over the same two wires that provide DC power,
which is convenient. What I don't know is how I would interface ADC
chips and relay drivers to the Neuron chip, how I program the thing,
and how much the chips, transceivers, and external components cost
(ballpark, quantity 100 or so). And if the development tools are
commercial (and I hate commercial development environments), how much
do they cost, and do they run on Linux? Also, is the thing really
reliable and tolerant of less-than-perfect wiring?

The alternative is to bring out the big guns and run an embedded Linux
on an SOC/SBC and just use Ethernet (preferrably with Power over
Ethernet) and TCP/IP. This is appealing because I know Linux very
well, and I can develop for it using free tools. I suspect the
downside is the cost. I think it's worth paying a little more for the
convenience of using something I know, and which is widely supported
in all sorts of industries. But without knowing how cheap LONWorks
can be, I don't know how much of a premium I'm paying for the
convenience of Linux.

I should also say that I've considered using an 8-bit microcontroller
(eg Atmel AVR) and RS-485, but then I have to write and debug an RTOS
and network protocol, plus my experience with RS-485 has been that
it's far too sensitive to wiring imperfections, and the network
topology is too limited.

So, any thoughts? Can anybody with LONWorks experience give me some
advice on whether that's a good option, and how much cost I should
expect to save vs. Ethernet? Any suggestions of very cheap SOCs/SBCs
if I want to go the Linux route?

Thanks very much,

--
Randall Nortman
.

Relevant Pages

  • Re: LONWorks vs. Ethernet
    ... each of which will take readings from 2-6 analog sensors ... > Linux PC, which also sends signals back to open and close the relays. ... > and how much the chips, transceivers, and external components cost ... > on an SOC/SBC and just use Ethernet (preferrably with Power over ...
    (comp.arch.embedded)
  • Re: LONWorks vs. Ethernet
    ... each of which will take readings from 2-6 analog sensors ... > Linux PC, which also sends signals back to open and close the relays. ... > and how much the chips, transceivers, and external components cost ... > it's far too sensitive to wiring imperfections, and the network ...
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