Serial data bus help needed [CROSS-POST]

Ethernet !

--
Best Regards:
                     Baron.

correction

no

Try one of these instead...

Its a relay that can be controlled over a lan. It even contains a web server so you can monitor it's status. They have multiple output versions and some with inputs.

"CWatters" wrote in news: snipped-for-privacy@corp.supernews.com:

Hell yes! Just imagine the fun Flanders could have had in Sounding Brass, telling Swann that his lightswitches were on the internet. >:)

That *nearly* meets the OP's specs if he uses 10-baseT ethernet. (serial, 10Mb/s, error correction) but unfortunately isn't a bus and with the modules at ~$100 each, may not be that attractive to a hobbyist.

OTOH if he scrounges up some old RTL8019 network cards (probably the best in terms of easy availaibilty at scrap prices and free code on the net to drive it from an 8051), he could run 10-base2 Ethernet which

*fully* meets the specs he gave us (good up to 185 m) and would be even more fun than the *neat* bit of kit you showed us :-)

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Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED)
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More flexible and comes with source.

donald

Why do you need to run at 10 Mbps to control locks and lights?

The human eye barely detects the flicker of lights running at 50 Hz so a delay in switching a light of 20 ms will be unnoticable. Locks, which will ultimately be electromechanical, will not respond is much less than 50 ms.

Start by deciding how many items you want to control and the required response time. The number of tiems will determine the message length and the speed of response the data rate. You'll probably find that running at 9600 bps will be quite fast enough.

Wireless such as Zigbee or Zwave might be more convenient.

--
Jim Backus running OS/2 Warp 3 & 4, Debian Linux and Win98SE
bona fide replies to j  backus  jita  
demon  co  uk

Yes, but this is only phase 1... who knows what kind of stuff i'll want to send thru that bus in the future... I've arbitrarily chosen 10 Mbit/s because it seems possible for such distance and yet it can support a large number of devices connected, maybe some of wich will require more than ON/OFF control. Ethernet is out of the question because i don't want to pull cat5 cable to every little device i have there and also don't want to have walls crawilng with switches or hubs or whatever.

And i don't want something propriertary and already "key-in-hand" done - i can't program that sort of stuff and it kills hobbyst movement idea alltogether. And all those corporations making gadgety stuff appear and dissapear over night or at least they forget their old buyers when it's time to sell something new.

I searched for an idea if this already exists - why re-invent it? If it doesn't i'll design my own data bus that willl be capable to comply with my requests or more. It just prolongues the whole project by month or two.

Thanks anyway

pull

CAT 5 is about the cheapest wire you can get. Even if you didn't use Ethernet you would probably want to use CAT 5 wire.

Ditch the hubs and go for RG58 AU 10Base2 ethernet. At least it can be daisy chained!

Any *wired* solution except Ethernet will be lucky to reach 1Mbit/s 10 to 100 Kbps will be *far* more achivable.

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Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED)
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Did a test on a 60 meter piece of CAT.6 cable with oscilloscope, comparing the signal on entry and exiting signal after a roundtrip thru my appartment (wich included going over or next to CRT TV's, heaters, power lines, etc.) @

10MHz square signal (my oscilloscope is way to old to go over that) and signal distortions were close to none... I'm gonna build a differential signal generator and receiver today too see if i can fix the noise and distorsions a bit more.

Currently with any luck i'd be able to squeeze in about 2 Mbit/s useful data into this system (wich is way over what i need for phase one), plus about another 1.5 Mbit for error corrections, serial device addressing and other overhead, i've not yet decided on protocol, but it will probably be similar to USB, although not at all compatible ;-) So if I manage to clean up signal a bit more, i should have near-10Mbit/s experience on a 50 meter bus. The cat6 cable is declared to carry 250 MHz, i hopefully will ever need only 1/10th of that clock speed :-)

Another idea i've had is to create "smart" signal repeaters along the line since latency isn't really an issue, at least not now. They'd read the bit-stream, analyze it, check if data+address bits "hash" agree with control bitstream and if yes, forward it further on the line... if no, signal repeat. But i'm gonna hold on this complication until i've got no other smarter solutions.

My head hurts :-p

Boris

appartment

@

data

similar

i

control

It sounds like you are making a lot of work for yourself. Can't you use something like X10 or it's later rivals?

There's no fun in that!

Good point.

I took the systems engineering approach of looking at the stated requirement and proposing an approriate solution. Unless you intend to run streaming audio or similar, I still think that a slower speed could do everythng you want.

At 10 Mbps you'd certainly want a balanced line system, which is what Cat 5 cable is designed for. As for protocol, synchronous data would be the way to go, even though somewaht more complex. Again Ethernet runs synchronous data (AFAIK). It may be that balanced line drivers and receivers designed for ethernet would be the best components to use.

Final comments: although people refer to Ethernet, they almost certainly mean TCP/IP over Ethernet. Raw Ethernet data protocol is simpler and could still be useful to you even if you don't want to follow an existing standard. Just because you don't want to lock yourself into a proprietary standard doesn't mean that you shouldn't use existing technology. Keep your brainpower for solving your control needs not reinventing low level protocols.

--
Jim Backus running OS/2 Warp 3 & 4, Debian Linux and Win98SE
bona fide replies to j  backus  jita  
demon  co  uk

I agree! Raw Ethernet was inferred, although I was thinking more co-ax rather than USTP particularly since the transceiver chips are cheap.

--
Best Regards:
                     Baron.