Re: Re: RS485 - XPL on the wire

["Mal Lansell" <mlansell@xxxxxxxxxxxxxx>]

Collisions are a problem in HA - X10 suffers from this kind of
unreliability.  Items may not be transmitting often, but there may be peaks
of traffic around a single event - a computer sending out instructions to
several devices in response to a single command, for example.  It would be
preferable for collisions to be dealt with robustly.

As for DMX, it would be fairly straighforward to write an xPL enabled
driver
to send DMX messages via an RS485 interface.  However, DMX messages need to
be sent continuously, so to unburden the PC (and avoid all the lights going
off it it needs to be rebooted) it may be preferable to have a dedicated
hardware controller instead.

Mal


----- Original Message -----
From: "g8kmh" <lehane@xxxxxxx>
To: <ukha_xpl@xxxxxxx>
Sent: Friday, October 22, 2004 12:15 PM
Subject: [ukha_xpl] Re: RS485 - XPL on the wire


>
>
> Indeed, the original intention was xPL on RS485..since xPL already
> has addressing. I took a rather simplistic view that in HA you could
> afford a few collisions and that devices aren't transmitting very
> often. It was also only around simple devices like light switches,
> temp sensors, etc.
>
> Others have mentioned DMX/DMX512 and I think there is a great case
> for an xPL to DMX interface to drive dimmers.
>
> I also found this:
> http://caraca.sourceforge.net/
>
> Lehane
>
> --- In ukha_xpl@xxxxxxx, "Mal Lansell" <mlansell@f...>
wrote:
> >
> > > Hi All,
> > >
> > > http://www.hth.com/easytap/default.htm
> > >
> > > May be of interest.......
> > >
> > > I've alsways thought that RS485 was mainly about the
"hardware"
> layer.
> > >
> >
> > It is, but I think the OP wanted a method for transmitting xPL
> messages over
> > RS485, as opposed to something like DMX, where xPL would be used
> (by a PC
> > application) to drive a DMX controller that then sends DMX
messages
> over the
> > RS485 connection.
> >
> > For sending xPL over RS485, we get to define our own unique
system,
> although
> > in the absence of a definite application or hardware for this,
it's
> hard to
> > say whether RS485 or some other network (such as CAN or Ethernet)
> would be
> > more appropriate.
> >
> > Mal
> >
> >
> >
> >
> >
> > > SNAP,  http://www.hth.com/snap/ which I know
many are aware of,
> is one
> > > protocol that can sit on RS485, as indeed is DMX512
> > > http://www.dmx512-online.com/physl.html
, if I've got this wrong
> feel free
> > > to take me into a dark corner and tell me so.
> > >
> > > Regards
> > >
> > > Stuart
> > >
>
>
>
>
>
>
> xPL Links: http://www.xplproject.org.uk http://www.xplhal.com
http://www.xpl.myby.co.uk
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