Re: Re: Device discovery for control/sensor schemas

["John B" <home-automation@xxxxxxxxxxxxxxxx>]

---- Original Message ----
From: g8kmh <lehane@xxxxxxx>
Sent: Wed, 24 Nov 2004 22:22:47 -0000
To: ukha_xpl@xxxxxxx

>
>
> > Hi all,
> >
> > Many of the recent xPL apps are making use of the sensor/control
> schemas, as these make it much easier for devices to interoperate.
> >
> > However, there is no way of finding out a list of valid devices
> that a particular xPL connector supports.
> >
> > If we take DMX as an example, we can send a message like:
> >
> > control.basic
> > {
> > device=3
> > type=dmx
> > current=255
> > }
> >
> > This will set channel 3 to level 255.
> > But how do we know what channel 3 actually is?
> > Or even if channel 3 exists at all?
>
> ..and of course even if it does exist, has it set it to 255?

If it has, it should issue a control.confirm message to confirm that the
operation succeeded.

> >
> > We should be able to be given a list of all known DMX channels,
and
> a friendly description of what is connected to them.
> >
> > The same issue applies to things like the C-Bus connector - you
> shouldn't have to remember the C-Bus group address of the light(s)
> you want to control - you should be able to be presented with a list
> of all detected devices.
> >
> > The question is: Should each xPL connector be responsible for
> maintaining a list of "friendly" device names, and mapping
them to
> actual device names, so you'd be able to send something like:
> >
> > control.basic
> > {
> > device=lounge_lights
> > type=dmx
> > current=255
> > }
> >
> > Or should it be up to a controller like xPLHal to store this
> information and do the mapping between friendly devices and actual
> devices?
> >
> With intelligent devices there may be no connector. Looking forwards
> there may be semi-autonomous devices (for example the NETIOM module)
> which interoperate entirely separately from xPLHal, bar
> configuration. xPLHal because right now there isn't another
> configurator as far as I'm aware.

I think there is a stand-alone configuration tool, but most people just use
xPLHal.

> My view is it is up to the device or connector to maintain the
> friendly names and there needs to be some means of configuring a
> device with these alias/es at startup. Therefore it would need to
> announce the unit(s) it controls.

The idea of a "master" device seems to be what others are
suggesting, and asking the master to report details on all devices it
controls seems a suitable way of achieving this.

> DMX presents some more interesting
> problems since a connector may support 512 channels (in practice
> probably no more than 64) but it has no idea which devices are where.
> Worse, you could add devices on channels ad-hoc and the controller
> never knows.

Yes, the same is true of X10 as well - the controller has no idea what's
out there, or what to call it.

> I think universiality is the key and probably worry less about the
> small devices - PIC's, etc, are becoming available with more memory -
> after that it's only code!

OK, so what we're basically saying is that for small devices, things stay
as they are.
But for a more capable device, it should be possible to assign friendly
names to it's endpoints via an xPL message, maybe issued by the controller
or by a stand-alone app.

Regards,

John