Re: Your Opinions please

["mark_harrison_uk2" <mph@xxxxxxx>]

--- In ukha_d@xxxxxxx, "Ian Davidson" <ian@g...> wrote:
Ian,

Just done a few calculations after your comments about xAP being too
heavy.

A xAP message in the X-10 xAP schema to turn on a light is typically
about 160 bytes, which is to say 1280 bits.

So a transport running at 2400bps would have a latency of about .5
second, which isn't great, indeed only slightly better than the "in
the field" latency on my X-10 installation at home. (Or about 1/16th
second on 19,200).

An alternative is to work, say, how the xAP-CBus gateway works, and
have a software application that runs transcodes from your protocol
to and from the xAP world.

The quick and dirty solution is, of course, to write a quick PC
application that takes xAP messages and outputs your protocol in
an "on the wire format" to a serial port, then use something very
low
power to do the media conversion. It might be sensible simply to say
that the serial port HAD to be run at 2400bps which makes the
buffering somewhat easier.

An alternative, however, would be to use a Rabbit-based design to
talk from xAP-on-ethernet to yourprotocol-on-serial, and then add a
daughterboard that media-converted. Trouble is, Rabbit chips are
still expensive unless you ramp up volumes quite high, and there
aren't that many cost-effective alternatives to add ethernet support.

If you are interested in collaborating on this, drop me a note...
Certainly, I can make the xAP-serial source code used for the
HomeVision connector available to you, which contains port handling,
xAP message parsing, and coding to a proprietary protocol.

Regards,

Mark