Re: Your Opinions please

["mark_harrison_uk2" <mph@xxxxxxx>]

--- In ukha_d@xxxxxxx, "Dave McLaughlin" <dave@v...> wrote:
> Hi Mark,
>=20
> Excuse me for being a bit cynical, but 160 bytes just to switch on=20
> a light is a bit heavy going.=20

You are joking, aren't you? The Microsoft Home Control Protocol has a=20
message size of about 22k (ie - 1500 times the size) to accomplish=20
the same thing.

Of course, if you're writing a protocol ONLY to do something very=20
simple like turn lights on and off, then you can write it small. You=20
can switch on a light in a couple of bytes...

If you're writing a general protocol like xAP, then you can't. Hence=20
the need for translation onto the HA equivalent of the "last
mile".

The question is - which would you prefer? A protocol that's common=20
across large classes of devices, and multiple computer platforms, or=20
yet another proprietary protocol for yet another proprietary bus.

The largest domestic xAP installation runs primarily on an RS485 bus,=20
has over 120 devices on it, and still runs very fast in the field.

The difference in price between a PIC with 2k and 64k is, AIUI, a=20
matter of pennies not pounds. With X-10 modules at =A315-20 a pop, the=20
difference is a few percent of the cost. The difference in capability=20
is huge. I would say that the current price-point of X-10 modules HAS=20
to be a realistic target...

Over the last 10 years, the price of (disk, memory, etc.) has fallen=20
by a factor of about 2,000. Even if it only falls by a factor of 500=20
over the next 10 years, that's still enough to make a couple of=20
hundred bytes fine for fractions of pennies.

Now, I will concede that there IS still one place where ultra-low=20
bandwidth / processing power is king, and that's in mains-modulated=20
data...=20

... but I would predict that market to have been completely overtaken=20
by wireless in the next 5 years (unless one of the much-vaunted high-
bandwidth mains projects finally goes mass-market.)

Mark