Re: Re: Sensors / Switches / etc

["Dan" <dtoma@xxxxxxx>]

Hi Patrick,

Let me comment through the lines...

> - Convenient, existing TCP/IP network is already in place whereas the
> serial one isn't.

You can use the same CAT5 cabling for serial communication. More, you can
have a single bus for all the devices, so no need for HUB/switches or
supplemental RJ45 sockets and the respective cable

>
> - Serial networks require a purpose built hub if they are to be used
> with conventional star-topology cat5 cabling

You can use a daisy-chain topology with CAT5 too... if you have let's say
several serial devices in the same room you can put all of them on the same
wire.

>
> - Fast. Time lag on a multi-device serial bus can be a big issue.
If you consider let's say X10, where the time lag is sometimes very big ,
this is not an issue in a well designed serial bus (do not forget 10BaseT
ethernet-10MHz on the same cable). I think that home automation devices do
not need a very fast connection (maybe with few exceptions..).

>
> - Integrates with existing PC based controllers quickly and easily
> (no need for serial-ethernet bridges or a spare serial port)

If you have a minimum of ONE PC, then the bridging is not an issue anymore.
Do not forget.... I do not talk about a classic PC serial connection but
about a single wire bus.

>
> Best compromise in terms of cost/performance:
>
> - Put an ethernet to serial bridge in each room, connected to the
> cat5 TCP/IP infrastructure.

For what reason to do that? You can have a single ethernet RJ45 in that
room
and use 2 spare wires for the serial bus.... So you can hava a PC and the
serial bus on the same cable.

>
> - Use serial locally for a limited number of devices (e.g. temp
> sensors etc) which are connected to the ethernet bridge.

My opinion for the best approach is to mix between ethernet and a
single-wire bus devices, with the cost as the main selection factor. This
can be a lot more difficult to design, but... this is not the nice
part?...;-)

Dan

>
> Patrick
>