At 10:50 PM 9/5/97 +1000, you wrote:
>I am thinking of using RS-485 for hooking together some home automation
>bits which all can Tx & Rx. The Rx bit is easy but what if two or more
......
I've done rs485 half duplex, bus topologi, command-response/polling protocol.
please look at my page, packets for master to slave are
;    SYN STX DEST    'P' ETX
;    SYN STX DEST    'S' FROM    CNT DATA..DATA ETX
and for slave to master:
;    SYN STX MASTER  ACK ETX
;    SYN STX MASTER  'D' TO      CNT DATA..DATA ETX

I know this is not perfect, no checking for data and maybe too many overhead.
But, it is enough, it works :) and I've tested it using hc11(master), PC
and 8031.
goodluck.
www.poboxes.com/f
f