At 10:50 PM 9/5/97 +1000, you wrote:
>I am thinking of using RS-485 for hooking together some home automation

Have the receiver, if it doesn't receive a valid packet (as determined by
CRC, ChkSum, etc) reply with silence.  If the transmitter doesn't get back
an _addressed_ "ACK" signal, it times out and retries after a sorta-random
delay (say, based upon TMR0).  This would allow things to work reasonably
well.

Andy

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Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
          Hardware & Software for Industry & R/C Hobbies
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