Sherpa,

Thanks for your replay,
I have max1482 chips that I can use.
A few things are not clear for me lets assume
I got 30 slaves and 1 master if 2 slaves try to
Communicate with master at the same time then what will happen?
I2C is kind of different it will wait until the bus gets free
Do you know there rs485 mostly are used ? is there any chip to make
I2C work for long distance ?

Thanks again

Andre


>>>>>>>>>>>>>>>>>>>>>




If you use 4 wires it is RS422.  RS485 uses 2 wires, but you can only
communicate in one direction at a time.  For your use I think RS485 (2
wires) should work fine as long as you have one master and a number of
slaves.  The slaves only speak when spoken to by the master.  If the
master wants to know if the gate is open, it asks.  Basically the master
polls every slave periodically to see if they have info.  But the master
can issue commands any time he wants as long as a slave is not replying
to his previous command.

Sherpa Doug

> -----Original Message-----
> From: Andre Abelian [mailto:engelec@EARTHLINK.NET]
> Sent: Thursday, February 21, 2002 4:24 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]: 120 feet bidirectional commnucation
>
>
> Hi to all,
>
> Soon my electronic gate will be ready witch is
> About 120 feet far from my desk and I need to
> Build bidirectional communication with whole
> House there are doors and switches I need to know
> The status of it. My favorite interface is I2C but the problem
> Is that I2C is not good for 120 feet distance I guess my
> Choice is RS485 differential phase but what I do not know is
> By using 4 wires 2 for receive and 2 for transmit can I communicate
> with all 35 sensors ?. So rs485 works like rs232 I do not see any way
> of sharing from same bus I need to make communication like I2c but
> for 120 feet long any help will highly appreciated.
>
> Andre
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads
>
>
>

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics