You can run RS485 with 4-wires for full duplex operation. Best Regards David Huisman ----------------------------------------------------------------------- ORBIT COMMUNICATIONS Reliable Wireless Solutions (Telemetry, Control, Monitoring ...) Website : http://www.orbitcoms.com PO Box 3469 Tuggerah NSW 2259, AUSTRALIA Phone: 61-2-4393-3627 Fax : 61-2-4393-3685 Mobile: 61-413-715-986 ----- Original Message ----- From: "Douglas Butler" To: Sent: Friday, February 22, 2002 8:26 AM Subject: Re: [EE]: 120 feet bidirectional commnucation > 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 > > > > --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.323 / Virus Database: 180 - Release Date: 2/8/02 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads