To my Knowledge, there is no multidrop current loop. IT is all daisy chained IE : Controller -----> unit one -----> unit two -----> unit 3 <------------------------------------------| So basically the signal goes around in a loop from unit 1 to unit 2 to unit 3 and back to the controller :o) If you need multidrop I would recommend RS-485, as the chips are easily available :o) Regards, Kat. ____________________________________________________________________________ The information contained in this email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please promptly notify the sender by reply email and then delete the email and destroy any printed copy. If you have received this email in error, you must not disclose or use this information in any way. ____________________________________________________________________________ ----- Original Message ----- From: "Christian Dorner" To: Sent: Monday, September 03, 2001 8:09 AM Subject: [EE]: RS-485 vs Current-Loop Hi Piclisters! I see a lot of people in the list build PIC networks (i.e. for home automation purposes) using RS-485. I also have seen some industrial units (sensors, controllers, ...) using someting like a "multidrop" current-loop system. Now i'm not sure what i should use when i want to connect several PIC's over a long distance? (hundreds of meters) I prefer the simple and stable (and of course cheap) construction of the current-loop sender and receiver units, but have a little worry about the total current on the bus when some receivers are connected. I think about a single (data) wire for TX and RX, simple construction with a transistor in the TX part and a optocoupler in the RX part (and of couse some resistors and diodes ...). On the other hand ist pretty simple just to use a chip to interfacing to RS-485 Bus. Has anybody recommendations what to use or some experience with a "multidrop current-loop"? Thank you for your help in advance. cu, Christian -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body