RS485 2 wires on Digi one IAP

Question

The RS485 port 1 work perfectly well using 4 wires cabling. Unfortunately, our Modbus slave uses RS485 2 wires only. What is the configuration or the cabling to use a 2 wires RS485 on port 1 instead of a 4 wires RS485?

Answer 1

Port 1 is the screw terminal. Keep in mind that we tie the rxd/txd +/- pins together when the device is in two wire mode.
You can use 3, or 6 for the + signal. And 4, or 7 for -. We also recommend that you use pin 5 gnd.

Comments

Thank you very much for your answer! For the cabling, no problem of course. But I did not see any command to put the IAP in 2 wires mode in the configuration wizard. Is there a special command to use with telnet or tying the pins together is enough?

Answer 2

RS485 is enabled using the dip switch for the serial port. I have included a link to the quickstart guide which show the different modes used by the Digi One IAP.

http://ftp1.digi.com/support/documentation/90000634_E.pdf

Comments

Thank you very much, it works now!

Answer 3

It'd be really cool if this were documented in a manual somewhere. Maybe include some example wiring diagrams like the rest of the industrial controls world?