Home/Support/Support Forum/WR21 Serial Port 485 Modbus
Welcome to Digi Forum, where you can ask questions and receive answers from other members of the community.

WR21 Serial Port 485 Modbus

0 votes
Hi all,

I'm trying to read modbus data from a RS485 device using a Digi Transport WR21 but I'm completely lost on this issue. I've been reading the examples available on the Digi ESP libraries, but have no luck so far.

Wondering if there's a working example for opening and send data to the serial port of a Transport that is configured as RS485.

I've seen so much information on the forums but most of it it's related to Xbee 485 adapters.

I think I'm missing some clues about:

1) Connecting the serial port of the Transport to the 485 device. I think it should be:

TDA-RDA (together)
>> RS485 +
TDB-RDB (together)
>> RS485 -

2) Setting up serial port on the Transport properly (where is the option TCP packets, do I need it?

3) Managing the port propertly from python. So far I'm using the serial libraries without any luck so far.

There's so much that I don't know about python and serial since I'm new to it, so I was looking for kind of working example to start from.

Sorry for writing so much and thanks a lot in advance for your help.

Regards.
asked Aug 1, 2013 in Python by fohmlt New to the Community (2 points)

Please log in or register to answer this question.

3 Answers

0 votes
I found myself the answer to question 1 in this excellent wiki, wich I assume that applies to Transport products too:

http://www.digi.com/wiki/developer/index.php/RS485_DB9_on_Connect_Products

I'll continue working on the other points, so your help is still very much appreciatted. Thank you.
answered Aug 1, 2013 by fohmlt New to the Community (2 points)
0 votes
Oh sorry.. I didn't see that you already found the answer for this yourself.
answered Sep 26, 2013 by MartinezJ New to the Community (7 points)
0 votes
You are right about the connections; usually always positive connected to positive and negative to negative when dealing with RS485.
answered Sep 26, 2013 by MartinezJ New to the Community (7 points)
...