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RS485 sniffing

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I have two pieces of equipment that communicate with each of other via two RS485 signals (one for each direction). Think of a small box with displays, buttons and rotary encoders controlling a microprocessor on the other end. I eventually want to be able to replace the box with a PC or other controller box but first I need to read and log all of the data transmitted so I can emulate it.

How can Wireshark be interfaced to tap into those lines and store the data?

Thanks, JJ

asked 17 Feb '13, 07:30

johnjohns's gravatar image

johnjohns
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2 Answers:

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Do you have a capture file of the data and only need wireshark to be able to read and dissect the RS485 protocol data inside the capture file? Or do you need wireshark to be able to capture from an RS485 interface as well?

If the latter, it would be hard. If your RS485 is coming in on a USB (ie, a RS485-USB dongle), you might be able to capture it as discussed on the tools page.

For just dissecting an already captured file, it depends on the file format - i.e, if wireshark can already read the file format. If not, then you'll have to create a file format reader, which is discussed in the README.developer page in wiretap directory of the source code. Once you can load and read a file format in wireshark, you'll need to write a dissector for the protocol to display/filter/etc. the data you want. You can either do that in C code, as discussed in the README.developer page in the doc directory of the source, or you can write it in a Lua script, as discussed in the Wireshark Lua wiki.

answered 17 Feb '13, 08:10

Hadriel's gravatar image

Hadriel
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You may try the software to monitor your ports. Really simple - see all the activity and log at you PC screen. I use this one http://www.eltima.com/rs485-sniffer.html, but you may try the others.

answered 28 Sep '16, 05:46

GordonNelson's gravatar image

GordonNelson
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