Jul 28

Modbus/RTU via TCP Serial Gateway with Ruby

We recently had a need to connect to a PowerLogic BCM42 through a Barionet-50 from Barix. While the Barionet-50 speaks Modbus/TCP for itself, it does not perform as a TCP/RTU gateway for devices hooked up to it via the RS485 port which is a straight serial gateway. Our project is being implemented in ruby so we started with the excellent RModbus gem and modified it to send Modbus/RTU commands via TCP and it works perfectly. This solution is also significantly cheaper than buying an off-the-shelf Modbus TCP/RTU gateway as those tend to *start* at about $400 and rapidly get more expensive.

 

require 'rubygems'
require 'rmodbus'
ModBus::RTUViaTCPClient.connect('10.10.100.33', '10002', 4) do |cl|
        total_ma = cl.read_holding_registers(0, 42).inject(0) { |acc, i| acc += i; acc}
        puts "Total mA: #{total_ma}"
end
$ ./test.rb
Total mA: 12510

Our code for accessing Modbus/RTU devices via TCP can be found at http://github.com/kreynolds/RModBus

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About Kelley Reynolds

The CTO of RubyScale, and an experienced software engineer. If Kelley isn't working on a project, you can probably find him hacking on a huge dataset, swimming a marathon, or spending time with his family and small menagerie.
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Discuss: “Modbus/RTU via TCP Serial Gateway with Ruby”

  1. July 6, 2011 at 11:32 pm #
    Reply

    Looks very handy.On ruby 1.9.2p136 (2010-12-25 revision 30365) on OS X I’m getting the following error:ruby test.rb/opt/local/lib/ruby1.9/gems/1.9.1/gems/rmodbus-1.0.2/lib/rmodbus/tcp.rb:34:in `[]‘: can’t convert Symbol into Integer (TypeError)Anyone else seeing that?

    Posted by wayer

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