Next release

  1. Fixed bug #30 in parsing command 'write_register' for server implementation part.

2013-10-28 Release 1.2.2

  1. Fixed issue #29. The server part supports 2000 of coils/discrete inputs for reading instead of 125.

2013-06-28 Release 1.2.1

  1. Fixed issue #27 for read_nonblock error on Windows

2013-03-12 Release 1.2.0

  1. Transaction number mismatch doesn't throw exception in TCPSlave#query method. Now this method will wait correct transaction until timeout breaks waiting.
  2. Added ruby-2.0 experimental compatibility

2012-07-17 Release 1.1.5

  1. Fixed issue #24 for RTUClient.

2012-06-28 Release 1.1.4

  1. Fixed issue #23.
  2. Improved speed of the RTU\RTUViaTCP part.

2012-06-06 Release 1.1.3

  1. Fixed issue #22

2012-05-12 Release 1.1.2

  1. Fixed issue #20

2012-04-12 Release 1.1.1

  1. Fixed issue #15

2011-10-29 Release 1.1.0

  1. Fixed issue #12. Added option Slave#raise_exception_on_mismatch to turn to check response and raise exception if it's mismatch.
  2. Added pass options :debug, :raise_exception_on_mismatch, :read_retry_timeout, :read_retries from clients to slaves
    @cl.debug = true

    @cl.with_slave(1) do |slave_1|
      slave_1.debug #=> true
    end

    @cl.with_slave(2) do |slave_2|
      slave_2.debug = false
      slave_2.debug #=> false
    end
  1. Deleted dependency with serialport gem. Install it manual for using RTU

2011-08-10 Release 1.0.4

  1. Fixed issue #11

2011-07-17 Release 1.0.3

  1. Fixed issue #10
  2. Added new options for TCPServer#new and RTUViaTCPServer#new :host - ip of host server (default 127.0.0.1) :max_connection - maximum (client default 4)

2011-07-1 Release 1.0.2

  1. Fixed issue #9

2011-06-30 Release 1.0.1

  1. Fixed issue #8

2011-06-27 Release 1.0.0

New API for client part of library

Example:

    require 'rmodbus'

    ModBus::TCPClient.new('127.0.0.1', 8502) do |cl|
      cl.with_slave(1) do |slave|
        # Read a single holding register at address 16
        slave.holding_registers[16]

        # Write a single holding register at address 16
        slave.holding_registers[16] = 123

        # Read holding registers 16 through 20
        slave.holding_registers[16..20]

        # Write holding registers 16 through 20 with some values
        slave.holding_registers[16..20] = [1, 2, 3, 4, 5]
      end
    end

for more information see

Conversion to/from 32bit registers

Some modbus devices use two registers to store 32bit values. RModbus provides some helper functions to go back and forth between these two things when reading/writing. The built-in examples assume registers in a particular order but it's trivial to change.

    # Reading values in multiple registers (you can read more than 2 and convert them all so long as they are in multiples of 2)
    res = slave.holding_registers[0..1]
    res.inspect => [20342, 17344]
    res.to_32i => [1136676726]
    res.to_32f => [384.620788574219]

    # Writing 32b values to multiple registers
    cl.holding_registers[0..1] = [1136676726].from_32i
    cl.holding_registers[0..1] => [20342, 17344]
    cl.holding_registers[2..3] = [384.620788574219].from_32f
    cl.holding_registers[2..3] => [20342, 17344]

Support JRuby

Now you could use RModBus on JRuby without RTU implementation.

RTU classes requires gem serialport which currently not compatible with JRuby