modbus-rtu-master.func16n3.rb

#!/usr/bin/ruby

SERIAL_DEVICE = '/dev/tty.usbserial-FTXYGGG9'
# On Windows, like SERIAL_DEVICE = 'COM5'

require 'rubygems'
require 'rmodbus'
require 'serialport'

# To prepare,
# $ gem environment
# $ gem install -V rmodbus serialport
# To clean-up,
# $ gem uninstall gserver rmodbus serialport

# Serial constants according to the master configuration
BAUD_RATE = 19_200
SERVER_ADDRESS = 50
SERIAL_OPTS = {
  :data_bit => 8,
  :stop_bits => 1,
  :parity => SerialPort::EVEN}
# FYI, default :read_timeout is 100 in SerialPort lib

# Modbus constants

HOLDING_REGISTER_OFFSET = 40001

IDX_WATCHDOG_COUNTER_M2S = 40501 - HOLDING_REGISTER_OFFSET
IDX_WATCHDOG_COUNTER_S2M = 40001 - HOLDING_REGISTER_OFFSET
WATCHDOG_COUNTER_MAX = 2 ** 8
IDX_DATA = 40510 - HOLDING_REGISTER_OFFSET
DATA_COUNTS = 28
INVALID_LENGTH_M2S = -1
LENGTH_S2M = 0x64

# Constants for this implementation
DUMMY_BYTE = 0x00

ModBus::RTUClient.connect(SERIAL_DEVICE, BAUD_RATE, SERIAL_OPTS) do |client|

  client.debug = true

  client.read_retries = Float::INFINITY

  client.with_slave(SERVER_ADDRESS) do |slave|

    time_before = nil
    master_watchdog_counter = -1
    slave_watchdog_counter = nil

    loop do
      time_now = Time.now.utc
      if time_before && time_before.strftime('%s') == time_now.strftime('%s')
        sleep(0.001)
        next
      end
      time_before = time_now

      master_watchdog_counter = (master_watchdog_counter + 1) % WATCHDOG_COUNTER_MAX
      slave.write_multiple_registers(IDX_WATCHDOG_COUNTER_M2S,
                                     [master_watchdog_counter,
                                       Array.new(IDX_DATA - IDX_WATCHDOG_COUNTER_M2S - 1, DUMMY_BYTE),
                                       [time_now.to_a.slice(0, 8),
                                         Array.new(DATA_COUNTS - 8, -1.23456789)].
                                       flatten.collect{|i| [i.to_f].from_32f.reverse}.
                                       flatten[0, DATA_COUNTS * 2 + [INVALID_LENGTH_M2S, 0].sort.first],
                                       if INVALID_LENGTH_M2S > 0
                                         Array.new(INVALID_LENGTH_M2S, DUMMY_BYTE)
                                       else
                                         []
                                       end
                                     ].flatten)
      # Sending s, min, h, day of month, month, year, day of week, day of year and 0
      # for test

      c = slave.read_holding_registers(IDX_WATCHDOG_COUNTER_S2M, LENGTH_S2M).first
      if c == slave_watchdog_counter
        warn "#{time_now.to_s} Received the same watchdog counter: #{slave_watchdog_counter}"
      end
      slave_watchdog_counter = c
      $stderr.puts [time_now.to_s, slave_watchdog_counter].join(',')
    end

  end
end