require "rmodbus"
require "ccutrer-serialport"

value = ARGV[0]&.to_i

ModBus::RTUClient.new("/dev/ttyUSB0", 9600) do |cl|
  cl.with_slave(7) do |slave|
    regs = slave.holding_registers
    regs[2] = value
    sleep 0.1
  end
end