Sample using Eclipse Mihini and Paho to read modbus values from an Arduino attached to a Raspberry Pi and publish them over MQTT

main.lua

require 'sched'
require 'shell.telnet'

-- Start a telnet server on port 1234
-- Once this program is started , you can start a Lua VM through telnet
-- using the following command: telnet localhost 1234
local function run_server()
  shell.telnet.init {
    address     = '0.0.0.0',
    port        = 1234,
    editmode    = "edit",
    historysize = 100 }
end

local modbus = require 'modbus'
local utils = require("utils")
local MQTT = require("mqtt_library")

local function modbus_processing()
  local config = { baudRate=9600 }

  local modbus_client = modbus.new("/dev/ttyACM0", config, "RTU")
  local mqtt_client = MQTT.client.create("m2m.eclipse.org", "1883")
  mqtt_client:connect("mihini")
  sched.wait(2)

  local led_state = 0

  while true do
		local buffer = modbus_client:readHoldingRegisters(1,0,6)

		local _, rawLight, rawTemp = string.unpack(buffer,"h2")
		print(rawLight)
		mqtt_client:publish("mihini/light", utils.convert(rawLight))
		print(rawTemp)
		print(utils.convert(rawTemp))
		mqtt_client:publish("mihini/temp", utils.convert(rawTemp))
		print('----')
		
		led_state = (led_state + 1) % 2
		modbus_client:writeMultipleRegisters(1,11,string.pack("h1",led_state))
		
		sched.wait(1)
	end
end

local function main()
  -- Create a thread to start the telnet server
  sched.run(run_server)

  sched.run(modbus_processing)

  -- Starting the sched main loop to execute the previous task
  sched.loop()
end

main()