temp-mqtt/application.lua

-- init mqtt client without logins, keepalive timer 120s
m = mqtt.Client("esp", 120)

-- init mqtt client with logins, keepalive timer 120sec
--m = mqtt.Client("", 120, "user", "password")

-- setup Last Will and Testament (optional)
-- Broker will publish a message with qos = 0, retain = 0, data = "offline"
-- to topic "/lwt" if client don't send keepalive packet
--m:lwt("/lwt", "offline", 0, 0)

m:on("connect", function(client) print ("connected") end)
m:on("offline", function(client) print ("offline") end)

-- -- on publish message receive event
-- m:on("message", function(client, topic, data)
--   print(topic .. ":" )
--   if data ~= nil then
--     print(data)
--   end
-- end)

-- Ice-boil calibration
function calibrate(temp)
   local ReferenceLow = 0.01
   local ReferenceHigh = 100
   local ReferenceRange = ReferenceHigh - ReferenceLow
   local RawLow = TEMP_ICE
   local RawHigh = TEMP_BOIL
   local RawRange = RawHigh - RawLow
   local RawValue = temp
   local CorrectedValue = (((RawValue - RawLow) * ReferenceRange) / RawRange) + ReferenceLow

   if RawLow == nil or RawHigh == nil then
      return temp
   end

   return CorrectedValue
end

local ow_pin = TEMP_PIN
ds18b20.setup(ow_pin)

function ds_start_read()
   ds18b20.read(
      function(ind,rom,res,raw_temp,tdec,par)
         local mac = string.format("%02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X",string.match(rom,"(%d+):(%d+):(%d+):(%d+):(%d+):(%d+):(%d+):(%d+)"))
         local temp = calibrate(raw_temp)
         print(ind,mac,res,temp,raw_temp)
         ok, json = pcall(sjson.encode, {rom=mac, res=res, temp=temp, raw=raw_temp})
         if ok then
            m:publish(MQTT_TOPIC, json, 0, 0, function(client) print("sent "..json.." to "..MQTT_TOPIC) end)
         else
            print("failed to encode!")
         end
    end,{});
end

function handle_mqtt_connected(client)
  print("mqtt connected")
  -- subscribe topic with qos = 0
  -- client:subscribe(MQTT_TOPIC, 0, function(client) print("subscribe success") end)
  -- publish a message with data = hello, QoS = 0, retain = 0
  -- client:publish("/topic", "hello", 0, 0, function(client) print("sent") end)

  -- start temp reading
  ds_start_read()
  tmr.create():alarm(TEMP_RATE, tmr.ALARM_AUTO, function(timer) ds_start_read() end)
end

function handle_mqtt_error(client, reason)
  tmr.create():alarm(10 * 1000, tmr.ALARM_SINGLE, do_mqtt_connect)
end

function do_mqtt_connect()
  m:connect(MQTT_SERVER, handle_mqtt_connected, handle_mqtt_error)
end

do_mqtt_connect()