if true then
		print("set up wifi mode")
		wifi.setmode(wifi.STATION)
		wifi.sta.config("wifi","pwd")
		wifi.sta.connect()
		
		local cnt = 0
		tmr.alarm(1, 1000, 1, function() 
			if (wifi.sta.getip() == nil) and (cnt < 20) then 
				print("IP unavaiable, Waiting...")
				cnt = cnt + 1 
			else 
				tmr.stop(1)
				tmr.unregister(1)
				if (cnt < 20) then 
				  print("Config done, IP is "..wifi.sta.getip())
				  --dofile("try_dht.lua")
				else 
				  print("Wifi setup time more than 20s, Please verify wifi.sta.config() function. Then re-download the file.")
				end
			end 
		 end)
	else
		print("\nPlease edit 'init.lua' first:")
	end

	local moduleName = ...
	local M = {}
	_G[moduleName] = M

	local device = ""
	local apikey = ""

	function M.init(_device, _apikey)
	  device = tostring(_device)
	  apikey = _apikey
	end

	function M.addDatapoint(sensor, datapoint, callback)
	  if datapoint == nil or sensor == nil then
		return
	  end

	  local sk=net.createConnection(net.TCP, 0)

	  sk:on("connection", function(conn)
		print("connect yeelink OK...")

		local content = "POST /v1.0/device/"..device.."/sensor/"..sensor.."/datapoints HTTP/1.1\r\n"
		  .."Host: api.yeelink.net\r\n"
		  .."Content-Length: "..string.len(datapoint).."\r\n"--the length of json is important
		  .."Content-Type: application/x-www-form-urlencoded\r\n"
		  .."U-ApiKey:"..apikey.."\r\n"
		  .."Cache-Control: no-cache\r\n\r\n"
		  ..datapoint.."\r\n"

		sk:send(content)

	  end)

	  sk:on("receive", function(sck,c)
		  if callback ~= nil then
			callback()
		  end
		  
		  sk:close();
		  sk=nil;
	  end)

	  sk:connect(80,"api.yeelink.net")

	end

	return M