ESP8266 NodeMCU Code

Examples and Demo

• using IDE esplorer can easily manage and program the ESP8266 board
• Here we only try and make sure the code can be compiled well, ds18b20 is not connected.
• Use "upload" to upload code is better for avoiding errors

DS18B20 Read Temperature (simplified codes)

• ds18b20.lua shorten code, this will be used as a lua module

--
-- DS18B20 one wire module for NODEMCU 
-- LICENCE: http://opensource.org/licenses/MIT 
-- Vowstar <vowstar@nodemcu.com> 
-- Dramatic simplification: Peter Scargill 
--

-- Set module name as parameter of require 
local modname = ...
local M = {} 
_G[modname] = M 

--
-- Local used modules 
--
-- Table module 
local table = table 
-- String module 
local string = string 
-- One wire module 
local ow = ow 
-- Timer module 
local tmr = tmr 
-- Limited to local environment 
setfenv(1,M) 
----
-- Implementation – you don’t get any shorter than this 
----

function readNumber(pin) 
        ow.setup(pin) 
        ow.reset(pin) 
        ow.write(pin, 0xCC, 1) 
        ow.write(pin, 0xBE, 1) 
        data = nil 
        data = "" 
        for i = 1, 2 do 
            data = data .. string.char(ow.read(pin)) 
        end 
        t = (data:byte(1) + data:byte(2) * 256) / 16 
        if (t>100) then 
        t=t-4096 
        end 
        ow.reset(pin) 
        ow.write(pin,0xcc,1) 
        ow.write(pin, 0x44,1)   
        return t           
end

-- Return module table 
return M

• Main code file readDS.lua, will use module ds18b20

t=require("ds18b20") 
print("the temperature is  "..t.readNumber(4)) 
t = nil 
ds18b20 = nil 
package.loaded["ds18b20"]=nil

• Init.lua entry, setup wifi and dofile readDS.lua

print(wifi.sta.getip())
wifi.setmode(wifi.STATION)
wifi.sta.config("apname","password")
print(wifi.sta.getip())
dofile('readDS.lua')

HTTP Client

• simple HTTP client

-- A simple http client
conn=net.createConnection(net.TCP, false) 
conn:on("receive", function(conn, pl) print(pl) end)
conn:connect(80,"121.41.33.127")
conn:send("GET / HTTP/1.1\r\nHost: www.nodemcu.com\r\n"
    .."Connection: keep-alive\r\nAccept: */*\r\n\r\n")

More simple HTTP client

-- a simple http server
srv=net.createServer(net.TCP) 
srv:listen(80,function(conn) 
    conn:on("receive",function(conn,payload) 
    print(payload) 
    conn:send("<h1> Hello, NodeMcu.</h1>")
    end) 
end)

PWM operation

function led(r,g,b) 
    pwm.setduty(1,r) 
    pwm.setduty(2,g) 
    pwm.setduty(3,b) 
end
pwm.setup(1,500,512) 
pwm.setup(2,500,512) 
pwm.setup(3,500,512)
pwm.start(1) 
pwm.start(2) 
pwm.start(3)
led(512,0,0) -- red
led(0,0,512) -- blue

Blink LED

lighton=0
tmr.alarm(0,1000,1,function()
if lighton==0 then 
    lighton=1 
    led(512,512,512) 
    -- 512/1024, 50% duty cycle
else 
    lighton=0 
    led(0,0,0) 
end 
end)

repeat using timer

tmr.alarm(1,5000,1,function() print("alarm 1") end)
tmr.alarm(0,1000,1,function() print("alarm 0") end)
tmr.alarm(2,2000,1,function() print("alarm 2") end)
-- after sometime
tmr.stop(0)

Telnet server

-- a simple telnet server
s=net.createServer(net.TCP,180) 
s:listen(2323,function(c) 
    function s_output(str) 
      if(c~=nil) 
        then c:send(str) 
      end 
    end 
    node.output(s_output, 0)   
    -- re-direct output to function s_ouput.
    c:on("receive",function(c,l) 
      node.input(l)           
      --like pcall(loadstring(l)), support multiple separate lines
    end) 
    c:on("disconnection",function(c) 
      node.output(nil)        
      --unregist redirect output function, output goes to serial
    end) 
    print("Welcome to NodeMcu world.")
end)

Read ds18b20

-- read temperature with DS18B20
t=require("ds18b20")
t.setup(9)
addrs=t.addrs()
-- Total DS18B20 numbers, assume it is 2
print(table.getn(addrs))
-- The first DS18B20
print(t.read(addrs[1],t.C))
print(t.read(addrs[1],t.F))
print(t.read(addrs[1],t.K))
-- The second DS18B20
print(t.read(addrs[2],t.C))
print(t.read(addrs[2],t.F))
print(t.read(addrs[2],t.K))
-- Just read
print(t.read())
-- Just read as centigrade
print(t.read(nil,t.C))
-- Don't forget to release it after use
t = nil
ds18b20 = nil
package.loaded["ds18b20"]=nil

• List the code files inside of the board

--list.lua
l = file.list();
    for k,v in pairs(l) do
      print("name:"..k..", size:"..v)
    end

--init.lua will be excuted file.open("init.lua","w") file.writeline(print("Hello World!")) file.close() node.restart() -- this will restart the module.

Basic Init for wifi setup

• Connect wifi

print(wifi.sta.getip())
--nil
wifi.setmode(wifi.STATION)
wifi.sta.config("SSID","password")
print(wifi.sta.getip())
--192.168.18.110

• default init lua, connect to wifi, retrieve IP and then dofile

• init file

--init.lua
print("set up wifi mode")
wifi.setmode(wifi.STATION)
wifi.sta.config("SSID","PassWord")
 --here SSID and PassWord should be modified according your wireless router
wifi.sta.connect()
tmr.alarm(1, 1000, 1, function() 
    if wifi.sta.getip()== nil then 
    	print("IP unavaiable, Waiting...") 
    else 
    	tmr.stop(1)
    	print("Config done, IP is "..wifi.sta.getip())
    	--dofile("yourfile.lua")
    end 
 end)

GPIO control

pin = 1

gpio.mode(pin, gpio.OUTPUT)
gpio.write(pin, gpio.HIGH)

gpio.mode(pin, gpio.INPUT)
print(gpio.read(pin))

• Blink LED or relay

pin = 6
lighton=0

gpio.mode(pin,gpio.OUTPUT)

tmr.alarm(1, 1000, 1, function()
    if lighton==0 then
        lighton=1
        gpio.write(pin,gpio.HIGH)
    else
      lighton=0
      gpio.write(pin,gpio.LOW)
    end
  end)

File operation

• Read config from config.tx

  --MQTT, server, user, password, port
  file.open("config.txt", "r")
  MQTTs = file.readline()
  print("server:"..MQTTs)
  --MQTTs = "m11.cloudmqtt.com"
  MQTTu = file.readline()
  MQTTp = file.readline()
  MQTTpo = file.readline()
  file.close()
  print("server:"..MQTTs)

• the config should represent:

m = net.createConnection(net.TCP, 0)
print("user:"..MQTTu)
m = mqtt.Client(MQTTu, 120, MQTTu, MQTTp)

m:connect(MQTTs, MQTTpo, 0, function(conn) 
        print("connected") 
        m:subscribe("/android/",0, function(conn)
           print("subscribed") 
        end)
     end)

Smartconfig

• Smartconfig for Nodemcu

wifi.setmode(wifi.STATION)

wifi.startsmart(0,
  function(ssid, password)
  print(string.format(“Success. SSID:%s ; PASSWORD:%s”, ssid, password))
  end
)

MQTT

• Client ID can be anything you like, for example Nodemcu_ID1234
• Topic and message is a pair, each topic can have its own message, only the client who subscribe to this topic can receive the message
• You can find the MQTT SPY demo test tool here.
• See how it works below

• 

  Use websocket UI to send and received message

• 

  Use mqttspy to send and received message

Demo Code

• Note to change client_id, username, password, hostname and port below

-- initiate the mqtt client and set keepalive timer to 120sec
mqtt = mqtt.Client("client_id", 120, "username", "password")

mqtt:on("connect", function(con) print ("connected") end)
mqtt:on("offline", function(con) print ("offline") end)

-- on receive message
mqtt:on("message", function(conn, topic, data)
  print(topic .. ":" )
  if data ~= nil then
    print(data)
  end
end)

mqtt:connect("hostname", port, 0, function(conn) 
  print("connected")
  -- subscribe topic with qos = 0
  mqtt:subscribe("my_topic",0, function(conn) 
    -- publish a message with data = my_message, QoS = 0, retain = 0
    mqtt:publish("my_topic","my_message",0,0, function(conn) 
      print("sent") 
    end)
  end)
end)