NodeMCU

**NodeMCU**是一个开源的物联网平台。 它使用Lua脚本语言编程。该平台基于eLua 开源项目,底层使用ESP8266 sdk 0.9.5版本。该平台使用了很多开源项目, 例如 lua-cjson, spiffs. NodeMCU包含了可以运行在 esp8266 Wi-Fi SoC芯片之上的固件,以及基于ESP-12模组的硬件。

## History
NodeMCU is started after ESP8266 come out. In December 30, 2013, Espressif systems begin production of ESP8266. ESP8266 is an Wi-Fi SoC and integrated with LX106 core, widely used in IoT applications(See related projects). In 13 Oct 2014, Hong committed first file of nodemcu-firmware to github, NodeMCU project started. And then more and more developers from ESP8266 opensource community join in NodeMCU developer team. On 1 Dec 2014, Huang R commit the gerber file of an ESP8266 board, then NodeMCU project have the first open-hardware which named devkit 1.0, thus NodeMCU is not only a firmware, it becomes a platform. In 31 Dec 2014, Tuan PM port MQTT client library from Contiki to ESP8266 SoC platform, and commit to NodeMCU project, then NodeMCU can support MQTT IoT protocol, using Lua access MQTT broker, it is an important update of firmware. Another important update is in 30 Jan 2015, Devsaurus port u8glib to NodeMCU project, and NodeMCU can drive LCD, Screen, OLED, even VGA display module easily.

## Pins腳
NodeMCU 提供對 GPIO（通用輸入/輸出）的存取控制，並且引腳映射表是 API 文件的一部分。    

[*] D0 (GPIO16) 只能用於GPIO讀/寫。它不支援open-drain/interrupt/PWM/I²C 或 1-Wire。

## 硬體連接
如果使用 NodeMCU devkit, 只需要安裝 CH340G 驅動程式, 並且將開發模組使用micro-usb 線連接到電腦。 然後，將波特率設為9600, 並打開序列埠。若使用普通的esp8266模组, 則必須準備usb-ttl 轉接器。

## 固件烧写
nodemcu_latest.bin: 0x00000 对于大多数 esp8266 模块, 直接拉低 GPIO0 引脚的电平，并且重新上电或重启。 可以使用 nodemcu-flasher 烧写固件。

特别的，如果你想编译/构建自己的固件，需要注意以下烧写地址： 0x00000.bin: 0x00000 0x10000.bin: 0x10000

注意，*在烧写之后，最好执行 file.format() *

## 程式举例
### 连接Wi-Fi热点


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

### 如同[[arduino]]般操作硬体


```lua
pin = 1
    gpio.mode(pin,gpio.OUTPUT)
    gpio.write(pin,gpio.HIGH)
    print(gpio.read(pin))
```

### 使用 nodejs 风格网络编程


```lua
-- A simple http client
    conn=net.createConnection(net.TCP, 0)
    conn:on("receive", function(conn, payload) print(payload) end )
    conn:connect(80,"115.239.210.27")
    conn:send("GET / HTTP/1.1\r\nHost: www.baidu.com\r\n"
        .."Connection: keep-alive\r\nAccept: */*\r\n\r\n")
```

### 简易的HTTP伺服器


```lua
-- 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)
      conn:on("sent",function(conn) conn:close() end)
    end)
```

### 连接 MQTT Broker


```lua
-- init mqtt client with keepalive timer 120sec
m = mqtt.Client("clientid", 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(con) print ("connected") end)
m:on("offline", function(con) print ("offline") end)

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

-- for secure: m:connect("192.168.11.118", 1880, 1)
m:connect("192.168.11.118", 1880, 0, function(conn) print("connected") end)

-- subscribe topic with qos = 0
m:subscribe("/topic",0, function(conn) print("subscribe success") end)
-- or subscribe multiple topic (topic/0, qos = 0; topic/1, qos = 1; topic2 , qos = 2)
-- m:subscribe({["topic/0"]=0,["topic/1"]=1,topic2=2}, function(conn) print("subscribe success") end)
-- publish a message with data = hello, QoS = 0, retain = 0
m:publish("/topic","hello",0,0, function(conn) print("sent") end)

m:close();
-- you can call m:connect again
```

### UDP 客户端与伺服器


```lua
-- a udp server
s=net.createServer(net.UDP)
s:on("receive",function(s,c) print(c) end)
s:listen(5683)

-- a udp client
cu=net.createConnection(net.UDP)
cu:on("receive",function(cu,c) print(c) end)
cu:connect(5683,"192.168.18.101")
cu:send("hello")
```


## 引用文献