# NodeMCU Documentation

NodeMCU is an [eLua](http://www.eluaproject.net/) based firmware for the [ESP8266 WiFi SOC from Espressif](http://espressif.com/en/products/esp8266/). The firmware is based on the Espressif NON-OS SDK and uses a file system based on [spiffs](https://github.com/pellepl/spiffs). The code repository consists of 98.1% C-code that glues the thin Lua veneer to the SDK.

The NodeMCU *firmware* is a companion project to the popular [NodeMCU dev kits](https://github.com/nodemcu/nodemcu-devkit-v1.0), ready-made open source development boards with ESP8266-12E chips.

## Programming Model
The NodeMCU programming model is similar to that of [Node.js](https://en.wikipedia.org/wiki/Node.js), only in Lua. It is asynchronous and event-driven. Many functions, therefore, have parameters for callback functions. To give you an idea what a NodeMCU program looks like study the short snippets below. For more extensive examples have a look at the `/lua_examples` folder in the repository on GitHub.

```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)
```
```lua
-- connect to WiFi access point
wifi.setmode(wifi.STATION)
wifi.sta.config("SSID", "password")
```

```lua
-- register event callbacks for WiFi events
wifi.sta.eventMonReg(wifi.STA_CONNECTING, function(previous_state)
	if(previous_state==wifi.STA_GOTIP) then 
	    print("Station lost connection with access point. Attempting to reconnect...")
	else
	    print("STATION_CONNECTING")
	end
end)
```

```lua
-- manipulate hardware like with Arduino
pin = 1
gpio.mode(pin, gpio.OUTPUT)
gpio.write(pin, gpio.HIGH)
print(gpio.read(pin))
```

## Getting Started
1. [Build the firmeware](build.md) with the modules you need.
1. [Flash the firmware](flash.md) to the chip.
1. [Upload code](upload.md) to the firmware.