# **NodeMCU 2.2.1** #
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### A Lua based firmware for ESP8266 WiFi SOC
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 2.2.1](https://github.com/espressif/ESP8266_NONOS_SDK/releases/tag/v2.2.1) 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.
# Summary
- Easy to program wireless node and/or access point
- Based on Lua 5.1.4 (without *debug, os* modules)
- Asynchronous event-driven programming model
- more than 65 built-in modules
- Firmware available with or without floating point support (integer-only uses less memory)
- Up-to-date documentation at [https://nodemcu.readthedocs.io](https://nodemcu.readthedocs.io)
# 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`](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(sck, payload)
print(payload)
sck:send("HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n Hello, NodeMCU.
")
end)
conn:on("sent", function(sck) sck:close() end)
end)
```
```lua
-- connect to WiFi access point
wifi.setmode(wifi.STATION)
wifi.sta.config{ssid="SSID", pwd="password"}
```
# Documentation
The entire [NodeMCU documentation](https://nodemcu.readthedocs.io) is maintained right in this repository at [/docs](docs). The fact that the API documentation is maintained in the same repository as the code that *provides* the API ensures consistency between the two. With every commit the documentation is rebuilt by Read the Docs and thus transformed from terse Markdown into a nicely browsable HTML site at [https://nodemcu.readthedocs.io](https://nodemcu.readthedocs.io).
- How to [build the firmware](https://nodemcu.readthedocs.io/en/master/en/build/)
- How to [flash the firmware](https://nodemcu.readthedocs.io/en/master/en/flash/)
- How to [upload code and NodeMCU IDEs](https://nodemcu.readthedocs.io/en/master/en/upload/)
- API documentation for every module
# Releases
Due to the ever-growing number of modules available within NodeMCU, pre-built binaries are no longer made available. Use the automated [custom firmware build service](http://nodemcu-build.com/) to get the specific firmware configuration you need, or consult the [documentation](http://nodemcu.readthedocs.io/en/master/en/build/) for other options to build your own firmware.
This project uses two main branches, `master` and `dev`. `dev` is actively worked on and it's also where PRs should be created against. `master` thus can be considered "stable" even though there are no automated regression tests. The goal is to merge back to `master` roughly every 2 months. Depending on the current "heat" (issues, PRs) we accept changes to `dev` for 5-6 weeks and then hold back for 2-3 weeks before the next snap is completed.
A new tag is created every time `dev` is merged back to `master`. They are listed in the [releases section here on GitHub](https://github.com/nodemcu/nodemcu-firmware/releases). Tag names follow the \-master_yyyymmdd pattern.
# Support
See [https://nodemcu.readthedocs.io/en/master/en/support/](https://nodemcu.readthedocs.io/en/master/en/support/).
# License
[MIT](https://github.com/nodemcu/nodemcu-firmware/blob/master/LICENSE) © [zeroday](https://github.com/NodeMCU)/[nodemcu.com](http://nodemcu.com/index_en.html)