Using NodeMCU Lua

Each Feather HUZZAH ESP8266 breakout comes pre-programmed with NodeMCU's Lua interpretter. As of this writing, we ship with NodeMCU 0.9.5 build 20150318  powered by Lua 5.1.4 but it may be more recent

Lua is still a work in progress, so we strongly recommend visiting NodeMCU and updating your Lua version to the very latest as they have the ability to make you the latest continuous build. Then follow their guide on how to update Lua!

The Lua interpretter runs on the ESP8266 and you can type in commands and read out the results over serial. In order to upload code to the ESP8266 and use the serial console, connect any data-capable micro USB cable to the Feather HUZZAH and the other side to your computer's USB port. Install the required CP2104 USB driver to have the COM/Serial port appear properly

Don't forget to visit esp8266.com for the latest and greatest in ESP8266 news, software and gossip!

Don't forget to install the USB driver for the CP2104 USB-to-Serial chip!

Open up serial console

Next up, on your computer, use a serial console program such as CoolTerm (Mac) or Putty (Windows) or screen (linux). Teraterm seems to dislike the initial 74400bps data stream from the ESP8266 so you can try it but you'll possibly need to reset the terminal software.

  • Connect up to the COM or Serial port used by your cable, at 9600 Baud
  • Make sure you have turned off any hardware handshake or flow control
  • Putty isn't good with pasting code in, so you may not be able to copy-n-paste!
  •  Also make sure you have line endings set to CRLF "\r\n"

Use any serial console program you like, we just happen to be used to Putty!

Once the terminal software is connected, click the Reset button on the Feather HUZZAH ESP8266 board to reset it and have it print out the welcome message:

If you don't get this message, first check that the red/blue leds flickered when you press the reset button. If they didnt, make sure you've got the right baud rate selected in the software (9600)

Hello world!

Ok we can now turn on an LED. There is a red LED on each board, connected to GPIO #0

NodeMCU Lua's pinouts are not the same as the Arduino/gcc pinouts. We print the Arduino pinouts on the board so watch out!
The Lua documentation for the ESP8266 has GPIO #4 and #5 swapped so if #4/#5 aren't working for you, try swapping!

Pin Notes

PCB/Arduino

NodeMCU/Lua

No pullups!

0

3

2

4

3

9

4

1

5

2

9

11

10

12

12

6

13

7

14

5

15

8

16

0

So to set the pin #0 LED on and off (which would be pin #3 in Lua) first make it an output:

gpio.mode(3, gpio.OUTPUT)

Turn the LED on with:

gpio.write(3, gpio.LOW)

And off with:

gpio.write(3, gpio.HIGH)

You can make this a little more automated by running a longer script.

For longer text, pasting can be difficult as the lua interpreter needs a little delay time between characters and also require CR-LF settings. For that reason you may want to paste each line and then hit return manually.

while 1 do
  gpio.write(3, gpio.HIGH)
  tmr.delay(1000000)   -- wait 1,000,000 us = 1 second
  gpio.write(3, gpio.LOW)
  tmr.delay(1000000)   -- wait 1,000,000 us = 1 second
end

The LED will now be blinking on and off.

Note that since its in a loop, its not possible to get it to stop via the interpretter. To stop it, click the Reset button again!

This code halts the processor during the tmr.delay, a smarter way to blink an LED is to use the timer capability to set off the LED control (code from here)

-- Pin definition 
local pin = 3
local status = gpio.LOW
local duration = 1000    -- 1 second duration for timer

-- Initialising pin
gpio.mode(pin, gpio.OUTPUT)
gpio.write(pin, status)

-- Create an interval
tmr.alarm(0, duration, 1, function ()
    if status == gpio.LOW then
        status = gpio.HIGH
    else
        status = gpio.LOW
    end

    gpio.write(pin, status)
end)

Scanning & Connecting to WiFi

We'll continue with a quick demo of scanning for WiFi and connecting.

Once you're back at the Lua prompt, set the ESP8266 into WiFi Client mode with

wifi.setmode(wifi.STATION)

Then you can run the scanner and have it print out the available AP's

-- print ap list
function listap(t)
      for k,v in pairs(t) do
        print(k.." : "..v)
      end
end
wifi.sta.getap(listap)

or for more detail...

-- print ap list
function listap(t)
      for ssid,v in pairs(t) do
        authmode, rssi, bssid, channel = string.match(v, "(%d),(-?%d+),(%x%x:%x%x:%x%x:%x%x:%x%x:%x%x),(%d+)")
        print(ssid,authmode,rssi,bssid,channel)
      end
end
      
wifi.sta.getap(listap)

We can connect to the access point with wifi.sta.config and wifi.sta.connect - it will take a second or two to complete the connection, you can query the module to ask the status with wifi.sta.status() - when you get a 5 it means the connection is completed and DHCP successful

wifi.sta.config("accesspointname","yourpassword")
wifi.sta.connect()
tmr.delay(1000000)   -- wait 1,000,000 us = 1 second
print(wifi.sta.status())
print(wifi.sta.getip())

WebClient example

Once you're got the IP address you can connect to adafruit, for example, and read a webpage and print it out:

sk=net.createConnection(net.TCP, 0)
sk:on("receive", function(sck, c) print(c) end )
sk:connect(80,"207.58.139.247")
sk:send("GET /testwifi/index.html HTTP/1.1\r\nHost: www.adafruit.com\r\nConnection: keep-alive\r\nAccept: */*\r\n\r\n")

You can also have the module do DNS for you, just give it the hostname instead of IP address:

sk=net.createConnection(net.TCP, 0)
sk:on("receive", function(sck, c) print(c) end )
sk:connect(80,"www.adafruit.com")
sk:send("GET /testwifi/index.html HTTP/1.1\r\nHost: www.adafruit.com\r\nConnection: keep-alive\r\nAccept: */*\r\n\r\n")

This is just a light overview of testing out your HUZZAH ESP breakout! For much more, check out NodeMCU's documentation page https://nodemcu.readthedocs.io/ for the details on what functions are available to you, as well as  http://www.lua.org to learn more about the Lua scripting language

Last updated on 2017-06-02 at 11.15.39 AM Published on 2015-11-25 at 03.07.09 PM