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 interpreter runs on the ESP8266 and you can type in commands and read out the results over serial. A serial console cable is perfect for this! Use either an FTDI cable or any console cable, you can use either 3V or 5V logic and power as there is level shifting on the RX pin.
Don't forget to visit esp8266.com for the latest and greatest in ESP8266 news, software and gossip!
Connect USB-Serial cable
Connect either your console cable or FTDI cable. If using FTDI, make sure the black wire goes to the GND (ground) pin
If using a console cable, connect the black wire to ground, red wire to V+, white wire to TX and green wire to RX
You will see the red and blue onboard LED flicker when powered up, but they will not stay lit.
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 115.2kbps 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
Also make sure you have line endings set to CRLF "\r\n" You may also want to turn on inter-character delay if you are pasting in large chunks of code. Each terminal software is different in setting it up, check the manual for the software you're using!
Once the terminal software is connected, click the Reset button on the HUZZAH ESP 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 the board is powered via V+ or Vbat. If they do flicker, make sure you've got the right baud rate selected in the software (9600) and the RX/TX/GND pins connected right
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 first make it an output by typing (not copy & paste)
gpio.mode(3, gpio.OUTPUT)
Turn the LED on by typing (not copy & paste)
gpio.write(3, gpio.LOW)
And off by typing (not copy & paste)
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.
gpio.mode(3, gpio.OUTPUT) 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 it's in a loop, it's not possible to get it to stop via the interpreter. 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've 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,"104.236.193.178") sk:send("GET /testwifi/index.html HTTP/1.1\r\nHost: wifitest.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,"wifitest.adafruit.com") sk:send("GET /testwifi/index.html HTTP/1.1\r\nHost: wifitest.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
Page last edited March 08, 2024
Text editor powered by tinymce.