ESP Arduino Lua

This Arduino library provides the lua 5.3.5 ( release ) scripting engine for ESP32! sketches. This allows dynamic execution of Lua code on the Arduino without having to compile and flash a new firmware. Note modifications from the original library made it uncompilable when esp8266 is used.

Along with the Lua 5.3.5 Core the following Lua standard libraries are included:

• base (print(), tostring(), tonumber(), etc.)
• math
• table (insert(), sort(), remove(), ...)
• string (len(), match(), ...)
• cjson (newly added)
• luaBridge expose class in lua

Prerequisite

• find the platform.txt of the esp32 installation usually found on this path AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.x.x and add this -frtti at the end of this line compiler.cpp.flags.esp32

Sample sketch example: ExecuteScriptFromSerial.ino

After installing the library, some sketch examples are available from the File menu, then Examples and finally under ESP-Arduino-Lua. The examples include ExecuteScriptFromSerial which takes a lua script from the serial line and executes it. As an example, the following standard Arduino functions are available in lua scripts as bindings:

• pinMode()
• digitalWrite()
• delay()
• millis()
• print() (only builtin binding)

# Enter the lua script and press Control-D when finished:
print("My first test!")
# Executing script:
My first test!


# Enter the lua script and press Control-D when finished-
print("Current uptime: " .. millis())
# Executing script:
Current uptime: 159926.0


# Enter the lua script and press Control-D when finished:
print("Hello world!")
# Executing script:
Hello world!


# Enter the lua script and press Control-D when finished:
pinLED = 2
period = 500
pinMode(pinLED, OUTPUT)
while(true)
do
  print("LED on")
  digitalWrite(pinLED, LOW)
  delay(period)
  print("LED off")
  digitalWrite(pinLED, HIGH)
  delay(period)
end
# Executing script:
LED on
LED off

Resources Used (ExecuteScriptFromSerial.ino)

ESP8266: Sketch uses 327776 bytes (31%) of program storage space. Maximum is 1044464 bytes. Global variables use 31276 bytes (38%) of dynamic memory, leaving 50644 bytes for local variables. Maximum is 81920 bytes.

ESP32: Sketch uses 310749 bytes (23%) of program storage space. Maximum is 1310720 bytes. Global variables use 15388 bytes (4%) of dynamic memory, leaving 312292 bytes for local variables. Maximum is 327680 bytes.

Arduino IDE Library example: HelloWorld.ino

#include <LuaWrapper.h>

LuaWrapper lua;

void setup() {
  Serial.begin(115200);
  String script = String("print('Hello world!')");
  Serial.println(lua.Lua_dostring(&script));
}

void loop() {

}

Resources Used (HelloWorld.ino)

ESP8266: Sketch uses 365276 bytes (34%) of program storage space. Maximum is 1044464 bytes. Global variables use 34712 bytes (42%) of dynamic memory, leaving 47208 bytes for local variables. Maximum is 81920 bytes.

ESP32: Sketch uses 309913 bytes (23%) of program storage space. Maximum is 1310720 bytes. Global variables use 15388 bytes (4%) of dynamic memory, leaving 312292 bytes for local variables. Maximum is 327680 bytes.

The Lua Language:

Lua 5.3 Reference Manual