Lua scripts

Lua scripts#

myGPIOd reads on startup the file defined by the lua_file configuration setting and starts a Lua VM that compiles the file. All lua functions in this file are registered and can be called with the lua action.

Warning

Lua scripts are executed in the main thread, therefore lua scripts can block and terminate it.

Note

The lua functions should not return any value.

Custom lua functions#

myGPIOd registers custom lua functions to provide access to the actions. The functions return true on success, else false as first value.

Lua function

Description

local rc = gpioBlink({GPIO}, {timeout_ms}, {interval_ms})

Toggle the value of the GPIO in given timeout and interval.

local rc, value = gpioGet({GPIO})

Returns the GPIO state: active, inactive or error

local rc = gpioSet({GPIO}, {active|inactive})

Sets the state of an output GPIO.

local rc = gpioToggle({GPIO})

Toggles the state of an output GPIO.

local rc = http({method}, {uri}, {content-type}, {postdata})

Submits a HTTP request in a new child process. Set content-type and postdata to nil if no body should be sent. This is an async function and you can not get the HTTP response. Valid HTTP methods are: DELETE, GET, HEAD, OPTIONS, PATCH, POST, PUT

local rc, value = inputEvGet({device}, {code})

Returns the current value of tracked input event.

local rc = mpc({mpd protocol command})

Runs a mpd protocol command.

local rc = mympd({uri}, {partition}, {script})

Calls the myGPIOd api to execute a script in a new child process. This is an async function and you can not get the HTTP response.

local rc = system({command})

Executes an executable or script in a new child process. This is an async function and you can not get the output of the command.

Example lua file#

This Lua file registers two functions: btnPress and rotaryEncoder.

function btnPress(arg1)
    -- This is printed in the myGPIOd log
    print("btnPress " .. arg1)

    -- HTTP request with no body
    http("GET", "http://nas.lan/btnpress", nil, nil)

    -- myMPD API request to execute a script
    mympd("https://nas.lan/mympd", "default", "test")

    -- Execute a local shell script
    system("/home/juergen/projekte/myGPIOd/etc/command.sh")

    -- Send commands to MPD
    mpc("volume 5")
    mpc("play")

    -- Blink GPIO 3
    gpioBlink(3, 1000, 2000)

    -- Set GPIO 4 to active
    gpioSet(4, "active")

    -- Toggle the state of GPIO 4
    gpioToggle(4)

    -- Get the value of GPIO 1
    local _, val
    _, val = gpioGet(1)
    print("Value of GPIO1: " .. val)
end

-- Add this action to the CLX pin for the rising event
function rotaryEncoder()
  -- Get value of the DT pin
  local _, dt  = gpioGet(6)
  -- Determine rotation direction
  if dt == "active" then
      print("counter-clockwise")
  else
      print("clockwise")
  end
end

-- Check if the left shift key was pressed
function keyPress(key)
  local _, value = inputEvGet("/dev/input/event3", "KEY_LEFTSHIFT")
  if value == 1 then
      print("Left shift key was pressed with key " .. key)
  else
      print("Left shift key was not pressed with key " .. key)
  end
end
Contents