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2.7 EdgeTX 2.7 Lua Reference Guide

The latest version of this guide will always be available here. At the top of the left sidebar there is a version option if you are running an older version of EdgeTX and need the docs for that specific version.

Please feel free to make suggestions or corrections to the documentation on GitHub, but the preferred method of editing is to use GitBook, so all changes will need to be made by someone who is authorized as a writer there.

This guide covers the development of user-written scripts for R/C transmitters running the EdgeTX 2.7 operating system with Lua support. Readers should be familiar with EdgeTX, the EdgeTX Companion, and know how to transfer files the SD card in the transmitter.

If you are new to Lua programming, you may also find the Lua Reference Manual of assistance.

Part I is an overview of the different script types, along with basic examples of each.

Part II is a programming guide that introduces the types of EdgeTX Lua scripts and how to use them.

Part III is the EdgeTX Lua API Reference

Part IV covers advanced topics with examples

Introduction

This section includes Acknowledgments and Getting Started.

Acknowledgments

The EdgeTX team has no intention of making a profit from their work - EdgeTX is free and open source and will remain free and open source. However, the project is more expensive to maintain than most open source projects. This in mainly because there is a never ending flood of hardware to integrate and maintain code for. Hardware that costs. In addition, in order to develop for this hardware, certain specalised test and measurement equipment is also required.

In order to support this, EdgeTX has chosen to use OpenCollective to allow for donations from the community, as well as funding from manufacturers who choose to partner with and sponsor the project. This also allows for transparent accounting of what the funds are spent on.

Please visit our OpenCollective page if you would like to financially help support the project!

Getting Started

Downloading EdgeTX Companion

EdgeTX Companion 2.7 is available for download here (pick the appropriate download for your operating system from Assets heading at the bottom of the page - the filename will have cpn in the name).

Enabling support for Mixer Scripts

If you intend to use mixer scripts, when compiling the firmware for your transmitter you need to make sure the LUA_MIXER option is set. This is not required if you only intend to run any of the other types of Lua script (i.e. telemetry, one-time, function scripts, widgets) as support for those is included by default.

Part I - Script Type Overview

This section introduces the types of Lua scripts supported by EdgeTX and how they may be used.

Custom (Mixer) Scripts

WARNING - Do not use Lua Custom scripts for controlling any aspect of your model that could cause a crash if the script stops executing!

Overview

Each model can have several custom scripts associated with it, and these scripts are run periodically. They behave similarly to standard OpenTX mixers, but at the same time they provide a much more flexible and powerful tool. Custom scripts take one or more values as inputs, do some processing in Lua code, and output one or more values.

Please note: the firmware must be compiled with the option LUA_MIXER=Y for Custom scripts to be available.

Please note: the scripts should be as short as possible, to avoid delays. It is also important to keep in mind that other loaded Telemetry and Function scripts can add to the response time, or worse: hang the system!

Typical uses

replacement for complex mixes that are not critical to model function
complex processing of inputs and reaction to their current state and/or their history
filtering of telemetry values

Limitations

cannot update LCD screen or perform user input.
should not exceed allowed run-time/ number of instructions.
custom scripts are run with less priority than built-in mixes. Their execution period is around 30ms and is not guaranteed!
can be disabled/killed anytime due to logic errors in script, not enough free memory, etc...)

Lifetime

Custom scripts are loaded from SD card when model is selected
init __function is called first
run function is called periodically (about 30 times per second)
the script is killed (stopped and disabled) if it misbehaves (e.g. run-time error or low memory)
all Custom scripts are stopped while a One-Time script is running (see Lua One-time scripts)

Disabled script

If the script output is used as a mixer source , and the script is killed for whatever reason, then the whole mixer line is disabled ! This can be used for example to provide a fallback in case Lua Custom script is killed.

Example where Lua mix script is used to drive ailerons in some clever way, but control falls back to the standard aileron mix if script is killed. Second mixer line replaces the first one when the script is alive:

CH1  [I4]Ail Weight(+100%)
  := LUA4b Weight(+100%)

File Location

Place them on SD card in folder /SCRIPTS/MIXES/. File name length (without extension) must be 6 characters or less (this limit was 8 characters in OpenTX 2.1).

Interface

Every script must include a return statement at the end, defining its interface to EdgeTX. This statement returns a table with the following fields:

input table (optional)
output table (optional)
init function (optional)
run function

Example

local input =
  {
    { "Strength", SOURCE},           -- user selects source (typically slider or knob)
    { "Interval", VALUE, 0, 100, 0 } -- interval value, default = 0.
  }

local output = { "Val1", "Val2" }

local function init()
  -- Called once when the script is loaded
end

local function run(Strength, Interval) -- Must match input table
  local v1, v2
  -- Called periodically
  return v1, v2                        -- Must match output table
end

return { input=input, output=output, run=run, init=init }

Input table

The input table defines what values are available as input(s) to custom scripts. There are two forms of input table entries.

{ "<name>", SOURCE }

SOURCE inputs provide the current value of a selected OpenTX variable. The source must be selected by the user when the script is configured. Source can be any value that EdgeTX knows about (inputs, channels, telemetry values, switches, custom functions etc.). Note: the typical input range is -1024 thru +1024. Simply divide the input value by 10.24 to convert to a percentage from -100% to +100%.

{ "<name>", VALUE, <min>, <max>, <default> }

VALUE inputs provide a constant value that is set by the user when the script is configured.

name - maximum length of 8 characters
min - minimum value of -128
max - maximum value of 127
default - must be within the valid range specified
Maximum of 6 inputs per script (was 8 in 2.1)

Output table

The output table defines only name(s), as the actual values are returned by the script's run function.

{ "<name1>", "<name2>" }

Note: the above names are only visible as source values on the radio screen when the script is running. If the model is edited in Companion, then the values show as LUA1a and LUA1b etc.

One-Time Scripts

WARNING - Running a One-Time script will suspend execution of all other currently loaded Lua scripts (Custom, Telemetry, and Functions)

Overview

One-Time scripts start when called upon by a specific radio function or when the user selects them from a contextual menu. They do their task and are then terminated and unloaded. Please note that all persistent scripts are halted during the execution of One-Time scripts. They are automatically restarted once the One-Time script is finished. This is done to provide enough system resources to execute the One-Time script.

Lifetime

Script is executed when user selects Execute on a script file from SD card browser screen, or opens a Lua Tool, or creates a new model with a Wizard script.

The script executes until:

it returns value different from 0
is forcefully closed by user by long press of EXIT key
is forcefully closed by system if it misbehaves (e.g. run-time error or low
memory)

File Location

General One-Time scripts can be placed anywhere on SD card, however, the folder /SCRIPTS/ is recommended.

Tool scripts must be stored in /SCRIPTS/TOOLS.

Wizard scripts must be stored in the same subfolder of /TEMPLATES/ with the same "first name" as the template file using it. Some Wizard scripts are just small scripts that load one of the common scripts located in /SCRIPTS/WIZARD/.

Interface

Every script must include a return statement at the end, defining its interface to EdgeTX. This statement returns a table with the following fields:

init function (optional)
run function

Example

Notes:

A non-zero return value from run will halt the script. If the return value is a text string with the file path to a new Lua script, then the new script will be loaded and run.

Function Scripts

Overview

Function scripts are invoked via the 'Lua Script' option of Special Functions configuration page.

Typical uses of Function scripts are:

specialized handling in response to switch position changes
customized announcements

Please be aware that:

all function scripts are stopped if a One-Time Lua script is running
Function scripts DO NOT HAVE ACCESS TO LCD DISPLAY

Lifetime

init function is called once when the model is selected
depending on the switch associated with the Special Function, either the run function (switch = on) or the background function (switch = off) is called periodically
the script is stopped and disabled if it misbehaves (e.g. run-time error or low memory)

File Location

Scripts are located on the SD card in the folder /SCRIPTS/FUNCTIONS/<name>.lua. File name length (without extension) must be 6 characters or less (this limit was 8 characters in OpenTX 2.1).

Interface

Every script must include a return statement at the end, defining its interface to EdgeTX. This statement returns a table with the following fields:

init function (optional)
run function
background function (optional)

Example

local function init()
  -- Called once when the script is loaded
end

local function run()
  -- Called periodically while the Special Function switch is on
end

local function background()
  -- Called periodically while the Special Function switch is off
end

return { run=run, background=background, init=init }

Widget Scripts

Overview

Most of the time, widget scripts show some info in a zone either in the top bar or in one of the user defined main views, and they cannot receive direct input from the user via key events like e.g. Telemetry scripts.

But widgets on the main views can also be shown in full screen mode, where they take over the entire screen area. And here they receive user input via key events, and for radios with touch screen, also touch events. Full screen mode can be entered by selecting the widget, pressing ENTER and selecting Full screen on the widget menu, or by double tapping the widget on radios with a touch screen. Full screen mode can be exited by long pressing the RETURN button, or by calling the Lua function lcd.exitFullScreen().

Each model can have up to five main views, with up to 8 widgets per screen, depending on their size and layout. Each instance of a widget has his own options table.

Please note: Widget scripts are only available on radios with color screens, e.g. FrSky Horus models, Radiomaster TX16 and Jumper T16.

Lifetime

All widget scripts on the SD card are loaded into memory when the model is selected; even widgets that are not used. This has the side effect that any global functions defined in a widget script will always be available to other widget scripts. It also means that any script on the SD card will consume part of the radio's memory - even if it is not being used. Therefore, it is important to either keep widget scripts small, or to use Lua's loadScript() function to load code dynamically.

They can be added to the top bar or a main view through the telemetry setup menu. When a widget has been added to a screen, then the widget functions are called as follows:

create is called once when the widget instance is registered (started).
update is called when widget settings are changed by the user.
background is called periodically when the widget instance is not visible. Note: this is different from the way that telemetry scripts are handled.
refresh is called periodically when the widget instance is visible. Note: if you want background to run when the widget is visible, then call it from refresh.
A widget script is stopped and disabled if it misbehaves (e.g. too long runtime, run-time error, or low memory)
All widgets are stopped while a One-Time script is running (see ).

File Location

Widgets are located on the SD card, each in their specific folder /WIDGETS/<name>/main.lua (<name> must be in 8 characters or less).

Interface

Every script must include a return statement at the end, defining its interface to EdgeTX. This statement returns a table with the following fields:

name string
options table
create function
update function
background function (optional)
refresh function

Example

Notes

The name must be max. 10 characters long.
options is passed to create and then stored in Lua. Changing it has no effect on EdgeTX.
If options is changed by the user in the Widget Settings menu, then update will be called with a new options table, unaffected by any changes made by Lua code to the old options table.
Maximum five options are allowed, with names of max. 10 characters, and no spaces.
If local variables are declared outside functions in the widget script, then they are shared between all instances of the widget.
Therefore, local variables that are private for each instance should be added to the widget table in the create function before returning the widget table to EdgeTX.
When the widget is not in full screen mode, then both event and touchState are nil.
The size of the widget's screen area is as follows:
- Full screen mode: LCD_W by LCD_H
- Not full screen mode: zone.w by zone.h

Part II - EdgeTX Lua API Programming Guide

This section provides more specifics on the EdgeTX Lua implementation. Here you will find syntax rules for interface tables and functions.

Lua Basics

Lua is a small but powerful language. This section will explain a few of the most important concepts.

Introduction

Lua was chosen for OpenTX, and hence also EdgeTX, because it is a small language designed to be highly extensible by libraries written in C and C++, so it can be integrated into other systems like EdgeTX. It is also relatively efficient, both in terms of memory and CPU usage, and hence well suited for the radios.

In addition to the provided libraries, Lua has a very elegant mechanism for loading new Lua code modules during run-time. A lot of the elegance comes from the way that the loading mechanism meshes with another concept supported by Lua: first class functions with closures.

First Class Functions

Computer science pioneer Christopher Strachey introduced the concept of functions as first-class objects in his paper from 1967. What it means is that functions can be treated as other variables: as arguments passed in function calls, as results returned from function calls, and a function identifier can be re-assigned to another chunk of function code, just like a variable ca be assigned to a new value.

In Lua, a function declaration is really "syntactic sugar" for assigning a variable to the chunk of code that is called when the function is invoked, i.e.

local function f(x) return x + 1 end

is the same as

local f = function(x) return x + 1 end

You can even add functions to Lua tables, i.e.

t = { f = f }

will add the above function to the table t, as a field that is also called f. Does that look familiar to the return statement required at the end of a Lua script?

Yes indeed, because a script is really an anonymous function that returns a list of functions to the system. The function declarations assign variables to chunks of function code, these variables are added to the list returned at the end of the script, and the system then calls the functions periodically to run the script. So the script itself is run one time initially, and subsequently the functions returned by the last statement are called periodically.

Closures

Another important concept that goes with first-class functions, is closures. This is the environment of the function with the variable names that the function can see. Please consider the following function counter that returns another function:

The function is returned directly without being assigned to a variable name. The closure of the function returned is the body of the function counter, containing both the arguments start and step, and the local variable x. So if c1 = counter(1, 1) then c1() will return 1, 2, 3, ... when called repeatedly, and if c2 = counter(2, 3) then c2() will return 2, 5, 8, ...

Likewise, the local variables that you declare outside the functions of your script can be used by all of the functions in your script, and they persist between function calls, but they are not visible to other scripts.

Functions with Variable Number of Arguments

Please consider this function:

if event == EVT_VIRTUAL_ENTER or event == EVT_VIRTUAL_EXIT then

can be replaced by

if match(event, EVT_VIRTUAL_ENTER, EVT_VIRTUAL_EXIT) then

You can also use ... directly as a comma separated list of values, e.g. local a, b, c = ... will assign the three variables to the three first arguments following x, or nil if none are given.

References

Loading Code Modules Dynamically

Lua makes it easy to load and unload code modules on the fly, to save memory or to provide program extensions.

The function will load a script from a the file and return a function that is the body of the script, as described in the previous section. So you could have the following Lua script file saved on the SD card:

You can load and use the above file with the following code:

So here we put together what we learned in the previous section. The body of the script is an anonymous function returned by loadScript and stored in the variable chunk. It returns the function f when it is called. The local variable c in the script is assigned to the first vararg passed to the call. Since a new closure is created every time we call chunk, f1 and f2 have different closures with different values of c.

Saving Memory

This chapter will show you some ways that large script projects can be fitted into the limited memory of our radios.

Regarding memory, the situation is a bit different for the radios with black/white or grey scale screens and telemetry scripts, and the radios with color screens and widget scripts. The telemetry script radios only have 128-192 KB RAM memory - that is very small! The widget script radios have 8 MB RAM memory. But the way that widgets are designed means that all widget scripts present on the SD card will be loaded into memory, whether or not they are actually used. Therefore, different strategies should be applied to save memory for the two different types of radios and scripts.

Telemetry Script Radios

Radios with black/white or grey scale screens and telemetry scripts such as e.g. FrSky Taranis, Xlite, Jumper T12 and Radiomaster TX12 have extremely small RAM memories, and therefore it may be necessary to divide up your script into smaller loadable modules.

The following simple example demonstrates how different screens can be loaded on demand, and how shared data can be stored in a table.

The table shared contains data that is shared between the main telemetry script and the loadable screens. Notice that the functions shared.changeScreen and shared.run are also shared this way.

Code is loaded by shared.changeScreen with the loadScript function, which returns the loadable script as a chunk of code. The code is executed with shared as the argument, and the loadable script adds a new run function to the shared table. shared.run is called by run in the main script.

Radios with color screens and widget scripts such as e.g. FrSky Horus, Jumper T16 and Radiomaster TX16S have fairly large RAM memories, but since all widget scripts present on the SD card are always loaded into memory, they could run out of memory if many big widget scripts are present on the card - even if they are not being used by the selected model. Therefore, large widget scripts should be divided into a small main script and a large loadable part. One way to accomplish this is the following.

Obviously, the bulk of the widget's code goes in loadable.lua, and is only loaded if the widgets is in fact being used. Therefore, if the widget is not used, only the small amount of code in main.lua is loaded into the radio's memory.

For an example of a widget that uses the above design pattern, please have a look at the EventDemo widget that is included on the SD card with EdgeTX for color screen radios.

Using Key and Touch Events

This section will discuss how interactive scripts receiving user inputs via key and touch events can be created.

The two Lua widgets EventDemo and LibGUI are provided on the SD card content for color screen radios. EventDemo is just a small widget showing off how key, and especially touch events, can be used. LibGUI contains a globally available library, and a widget showing how the library can be used by other widgets. This section will discuss these two widgets for color screen radios, but generally, what is stated about key events here also applies to the run function in Telemetry and One-Time scripts.

This widget uses the design pattern for saving memory by loadable files discussed in the so all of the action takes place in the file loadable.lua. The following code listing is an outline of the refresh function with comments explaining what is going on.

LibGUI

LibGUI was created to support the SoarETX widgets, but it was made separate so everyone can use it, if they so desire. Since it is all Lua, the code is visible for everyone to study and use as is, or modify for their own use (as long as they comply with the terms of the Gnu Public license, of course).

It is a widget that comes with a global library. Since all widgets are loaded, whether or not they are being used, global functions declared in the body of a widget script will always be available in any widget script in the create and refresh functions. It is not necessary to setup the widget to use the library, and the only purpose of the widget is to show how LibGUI can be used to create widget apps.

The global function loadGUI() returns a new libGUI object. This object can be used to create new GUIobjects, which are used to create screens with elements like buttons, menus, labels, numbers etc.

libGUI Properties

libGUI has the following properties controlling general settings for the library.

libGUI.flags

These are default drawing flags to be applied if no flags are given at creation of screen elements.

Note: these flags should not contain color values, as colors are added by the following.

libGUI.colors

This is a table of the colors used for drawing the GUI elements. These are all theme colors by default, but they can be changed for the libGUI instance without changing the theme colors anywhere else.

libGUI.widgetRefresh

A function f() to draw the zone of the screen in widget mode. It takes no arguments.

libGUI Functions

libGUI.match(x, ...)

This is a small utility function that returns true if the first argument x matches any of the following arguments. It is useful for comparing values of event, e.g. if we want to test if the user pressed either of the following buttons, we can use:libGUI.match(event, EVT_VIRTUAL_ENTER, EVT_VIRTUAL_EXIT, EVT_VIRTUAL_MENU)

libGUI.newGUI()

This is the main function that creates a new GUI object. If an application has different screens, then a GUI object is created for each screen.

GUI Object Properties

GUI.fullScreenRefresh

A function f() to draw the screen background in full screen mode. The GUI elements are drawn afterwards on top.

GUI Object Functions

GUI.run(event, touchState)

Redraws the screen and processes key and touch events. It can directly replace a widget's refresh function, or it can be called by refresh.

GUI.setEventHandler(event, f)

Sets a function f(event, touchState) to handle an event. If no GUI element is being edited, then this can trap events before they are passed to the GUI, e.g. to press EXIT to go back to the previous screen. If f is nil, then the event handler is removed.

If the function returns another event value, then it is passed to the active screen element (i.e. the handler can modify certain events).

It cannot trap the events EVT_VIRTUAL_PREV, EVT_VIRTUAL_NEXT as these events are used for navigation. If elements are being edited, then this also takes precedence over the event handler.

GUI.showPrompt(guiPrompt)

This function can be used to show a modal prompt window, or trap events (alternative to setEventHandler). guiPrompt is a GUI or another Lua table with a function run(event, touchState).

When it is set, the main GUI will first be drawn, and then it will call guiPrompt.run(event, touchState) instead of its own onEvent function.

GUI.dismissPrompt()

Dismisses the prompt.

GUI Screen Elements

The screen elements are drawn in the order that they are added to the GUI, and touch events are sent to the first element that covers the touched point of the screen. GUI elements therefore should never overlap.

There are some common properties that can be set for all or most of the GUI elements.

element.disabled = true prevents the element from taking focus and receiving events, and disabled buttons are greyed out.
element.hidden = true in addition to the above, the element is not drawn.
element.title can be changed for elements with a title.
element.value can be changed for elements with a value.
element.flags drawing flags for the element's text. If no flags were given at element creation, it defaults to GUI.flags.

The various screen elements are added to the GUI with the functions described below. The functions all add the element to the GUI and returns a reference so the element subsequently can be accessed by the client.

GUI.button (x, y, w, h, title, callBack [, flags])

Add a button to the GUI.

When tapped, it calls callBack(self) so a call back function can tell which button activated it.

GUI.toggleButton(x, y, w, h, title, value, callBack [, flags])

Add a toggle button to the GUI.

The value is either true or false.

When tapped, it calls callBack(self) so a call back function can tell which toggle button activated it, and what self.value is.

GUI.number(x, y, w, h, value, changeValue [, flags])

Add an editable number to the GUI.

The value can be either a number or text. By setting the value to a text, it can be shown that the number is not present e.g. by "- -" or similar.

When tapped, the number will go to edit mode. In edit mode, and changeValue(d, self) is called if the increase/decrease buttons are pressed, or a finger is slided up or down from the number. The parameter d is the number of "ticks" by which the number is being changed, and changeValue must return the new value for the number. In a simple case, the new value would just be self.value + d, but it could also select new values from a table etc.

GUI.timer(x, y, w, h, tmr, changeValue [, flags])

Add a timer to the GUI.

If no value is present, then the model timer tmr will be shown. If value is a number, then it indicates the time in seconds, and it will be shown as MM:SS. The value can also be text, e.g. "- - : - -" to show that the timer is disabled.

When tapped, the timer will go to edit mode, as described above for number.

GUI.label(x, y, w, h, title[, flags])

Add a text label to the GUI.

The label does not respond to any events, but its title and flags can be changed.

Add a scrollable menu to the GUI.

items is a table with the menu item texts.

When a menu item is tapped, it calls callBack(self) and self.selected gets the index of the selected item.

Add a field with values that can be selected on a drop down menu.

items is a table with the items that can be selected from.

selected is the index of the initially selected item.

When an item has been selected, it calls callBack(self). The index of the selected item is given by self.selected.

GUI.gui.horizontalSlider(x, y, w, value, min, max, delta, callBack)

Adds a horizontal slider that starts at (x, y) and has the width w.

value is the initial value, and min - max is the interval of values that can be selected with step size delta.

When the value is changed, callBack(self) is called, and the value is given by self.value.

GUI.gui.verticalSlider(x, y, w, value, min, max, delta, callBack)

The same as the above, just vertical.

gui.custom(self, x, y, w, h)

This can be used to create your own custom GUI elements. self is a table containing the element. You must define the functions self.draw(focused) and self.onEvent(event, touchState). There is a function self.drawFocus(color) defined that can draw a border around the element (use if focused == true).

gui.gui(x, y, w, h)

Create a nested sub-GUI. This can be used to group GUI elements which will be offset by (x, y) relative to the parent GUI.

Drawing Flags and Colors

This section will give some technical details for radios with a color screen.

An argument with drawing flags can be given to the various functions that draw on the LCD screen. The lower half of the flags (bits 1-16) are the flag attributes shown below, and the upper half of the flags (bits 17-32) are a color value.

Not all of the flags below should be directly manipulated from Lua, but those that are meant to be set directly by Lua, are accessible by the Lua flag constants.

Since the flags are bits, you can add them up to combine, as long as you only add each flag one time. If you add the same flag twice, then it will add up to the next bit over, e.g. INVERS + INVERS = VCENTER. If you want to add a flag to a value where it may already be set, then use flags = bit32.bor(flags, INVERS).

RGB_FLAG decides how the color value is encoded into the upper half (bits 17-32).

If RGB_FLAG = 0, then an index into a color table is stored. This color table holds a default color (index 0), the theme colors, and CUSTOM_COLOR. The entries in the color table can be changed with the function lcd.setColor. The advantage of this system is that the color changes everywhere that this indexed color is used, and this is how different color themes are created. Notice that changing the theme colors affects the entire user interface of your radio!!

If RGB_FLAG = 1, then a 16-bit RGB565 color is stored. This is used directly by the system to draw a color on the screen.

You should not change RGB_FLAG explicitly; this is handled automatically by the various functions and Lua constants. But you should be aware of the following.

lcd.setColor must have an indexed color as its first argument, because this will be the index of the color in the table being changed. Giving another color, e.g. ORANGE, as the first argument will result in nothing.
If no color is given to the flags with a drawing function, RGB_FLAGS = 0 and the color index = 0. Therefore, the default color is stored in the color table under this index, and you can change the default color with lcd.setColor(0, color).
lcd.getColor always returns a RGB color. This can be used to "save" an indexed color before you change it.
lcd.RGB obviously returns a RGB color.

Colors in EdgeTX versus OpenTX

OpenTX only supports indexed colors in drawing functions, so you must first call lcd.setColor to change e.g. CUSTOM_COLOR, and then call the LCD drawing function with that indexed color. In EdgeTX, you can use either type of color for drawing functions, so you are no longer forced to constantly call lcd.setColor. You can also store any color in local variables, and then use these when drawing, thus effectively creating your own color theme.

In OpenTX, lcd.RGB returns a 16 bit RGB565 value, but in EdgeTX it returns a 32 bit flags value with the 16 bit RGB565 value in the upper half (bits 17-32). Therefore, colors in EdgeTX are not binary compatible with colors in OpenTX. But if you use the functions lcd.RGB, lcd.setColor, and lcd.getColor, then your code should work the same way in EdgeTX as in OpenTX.

Unfortunately, OpenTX has disabled the function lcd.RGB when the screen is not available for drawing, so it can only be called successfully from the refresh function in widgets and from the run function in One-Time scripts. Therefore, some existing widget scripts set up colors with hard coded constants instead of calling lcd.RGB during initialization, and this is not going to work with EdgeTX, because of the different binary format.

A pull request has been submitted to OpenTX, allowing lcd.RGB to work also during widget script initialization, and hopefully, it will be merged into OpenTX 2.3.15. If that happens, then the obvious way to solve the problem is to use lcd.RGB values instead of hard coded color constants. But in the meantime, the following RGB function can be used for setting up colors in a way that works for both EdgeTX and OpenTX.

local function RGB(r, g, b)
  local rgb = lcd.RGB(r, g, b)
  
  if not rgb then
    rgb = bit32.lshift(bit32.rshift(bit32.band(r, 0xFF), 3), 11)
    rgb = rgb + bit32.lshift(bit32.rshift(bit32.band(g, 0xFF), 2), 5)
    rgb = rgb + bit32.rshift(bit32.band(b, 0xFF), 3)
  end
  
  return rgb
end

This functions calls lcd.RGB, and if it gets a nil value (because we are running a widget script under OpenTX, and it is not called from the refresh function) then it creates the 16-bit RGB565 value that OpenTX wants.

Data Exchange with the EdgeTX Model Setup

An EdgeTX model has several data components that can be exchanged with Lua scripts. This section gives an overview.

In general terms, there are two different types of data that can be exchanged with EdgeTX:

Values, which generally fall on a scale between -1024 and 1024, also sometimes reported as -100% to 100%, e.g. for mixer values and channel outputs.
Switches, which are either true or false.

A specific data source type, e.g. Global Variables, can be indexed directly with an index that starts with 0 for the first one. This can be a little confusing, as e.g. GV1 for FM0 is read with model.getGlobalVariable(0, 0), because GV1 is the first global variable, and FM0 is the first flight mode. But as long as you remember that all direct indices start with 0 for the first one, you should be fine!

Global Variables is a value data source that can return a value between -1024 and 1024. Examples of value sources are:

Global Variables
Sticks, sliders and knobs
Trim values
Input lines
Channel outputs
Trainer channel inputs
Telemetry sensors

There is a way to access a value of any such type with a meta-index. You use the function getFieldInfo(name) where name can be any of the valid source names listed here. It returns a table with a description of the value source, including the field id, which is the meta-index.

You can use id with the function getValue(id) to read the current value. You can also use name directly, but this is less efficient, as EdgeTX does a linear search for the name every time it is called. Therefore, the procedure of first extracting the meta-index from getFieldInfo(name).id, and then using that, is recommended.

For switches, getLogicalSwitchValue(index) uses a direct index to read this specific type of switch sources, again using the index 0 for LS1 etc. But there are also several types of switch sources, such as:

Logical switches
Switch positions, testing if a physical switch is in a particular position, e.g. SA↑.
Trim buttons
Transmitter and telemetry activity

You can find the meta-index of a particular switch source with getSwitchIndex(name), where name is exactly the name that you see in the radio menus where you can select a switch source.

You can read the current value of a switch source with getSwitchValue(index) as a true/false value.

It can be very confusing that some source can be read both as a value and as a switch. As an example, elevator trim can be read as the current value of the trim:

local id = getFieldInfo("trim-ele")
local eleTrim = getValue(id)

Or it can be read as the current value of the trim button position:

local idUp = getSwitchIndex(CHAR_TRIM .. "Eu")
local idDown = getSwitchIndex(CHAR_TRIM .. "Ed")
local eleUp = getSwitchValue(idUp)
local eleDown = getSwitchValue(idDown)

These are really two different things, as the elevator trim is an internal value stored by the radio, which is changed with the trim button, and the button is a physical button.

But it can also be a more direct comparison, e.g. the 3-position switch B, which can be read as a value source with:

local idB = getFieldInfo("sb")
local swBvalue = getValue(idB) -- a value of -1024, 0 or 1024

Or the current position of switch B can be read with:

local idBup = getSwitchIndex("SB" .. CHAR_UP)
local idBdown = getSwitchIndex("SB" .. CHAR_DOWN)
local swBup = getSwitchValue(idBup)
local swBdown = getSwitchValue(idBdown)

Hopefully, these examples illustrated the differences between values and switches, and showed how these can be retrieved in a Lua script.

You can also send data the other way: from Lua to the EdgeTX model setup.

To send a value, use a global variable: model.setGlobalVariable(index, fm, value). If you use the default GV setting, where all other flight modes use the value of FM0, then you can use 0 for fm.

To send a switch, setup a STICKY type logical switch, and then use setStickySwitch(index, true/false).

The following table gives an overview of the Lua API functions that can be used to exchange data with the EdgeTX model setup.

Included Lua Libraries

Lua Standard Libraries

Included

io Library

The io library has been simplified and only a subset of functions and their functionality is available. What follows is a complete reference of io functions that are available to EdgeTX scripts

Available functions:

io.open()
io.close()
io.read()
io.write()
io.seek()

Examples

Read the whole file

-- this is a stand-alone script

local function run(event)
  print("lua io.read test")         -- print() statements are visible in Debug output window
  local f = io.open("foo.bar", "r")
  while true do
    local data = io.read(f, 10)     -- read up to 10 characters (newline char also counts!)
    if #data == 0 then break end    -- we get zero length string back when we reach end of the file
    print("data: "..data)
    end
  io.close(f)
  return 1
end

return {  run=run }

Append data to file

-- this is a stand-alone script

local function run(event)
  print("lua io.write test")
  local f = io.open("foo.bar", "a")        -- open file in append mode
  io.write(f, "first line\r\nsecond line\r\n")
  io.write(f, 4, "\r\n", 35.6778, "\r\n")  -- one can write multiple items at the same time
  local foo = -4.45
  io.write(f, foo, "\r\n")
  io.close(f)
  return 1    -- this will end the script execution
end

return { run=run }

io.close()

The io.close() function is used to close open file.

Parameters

file object a file object that was returned by the io.open() function.

Return value

none

io.read()

The io.read() function is used to read data from the file on SD card.

Notice: other read commands (like "all", etc..) are *not supported.

Parameters

file object a file object that was returned by the io.open() function. The file must be opened in read mode.
length number of characters/bytes to read. The number of actual read/returned characters can be less if the file end is reached.

Return value

<string> a string with a length equal or less than
"" a zero length string if the end of file was reached

io.write()

The io.write() function is used to write data to the file on SD card.

Parameters

file object a file object that was returned by the io.open() function. The file must be opened in write or append mode.
data any Lua type that can be converted into string. If more than one data parameter is used their contents are written to the file by one in the same order as they are specified.

Return value

<file object> if data was successfully opened.
nil, <error string>, <error number> if the data can't be written.

io.seek()

The io.seek() function is used to move the current read/write position.

Notice: other read standard seek bases (like "cur", "end") are not supported.

Parameters

file object a file object that was returned by the io.open() function.
offset position the read/write file pointer at the specified offset from the beginning of the file. If specified offset is bigger than the file size, then the pointer is moved to the end of the file.

Return value

0 success
<number> any other value means failure.

Part III - EdgeTX Lua API Reference

This section describes the Lua libraries, functions and constants that are provided by EdgeTX.

Constants

This section describes various constants that are provided for Lua by EdgeTX.

Key Event Constants

This page describes the value that is passed to scripts in the event parameter. It is used in Telemetry and One-Time scripts, as well as widget scripts in full screen mode.

The key event mechanism

Each time a key is pressed, held and released a number of events get generated. Here is a typical flow:

when a key is pressed a FIRST event is generated
if the key continues to be pressed, then after a while a LONG event is generated
if the key continues to be pressed, then a REPEAT events are being generated
when the key is released a BREAK event is generated

Couple of examples:

a short press on key would generate: FIRST, BREAK
a longer pres on key would generate: FIRST, LONG, BREAK
even longer press: FIRST, LONG, REPEAT,REPEAT, ..., BREAK

This normal key event sequence can be altered with the killEvents(key) function. Any time this function is called (after the FIRST event) all further key events for this key will be suppressed until the next key press of this key. Examples:

kill immediately after the key press would generate: FIRST
kill after the long key press would generate: FIRST, LONG

Constants

The event parameter in the Telemetry and One-Time scripts run function actually carries two pieces of information:

key number
type of event

The two fields are combined into one single number. Some of these combinations are defined as constants and are available to Lua scripts:

Radios with rotary encoder (X7 and Horus) have also:

Virtual events

Given the large number of radios supported by OpenTX, and the large difference in keys available on those, a set of VIRTUAL KEYS has been defined and are mapped to best fit available hardware

Touch Event Constants

In addition to the key events described in the previous section, radios with a color touch screen also provide touch events to the widget scripts.

The following touch events are passed in the event argument to the widget script refresh function (when in full screen mode), just like the key events. The following touch events are provided:

Touch Event Name

Description

In addition to the above touch events a touchState table is passed to refresh with the following addional data fields:

touchState fields

Description

Notes:

touchState is nil if event is not a touch event. This can be used to test if we have a touch event or a key event.
- Since Lua evaluates a nil value to false and everything else to true:
- if touchState then we have a touch event.
x, y are present for all touch events.
startX, startY, slideX, slideY are only present with EVT_TOUCH_SLIDE.
swipeUp / swipeDown / swipeLeft / swipeRight may be present only withEVT_TOUCH_SLIDE.
tapCount is zero for anything but EVT_TOUCH_TAP.

Flags and Pattern Constants

Many of the lcd functions accept parameters named flags and patterns. The names and their meanings are described below.

Flags

Name

Description

Version

Notes

Patterns

Color Constants

On radios with color display, a color may be added to the flags described above.

There are two types of color constants: one that is an index into a table holding a palette of theme colors, and one that is just a color.

Indexed colors

These are the theme colors plus CUSTOM_COLOR, and they can be changed with the function lcd.setColor(color_index, color). Please note: if an indexed color is changed, then it changes everywhere that it is used. For the theme colors, this is not only in other widgets, but everywhere throughout the radio's user interface!

COLOR_THEME_PRIMARY1
COLOR_THEME_PRIMARY2
COLOR_THEME_PRIMARY3
COLOR_THEME_SECONDARY1
COLOR_THEME_SECONDARY2
COLOR_THEME_SECONDARY3
COLOR_THEME_FOCUS
COLOR_THEME_EDIT
COLOR_THEME_ACTIVE
COLOR_THEME_WARNING
COLOR_THEME_DISABLED
CUSTOM_COLOR

Literal colors

These color constants cannot be changed:

BLACK
WHITE
LIGHTWHITE
YELLOW
BLUE
DARKBLUE
GREY
DARKGREY
LIGHTGREY
RED
DARKRED
GREEN
DARKGREEN
LIGHTBROWN
DARKBROWN
BRIGHTGREEN
ORANGE

Deprecated color constants

These should no longer be used, but they are included for backwards compatibility. The old OpenTX API had a large number of indexed theme colors, and these have been mapped to the new theme colors as follows:

ALARM_COLOR -> COLOR_THEME_WARNING
BARGRAPH_BGCOLOR -> COLOR_THEME_SECONDARY3
BARGRAPH1_COLOR -> COLOR_THEME_SECONDARY1
BARGRAPH2_COLOR -> COLOR_THEME_SECONDARY2
CURVE_AXIS_COLOR -> COLOR_THEME_SECONDARY2
CURVE_COLOR -> COLOR_THEME_SECONDARY1
CURVE_CURSOR_COLOR -> COLOR_THEME_WARNING
HEADER_BGCOLOR -> COLOR_THEME_FOCUS
HEADER_COLOR -> COLOR_THEME_SECONDARY1
HEADER_CURRENT_BGCOLOR -> COLOR_THEME_FOCUS
HEADER_ICON_BGCOLOR -> COLOR_THEME_SECONDARY1
LINE_COLOR -> COLOR_THEME_PRIMARY3
MAINVIEW_GRAPHICS_COLOR -> COLOR_THEME_SECONDARY1
MAINVIEW_PANES_COLOR -> COLOR_THEME_PRIMARY2
MENU_TITLE_BGCOLOR -> COLOR_THEME_SECONDARY1
MENU_TITLE_COLOR -> COLOR_THEME_PRIMARY2
MENU_TITLE_DISABLE_COLOR -> COLOR_THEME_PRIMARY3
OVERLAY_COLOR -> COLOR_THEME_PRIMARY1
SCROLLBOX_COLOR -> COLOR_THEME_SECONDARY3
TEXT_BGCOLOR -> COLOR_THEME_SECONDARY3
TEXT_COLOR -> COLOR_THEME_SECONDARY1
TEXT_DISABLE_COLOR -> COLOR_THEME_DISABLED
TEXT_INVERTED_BGCOLOR -> COLOR_THEME_FOCUS
TEXT_INVERTED_COLOR -> COLOR_THEME_PRIMARY2
TITLE_BGCOLOR -> COLOR_THEME_SECONDARY1
TRIM_BGCOLOR -> COLOR_THEME_FOCUS
TRIM_SHADOW_COLOR -> COLOR_THEME_PRIMARY1
WARNING_COLOR -> COLOR_THEME_WARNING

Special Character Constants

The radio's special characters can be used with the following text constants.

CHAR_RIGHT
CHAR_LEFT
CHAR_UP
CHAR_DOWN
CHAR_DELTA
CHAR_STICK
CHAR_POT
CHAR_SLIDER
CHAR_SWITCH
CHAR_TRIM
CHAR_INPUT
CHAR_FUNCTION
CHAR_CYC
CHAR_TRAINER
CHAR_CHANNEL
CHAR_TELEMETRY
CHAR_LUA

Screen Constants

Name

Description

Logical Switch Function Constants

These constants give the type of logical switch function.

LS_FUNC_NONE
LS_FUNC_VEQUAL
LS_FUNC_VALMOSTEQUAL
LS_FUNC_VPOS
LS_FUNC_VNEG
LS_FUNC_RANGE
LS_FUNC_APOS
LS_FUNC_ANEG
LS_FUNC_AND
LS_FUNC_OR
LS_FUNC_XOR
LS_FUNC_EDGE
LS_FUNC_EQUAL
LS_FUNC_GREATER
LS_FUNC_LESS
LS_FUNC_DIFFEGREATER
LS_FUNC_ADIFFEGREATER
LS_FUNC_TIMER
LS_FUNC_STICKY

Special Function Constants

These constants determine the type of a Special Function

FUNC_OVERRIDE_CHANNEL
FUNC_TRAINER
FUNC_INSTANT_TRIM
FUNC_RESET
FUNC_SET_TIMER
FUNC_ADJUST_GVAR
FUNC_VOLUME
FUNC_SET_FAILSAFE
FUNC_RANGECHECK
FUNC_BIND
FUNC_PLAY_SOUND
FUNC_PLAY_TRACK
FUNC_PLAY_VALUE
FUNC_PLAY_SCRIPT
FUNC_RESERVE5
FUNC_BACKGND_MUSIC
FUNC_BACKGND_MUSIC_PAUSE
FUNC_VARIO
FUNC_HAPTIC
FUNC_LOGS
FUNC_BACKLIGHT
FUNC_SCREENSHOT
FUNC_RACING_MODE
FUNC_DISABLE_TOUCH

General Functions

GREY()

Returns gray value which can be used in LCD functions

@status current Introduced in 2.0.13

Parameters

none

Return value

(number) a value that represents amount of greyness (from 0 to 15)

Notice

Only available on Taranis

accessTelemetryPush()

This functions allows for sending SPORT / ACCESS telemetry data toward the receiver, and more generally, to anything connected SPORT bus on the receiver or transmitter.

When called without parameters, it will only return the status of the output buffer without sending anything.

@status current Introduced in 2.3

Parameters

module module index (0 = internal, 1 = external)
rxUid receiver index
sensorId physical sensor ID
frameId frame ID
dataId data ID
value value

Return value

boolean data queued in output buffer or not.

chdir(directory)

Change the working directory

@status current Introduced in 2.3.0

Parameters

directory (string) New working directory

Return value

none

crossfireTelemetryPop()

Pops a received Crossfire Telemetry packet from the queue.

@status current Introduced in 2.2.0

Parameters

none

Return value

nil queue does not contain any (or enough) bytes to form a whole packet
multiple returns 2 values:
- command (number)
- packet (table) data bytes

Model Functions

loadScript(file [, mode], [,env])

Load a Lua script file. This is similar to Lua's own loadfile() API method, but it uses OpenTx's optional pre-compilation feature to save memory and time during load.

Return values are same as from Lua API loadfile() method: If the script was loaded w/out errors then the loaded script (or "chunk") is returned as a function. Otherwise, returns nil plus the error message.

@status current Introduced in 2.2.0

Example

  fun, err = loadScript("/SCRIPTS/FUNCTIONS/print.lua")
  if (fun ~= nil) then
     fun("Hello from loadScript()")
  else
     print(err)
  end

Parameters

file (string) Full path and file name of script. The file extension is optional and ignored (see mode param to control which extension will be used). However, if an extension is specified, it should be ".lua" (or ".luac"), otherwise it is treated as part of the file name and the .lua/.luac will be appended to that.
mode (string) (optional) Controls whether to force loading the text (.lua) or pre-compiled binary (.luac) version of the script. By default OTx will load the newest version and compile a new binary if necessary (overwriting any existing .luac version of the same script, and stripping some debug info like line numbers). You can use mode to control the loading behavior more specifically. Possible values are:
- b only binary.
- t only text.
- T (default on simulator) prefer text but load binary if that is the only version available.
- bt (default on radio) either binary or text, whichever is newer (binary preferred when timestamps are equal).
- Add x to avoid automatic compilation of source file to .luac version.
  Eg: "tx", "bx", or "btx".
- Add c to force compilation of source file to .luac version (even if existing version is newer than source file).
  Eg: "tc" or "btc" (forces "t", overrides "x").
- Add d to keep extra debug info in the compiled binary.
  Eg: "td", "btd", or "tcd" (no effect with just "b" or with "x").
env (integer) See documentation for Lua function loadfile().

Return value

function The loaded script, or nil if there was an error (e.g. file not found or syntax error).
string Error message(s), if any. Blank if no error occurred.

Notice

Note that you will get an error if you specify mode as "b" or "t" and that specific version of the file does not exist (eg. no .luac file when "b" is used). Also note that mode is NOT passed on to Lua's loader function, so unlike with loadfile() the actual file content is not checked (as if no mode or "bt" were passed to loadfile()).

2.7

EdgeTX 2.7 Lua Reference Guide

Introduction

Acknowledgments

Getting Started

Downloading EdgeTX Companion

Enabling support for Mixer Scripts

Part I - Script Type Overview

Custom (Mixer) Scripts

Overview

Typical uses

Limitations

Lifetime

Disabled script

File Location

Interface

Example

Input table

Output table

One-Time Scripts

Overview

Lifetime

File Location

Interface

Example

Notes:

Function Scripts

Overview

Lifetime

File Location

Interface

Example

Widget Scripts

Overview

Lifetime

File Location

Interface

Example

Notes

Part II - EdgeTX Lua API Programming Guide

Lua Basics

Introduction

First Class Functions

Closures

Functions with Variable Number of Arguments

References

Loading Code Modules Dynamically

Saving Memory

Telemetry Script Radios

Widget Script Radios

Using Key and Touch Events

EventDemo Widget

LibGUI

libGUI Properties

libGUI.flags

libGUI.colors

libGUI.widgetRefresh

libGUI Functions

libGUI.match(x, ...)

libGUI.newGUI()

GUI Object Properties

GUI.fullScreenRefresh

GUI Object Functions

GUI.run(event, touchState)

GUI.setEventHandler(event, f)

GUI.showPrompt(guiPrompt)

GUI.dismissPrompt()

GUI Screen Elements

GUI.button (x, y, w, h, title, callBack [, flags])

GUI.toggleButton(x, y, w, h, title, value, callBack [, flags])

GUI.number(x, y, w, h, value, changeValue [, flags])

GUI.timer(x, y, w, h, tmr, changeValue [, flags])

GUI.label(x, y, w, h, title[, flags])

GUI.menu(x, y, w, h, items, callBack [, flags])

GUI.dropDown(x, y, w, h, items, selected, callBack, flags)

GUI.gui.horizontalSlider(x, y, w, value, min, max, delta, callBack)

GUI.gui.verticalSlider(x, y, w, value, min, max, delta, callBack)

gui.custom(self, x, y, w, h)

gui.gui(x, y, w, h)

Drawing Flags and Colors