Lua extensions

A Lua extension adds user-defined features to the SimTX Transmitter. An extension may provide modulation modes, audio add-ons, tools, themes, reusable libraries, or several of these features in one package. Extensions are stored as folders and can be created, edited, and reloaded without restarting the application.

Extension types

Type	Purpose	Where it appears
Modulation	Produces complex IQ or mono audio for a transmission. A mode may use ordinary audio, generate a signal, or consume an image, video, or data file.	Modulation list in the RF Signal section
Audio add-on	Processes mono audio before RF modulation. Examples include gain control, filtering, CTCSS, and identification tones.	Add-ons button in the footer
Tool or action	Reads or changes documented transmitter settings and may start or stop transmissions.	Extensions > Tools
Theme	Changes the application colors and fonts.	Theme list in the footer
Library	Provides Lua modules to other installed extension packages.	Used by declared dependent packages

One package may register several items and may combine several types.

Managing installed extensions

The Extensions button opens three tabs:

• Installed lists each package, its version, and the items it provides.
• Tools lists user-invoked actions and provides a button for running the selected action.
• Problems lists packages that could not be loaded and gives the reason.

The same window provides Create extension, Edit package, Open user folder, and Reload now. Changes made in the built-in editor or in the extension folder take effect after reloading. The application also detects ordinary file changes and reloads extensions automatically.

The first creation of the extension folder includes editable example packages. These demonstrate modulation, generated CW, image input, audio add-ons, actions, themes, multi-type packages, libraries, and dependencies.

Using extension features

Extension modulation modes are selected in the normal Modulation list. Their controls and required media pickers appear below the standard transmission fields. Audio-output modes also provide an RF modulation selector. IQ-output modes bypass the built-in modulator.

Audio add-ons are enabled and ordered through the Add-ons window. Enabled add-ons run from top to bottom. Their order, enabled state, and control values are retained between application runs. Add-ons require a mono audio source or an audio-producing Lua modulation.

Themes are selected from the Theme list. Tools are run from the Tools tab of the Extensions window.

Obtaining extensions

The Extension catalog is the normal way to preview and install shared packages. Catalog extensions are checked before installation, placed in the user extension folder, and loaded immediately. Required library packages can be installed as part of the same operation.

Creating extensions

Creating Lua extensions describes the package structure and a minimal example. The public interface is divided among these references:

• Lua extension manifest
• Lua extension API
• Lua modulation API
• Lua audio add-on API
• Lua action API
• Lua theme API

Execution environment

Extensions run in a restricted Lua environment intended for computation. Standard Lua base, table, string, coroutine, bit32, and mathematical facilities are available. Direct file access, operating-system commands, network access, Java access, the debug library, dofile, and loadfile are not available. Files selected through declared inputs are exposed as read-only objects described in Lua modulation API.

Extension callbacks have execution limits. Signal processing should use the block operations supplied by the API where possible. An extension that exceeds a limit, returns an invalid value, or raises an error is stopped with a diagnostic.