Lua on Jeti transmitters

Some time ago there was surfacing rumors that Jeti would implement Lua-scripting to transmitters. I immediately thought that this is something really cool and useful since Jeti transmitters are already a little bit of “geek’s wet dream” what comes to free programming and creativity to do things. (No, Jeti TX is NOT hard to use, you can make it hard to use if you want to, and I do…)

What is Lua?

Lua (“Loo-ah”, Portuguese for “Moon”) is a scripting language, short and simple. I think the description from Lua-projects homepage says it absolutely great: “Lua combines simple procedural syntax with powerful data description constructs based on associative arrays and extensible semantics. Lua is dynamically typed, runs by interpreting bytecode for a register-based virtual machine, and has automatic memory management with incremental garbage collection, making it ideal for configuration, scripting, and rapid prototyping.

What transmitters will be using Lua?

Lua is available on all DC/DS-14/16/24 transmitters. (14/16 from firmware 4.22). Difference between 14/16 and 24 is the amount of apps at the same time (2 vs 10) and a very hard memory limitation on 14/16. Running any Lua-apps on 14/16 that uses more than 50KB of memory causes Lua to be stopped entirely. So in practice code needs to be optimized and one big step is to run compiled versions (.lc) instead of .lua scripts.

How do you use it?

Basic setup is easy. You write an application (script) and put that to SD-card. After that the application is run in your selected model. This means you can have different scripts running on different models.

You can for example have constantly updating telemetry-data, make and use graphics and images, use telemetry and voice in a new fashion, you can access SD-card with Lua and so on. One thing I really like that like there is now MX1 – MX16 there will be Lua-controls. If nothing else this opens a whole new world to making transmitter and it’s functions really “your own”!

How does Lua-script look like?

It’s fairly simple. Since Jeti’s documentation to Lua is still on works we do of course not know what are the things we can control and so on. But this should give you a a hint:

For example a screen with fading text:

local slide1={
  listItem("» 24 proportional channels",0,10000),
  listItem("» Dual band 2.4GHz & 900MHz",1000,10000),
  listItem("» Haptic feedback",2000,10000),
  listItem("» Voice commands",3000,10000),
  listItem("» MP3 playback",4000,10000),
  listItem("» Model & background images",5000,10000),
  listItem("» FM Tuner",6000,10000),  
}

Here’s the functions for getting information about the state of input’s, information where to load image-files and so on.

local function init()
  system.registerForm(1,MENU_MAIN,appName,initForm,keyPressed,printForm);
  system.registerTelemetry(1,"Scriptable telemetry",3,printTelemetry);
  system.registerTelemetry(2,"Scriptable map",4,printTelemetryMap);
  p1,p2,p3,p4 = system.getInputs("P1", "P2", "P3", "P4")
  lastTimeMoved = system.getTimeCounter()
  for i=1,100 do
    values[i] = 0
  end 
  logolua = lcd.loadImage("Apps/img/logolua.png")
  imgmap = lcd.loadImage("Apps/img/map.jpg")
  imggear = lcd.loadImage("Apps/img/gear.jpg")
  imggraph = lcd.loadImage("Apps/img/graph.jpg")
end

Video

And since we all know a picture says more than a thousand words then a video should say more than two thousand words. This is a function-demo of Lua-scripted screens (some of code above). The quality is not the point in this case, contents is.

Script-examples and function-demo video from Jetimodel, published with permission.

Conclusion

If there’s ever been a doubt in my mind about getting the DS-24 that doubt is gone. I just GOT to have one…