Writing Data in Lua


This example is generating data and writing it over DDS using Lua. This requires the RTI Prototyper with Lua, which is experimental in version 5.0.0, and can be downloaded from: http://community.rti.com/downloads/experimental/rti-prototyper-with-lua.

This is interesting for two reasons:

  1. This shows how to create simple DDS applications for prototyping or testing systems without generating data types from IDL or compiling code.
  2. This script can be modified as the Prototyper application is running, and the modifications will be applied immediately as soon as the script file is saved.

Example Description

In this example, the RTI Prototyper with Lua loads the XML configuration and a Lua script.

The XML file defines:

  1. A SensorData QoS profile.
  2. A TemperatureType data type.
  3. A domain 0 that uses the TemperatureType for a Temperature Topic.
  4. A configuration with a DataWriter that writes Temperature data.
  5. A configuration with a DataReader that reads Temperature data.

The Lua script accesses the DataWriter and data type that are defined in the XML file. It then generates data values between 0 and 120, and uses the DataWriter to write them.

The script stores the previous, max, and min temperatures in a global variable called TEMPERATURE. This is initialized only once when the script is loaded.

It accesses the DataWriter by name, using the following code:


Then, it increments or decrements the temperature, and updates the DataWriter's data instance with the latest values to write:

TemperatureWriter.instance['value'] = current
TemperatureWriter.instance['appID'] = APPID

Then, it writes the value to the network:


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This is a great example to get started! If you have any doubts about the Lua syntax, check this Lua 101 cheat sheet out