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README.md

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Software for the lego line written in LeJOS NXJ

This is an attempt at replacing the current matlab code, which has faults including:

  • Poor error handling
  • A lack of structured data, leading to lots of string parsing
  • requiring multiple open instances of matlab
  • inability to be run locally on the bricks

With code written in java.

Code structure

There are three folders in the root of the repo - remote, local, and shared

  • remote - code to be run on a PC to remote-control the entire line at once over the LCP protocol. Can make use of GUIs and advanced threading APIs.
  • local - code to be run on the NXT bricks, without a PC connection
  • shared - code that is used by both situations. Note that the source is being shared, not the binary. This is important, as sometimes a class of the same name does not have the same members in the LeJOS API as it does on the PC side. When writing this code, try to use the lejos.robotics interfaces as much as possible, as interfaces are the same on both sides

The first two contain eclipse projects, which automatically load up the shared folder

Getting set up

  • Install the Eclipse IDE for java developers
  • Install the Java SE Development Kit 7 (LeJOS does not work with the newer 8)
  • Install the patched version of lejos (see below).
  • Install the LeJOS NXJ plugin into eclipse
    • Then open Window → Preferences → LeJOS, and change the LeJOS Home variable to point at the patched version
  • Import this project into eclipse, using Import projects → git → clone

Patched LeJOS

There is a patched LeJOS version at https://github.com/lego-line/lejos. This patch fixes bugs related to remote motor control, including:

  • Changing the speed of a running motor
  • Allowing a motor to be floated when stopped
  • Making remote control threadsafe
  • Allowing motors to be used in unregulated mode (ie for intentional stalling)

A build of the patch version is committed in the snapshot directory. Download this directory to your computer.

You'll then need to run snapshot/bin/flashg.bat to program the NXT with the snapshot firmware. Finally, the eclipse plugin should be pointed at this snapshot directory.

Rebuilding the snapshot

This shouldn't be necessary, normally

To rebuild the patched version, check out the git repository from above, and import the "snapshot" project into eclipse. Then right click on the build.xml file within the project, and hit "Run as → Ant build". This will rebuild the snapshot.

Running the sample

A sample program can be found in legoline.tools.ManualControl.java. This finds connected bricks with names starting "Merge" and "Feeder", and provides a GUI for controlling each one.