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The further installation is explained in detail at httphttps://wwwlejos.lejossourceforge.orgio/nxt/nxj/tutorial/Preliminaries/GettingStarted.htm.
Do not forget to flash the download leJOS firmware to the Mindstorms brick as explained in the tutorial!
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Furthermore, to use USB connection, a java library has to be compiled via ant. To do this perform cd /path/to/leJOS/build and start ant. If the ant build tool is not installed on your system, you can do so via sudo apt-get install ant.
On Linux there is on an issue that the NXT is found, but uploading any file to it does not progress after Found nxt <name>. Try to connect via bluetooth (-b option) if this is the case.
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The setup.exe of the current LEGO Fantom driver for Windows (1.2.0) has an awkward issue. If you get an error message (Developer Error) because an .msi file could not be found, don't panic. The file is part of the downladed downoladed archive (in the Products folder) but you have to start it manually. You may also try to install the necessary drivers by following the Guide to install on Windows 10 on Reddit.
If you get a runtime error when starting the ssetusetup.exe also don't panic. The file is part of the downladed downloaded archive (in the Products folder) but you have to start it manually.
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A simple Hello World application for the Mindstorms is developed as part of the leJOS tutorial.
If get a compilation error, set the java compliance level (target and source are necessary if you are using java 11 or something like that and have not set LEJOS_NXT_JAVA_HOME to a java 8 installation).
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There are several wrapper code snippets that can be used as annotations on input and output variables in the model file. These snippets are inserted in the main file template as part of the project build. The available snippets are listed below here.
For sensors, the port has to be on of S1, S2, S3, S4.
For motors / actuators the port has to be one of A, B, C.
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Resets a clock, such that the full time interval of the clock has to elapse, before the clock will be set to true again.
If autoFalse is true, the reset variable will be set to false automatically.
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Delays the execution until the tick loop takes at least as long as the given target duration.
The input variable is set to the actual tick loop duration.
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Should be used on the very first input variable in the model, such that waiting is the last action in the tick loop.
In case the actual tick loop duration is longer than the target duration, the modeler can provide some error handling.
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Sets the input variable to the current system time (milliseconds). The model can add to this variable to get a new value. This is the next system time the tick function will be called.
In other words, the next tick function call is delayed until the wake up time has been reached.
For instance the statement nextTickWakeUp += 500 could be used to call the tick function again in 500 milliseconds, if nextTickWakeUp is an input with the corresponding annotation.
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Should be used on the very last input variable in the model, such that waiting and settings the system time is the last action done, before the tick function call.
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Reads the value of a light sensor.
If percentValue is true, the a percent value is returned, based on the light sensor calibration.
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output
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output
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Lets a motor rotate the variable value in degrees. This is only done if the value is unequal zero. If the value is negative, the motor rotates backwards. The variable is set to zero afterwards, such that setting the variable once to a value X, will let the motor rotate X degrees.
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Plays a sequence of tones in either ascending or descending tone frequency if the variable is true.
The variable is set to false automatically.
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direction has to be one of Up, Down
default volume is 10
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ouput bool @macro "PlayTone", "440", "100", "10" A4
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Not available on NXT
mode hat to be one of Angle, Rate
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Resets a gyroscope if the variable is true.
If autoReset is true, the variable is set to false automatically.
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Using the Remote Console (RConsole)
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Using the Remote Console (RConsole)
The display of the NXT brick is rather small compared to a Monitor. To ease debugging, one can print to a Remote Console (RConsole). This enables easier collection for example of sensor data.
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The following presents typical issues and how to solve them.
| Issue | Typical Error Messages | Description | Solution |
|---|---|---|---|
| leJOS EV3 does not support Java 8 | "java.lang.UnsupportedClassVersionError" "unsupported major.minor version" | You compile the sources in your project with Java 8 and upload them to the brick. However the lejos EV3 does not support Java 8 | Go to the project properties and switch to Java 7 (Right Click on project > Properties > Java Compiler > Compiler compliance level) |
Uploading to the brick does not respond | You compile a file successfully and when uploading the result, the connected brick is found. Anyway the upload does not terminate and does not react. | Flash the brick with the current leJOS firmware. If the brick is recognized correctly and the attempt to upload a compiled file fails then the firmware on the brick might be outdated. If connecting via bluetooth works add -b to the uxjupload/nxj command. | |
| Compilation and uploading works from command line but not when using KIELER | This Java instance does not support a 32-bit JVM. Please install the desired version. | You can compile and upload code to the brick using the command line tools but when using KIELER an error message apprears because Java does not support 32-bit JVM. | Set the LEJOS_NXT_JAVA_HOME environment variable, such that it points to an 32-bit JDK and is visible for GUI applications (or at least KIELER). The process to do so differs on every OS. As alternative, execute KIELER from terminal. |
| Brick does nothing after program finished and prints "Program exit" | A program was uploaded and finished without errors. Afterwards the brick prints "Program exit" but does not open the main menu. | This is normal behaviour if uploading a program in debug mode instead run mode (Debug As instead Run As in Eclipse). To get back to the main menu, press the ENTER and ESCAPE button of the brick at the same time. | |
| Cannot simulate but compile | Javac/gcc not found | Javac and gcc have to be available in the path | Add javac/gcc to your path |
| Cannot simulate but compile | Cannot find file | KIELER has no rights to write to the file system | Use a workspace in which KIELER has write access |
| LEFT and RIGHT button cannot be pressed at the same time | If you press the ENTER and LEFT button both are true, if you press the ENTER and RIGHT button both are true. If you press the LEFT and RIGHT button only the LEFT button is true. | Do not write a program that requires the LEFT and RIGHT button to be presssed at the same time. | |
| Too many variables | No more than 255 fields expected | If your generated Java Code uses more than 255 variables it cannot run on the NXT. | Try using less super states or concurrent regions (during actions create concurrent regions). |
| KIELER and compilation use two different java versions | Main |
has |
been |
compiled |
by |
a |
more |
recent |
version |
of |
the |
Java |
Runtime |
(class |
file |
version |
55.0), |
version |
of |
the |
Java |
Runtime |
only |
recognizes |
class |
file |
versions |
up |
to |
52.0 | Make sure KIELER uses the same java version as the one in the path (for example Java 11). Lejos can still use java 8, if you set the LEJOS_NXT_JAVA_HOME variable (in windows this is a 32-bit java installation) | ||
| NXT program cannot be stopped in RConsole mode | You deploy a program to the NXT with RConsole enabled | Press Esc (dark grey button) and Enter (organge Button) at the same time |
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