Page History
...
Several open-source, third-party replacements for the offical Lego firmware have been developed. These support many well known programming languages, such as Java, C/C++, Python, Lua, etc. In the following we will use KIELER SCCharts to program Mindstorms running the Lego Java Operating System (leJOS). Therefore we will first install leJOS NXJ and flash its firmware. Afterwards we will create a simple SCCharts project in KIELER that we will compile and deploy to the NXT brick.
If you want to learn the SCCharts langugage first, you can follow these links:
...
Download and install leJOS
...
For motors / actuators the port has to be one of A, B, C, D.
| Snippet Name and Parameters | Description | Use on | Variable type | Remark | Defined in File |
|---|---|---|---|---|---|
| Clock, milliseconds | Sets a variable to true if the time in milliseconds passed | input | bool | See also ResetClock. | timing.ftl |
| ResetClock, clockVariableName, autoFalse | Resets a clock, such that the full time intervall 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. | output | bool | autoFalse is true per default. | timing.ftl |
| Time | Reads the elapsed time since program start | input | int | timing.ftl | |
| TickDuration, targetInMilliseconds | 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. | input | int | Should be used on the very first input variable in the model, such that waiting is the last action in the tick loop. | timing.ftl |
| Sleep | Lets the current thread sleep the time in milliseconds of the variable value. | output | int | timing.ftl | |
| Print, autoReset | Prints a string variable if the string is not empty. If autoReset is true then the string variable is set to the empty string after it has been printed | output | string | autoReset is true per default. | print.ftl |
| DrawString, x, y | Prints a string to the given x and y coordinate on the LCD. | output | string | print.ftl | |
| Button, buttonId | Sets a variable to true iff the button on the Mindstorms device is pressed. | input | bool | The buttonId has to be one of ENTER, LEFT, RIGHT | touch_and_buttons.ftl |
| TouchSensor, port | Sets a variable to true iff the touch sensor on the given port is pressed. | input | bool | touch_and_buttons.ftl | |
| LightSensor, port, percentValue | Reads the value of a light sensor. If percentValue is true, the a percent value is retured, based on the light sensor calibration. | input | int | percentValue is not available on EV3 | light.ftl |
| CalibrateLightSensor, port, signal | Calibrates a light sensors high or low values. This means if the variable is true, the current value of the light sensor is taken as its reference high / low value. | output | bool | signal has to be one of High, Low | light.ftl |
| Floodlight, port | Reads / Sets the state of the red lamp of the light sensor. | input output | bool | light.ftl | |
| RCXLamp, port | Turns an RCX lamp on (variable is true) or off (variable is false) | output | bool | light.ftl | |
| MotorSpeed, port, brake | Reads / Sets the speed of the motor in degrees per minute. If the speed value is negative, the motor will drive backwards. If the speed is zero, the motor will actively brake until it stops (brake is true) or remove all power and rollout (brake is false). | input output | int | brake is true per default. | motor.ftl |
| MotorIsMoving, port | Sets a variable to true iff the motor on the given port is moving. | input | bool | motor.ftl | |
| MotorRotation, port | 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. | output | int | motor.ftl | |
| Beep, volume | Plays a beep sound as long as the variable is true. | output | bool | default volume is 10 | sound.ftl |
| Buzz, volume | Plays a buzz sound as long as the variable is true. | output | bool | default volume is 10 | sound.ftl |
| BeepSequence, direction, volume | Plays a sequence of tones in either ascending or descending tone frequency if the variable is true. The variable is set to false automatically. | output | bool | direction has to be one of Up, Down default volume is 10 | sound.ftl |
| UltrasonicSensor, port | Reads the distance that an ultrasonic sensor measures. | input | int | ultrasonic.ftl | |
| Gyro, port, mode | Reads the value of a gyroscope. | input | int | Not available on NXT mode hat to be one of Angle, Rate | gyro.ftl |
| CalibrateGyro, port, autoReset | Resets a gyroscope if the variable is true. If autoReset is true, the variable is set to false automatically. | output | bool | autoReset is true per default | gyro.ftl |
...
Using the Remote Console (RConsole)
...
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. | |
| 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. |
input
Overview
Content Tools