Questions tagged [lejos]

A Java Virtual Machine that can run on Mindstorms intelligent bricks.

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Unable to open port error

Since today, no matter what program that uses sensors I try to run on my EV3 I get the following error: lejos.hardware.DeviceException: unable to open port at lejos.internal.ev3.EV3Port.open(...
celia's user avatar
  • 11
0 votes
0 answers
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ev3dev vs lejos - looking for a comprehensive comparison

Did anyone make a good comparison of these two environments? The most important factors to me are OS booting time, RAM usage, application start-up time,, compatibility with USB devices, and power ...
Adam S.'s user avatar
  • 11
4 votes
1 answer
533 views

Stuck on "Installing rootfs" when installing leJOS on the brick

When following the instructions for creating an SD card with leJOS, the brick freezes when it comes to the screen “Installing rootfs.” I'm using a new 32 GB SanDisk SD card. I've confirmed that I'm ...
adam.baker's user avatar
3 votes
1 answer
591 views

Two motors are driven forward, why are they rotating in different directions?

I have the Lego Mindstorms EV3 Pack and built a simple car with 3 wheels. The back wheels are motorized. When I run the following code: Motor.A.backward(); Motor.D.Backward(); both motors are ...
weiterleiter's user avatar
2 votes
0 answers
403 views

Is there an leJOS simulator for EV3?

I found this but this seems to be using their own library to control the EV3.
mike's user avatar
  • 21
3 votes
2 answers
768 views

How to get leJOS to run on macOS Sierra

I am working with an eclipse plugin that requires it to run 32bit Java 6 on it and I do have Java 6 on my computer but when I run the program I get this error. Error: This Java instance does not ...
ProgrammingCuber's user avatar
1 vote
0 answers
708 views

EV3 connection problem via USB on Windows 8.1

I am using LEGO EV3 on windows 8.1 eclipse Neon. When I try to launch the class as a LeJos application I get this error. IP address is /10.0.1.1 Creating the jar file or uploading the program failed ...
user8756's user avatar
2 votes
0 answers
2k views

Bluetooth connection to EV3 from Java on Linux/Android

I would like to connect to my EV3 from PC (and then Android) via Bluetooth. I was able to connect to NXT with LEGO-MINDSTORMS-MINDdroid which uses direct LCP commands but as far as I know the ...
rics's user avatar
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1 vote
1 answer
2k views

Where can I find a good tutorial on programming with Lejos?

I want to get started with LeJOS and use Java to check to see if an EV3 touch sensor is pressed, but I can't find any decent tutorials. Are there any good resources for this?
Ken's user avatar
  • 81
3 votes
0 answers
928 views

Sending Gcode to LEGO Mindstorms X/Y plotter?

I am building an x/y plotter out of LEGO Mindstorms. I would like it to read an SVG file on the EV3 Brick, convert it to Gcode, and draw the coordinates. How would I go about doing this?
Ken's user avatar
  • 81
2 votes
1 answer
236 views

Java BufferedImage with Lejos NXT: Java Heap Space

I'm trying to write a program for my Lego Mindstorm NXT, the program is simple, drawing some lines and saving the image in a .png file. So, I thought I'd use BufferedImage and use getGraphics to draw ...
DaPoox's user avatar
  • 23
0 votes
1 answer
376 views

LEGO Mindstorm NXT memorize line followed (LeJos)

I made a line follower program with leJos, it works pretty well; and I want to take it to the next level: I want to make it remember the line it followed; works like this: follow the line till the end,...
DaPoox's user avatar
  • 23
2 votes
1 answer
2k views

usage of ev3 ultrasonic sensor in lejos behavior based programming

I'm using ev3 ultrasonic sensor. And I'm writing a behavior based lejos code. I want to do some tasks when the ultrasonic sensor detects an object which is not further than 30 cm's. And this is my ...
yusuf's user avatar
  • 121
4 votes
0 answers
495 views

RCX + java + usb-to-serial

I am trying to get an old RCX working with leJOS. I already have it working with NQC and BricxCC. While NCQ/BricxCC seems to recognize my usb-to-serial (which appears as "COM5" to the OS), the leJOS ...
Fenn's user avatar
  • 71
6 votes
1 answer
494 views

EV3 RMIregulatedMotor Regulation Problems

I have problem with regulation of the motor when I control EV3 with Bluetooth. Here is the code: RemoteEV3 ev3 = new RemoteEV3("10.0.1.1"); ev3.setDefault(); RMIRegulatedMotor leftMotor = ev3....
Phav Makara's user avatar
7 votes
1 answer
2k views

How to close color Sensor properly?

I want to get data from the color sensor with Bluetooth. I can get data but when the program terminates, the color sensor dose not close even though I call function close() on the color sensor. The ...
Phav Makara's user avatar