[ev3 × Java] leJOS development environment construction (Eclipse on Mac OSX / bluetooth)

I will write about the preparation for running ev3 in Java.

table of contents

0. What is leJOS?
1. What you need
2. Reference article
3. Preparation of microSD
4. bluetooth connection
5. SSH connection
6. Eclipse preparation and program execution Finally

What is 0.leJOS?

A system that provides a Java programming environment for LEGO Mindstorms robots.

This time, I will run ev3 on ** Mac OS X ** using ** bluetooth **. In addition, a program is created and processed using ** Eclipse **, which is a Java integrated development environment.

1. What you need

◯ ev3 (tank) ◯ Personal computer (Eclipse) ◯ bluetooth ◯ microSD ◯ leJOS-API

2. Reference article

I think it's best to read this article and proceed.

[LeJOS] Let's program mindstorm-EV3 in Java [Environment construction first part] [LeJOS] Let's program mindstorm-EV3 in Java [Environment construction part 2]

3. Preparation of microSD

** 1 **. Download the latest from sourceforge / lejos ev3.

** 2 **. Unzip the downloaded one → Unzip sd500.zip.

** 3 **. Use Ethcher to write sd500.img to the sd card.

** 4 **. Unzip lejosimage.zip → Write all the files inside to the SD card. (Drag and drop to move the file to the root directory (top level space) of the SD card.)

• When there is an error that the SD card cannot be written → SD card read only

** 5 **. Download Java for lejos from Oracle JRE.

• The file (ejdk-8-fcs-b132-linux-arm-sflt-03_mar_2014.tar.gz) cannot be used.

** 6 **. Move the downloaded file to the root directory (top level space) of the SD card as it is.

** 7 **. Insert the SD card into ev3 and boot.

4. Make a bluetooth connection

@ev3-brick

** 1 **. Select PAN ** 2 **. Select BT Client ** 3 **. Select the computer you want to connect to ** 4 **. Successful connection when IP address is displayed

5. SSH connection

◯ It is not necessary to execute a general program. Please do it when you need it.

@Terminal

** 1 **. Enter root @ 192. ~. ~. ~

• Enter the IP address displayed on ev3 after @

** 2 ** .Enter key

• You will be asked for the password, but you do not need to enter it.

** 3 **. Confirmation If successful, it will look like ↓ root@EV3:~#

If it doesn't work

** Edit the config file with a vi editor **.

@Terminal

** 1 **. Type cd / etc

** 2 ** .Check if there is a .config file Type `ʻopen ssh``

• If there is no config file Create .ssh / config

** 3 **. Access the .config file cd ssh sudo vi ssh_config Enter your computer password

** 4 ** Edit with .vi editor

Press the i key (INSERT = command to enter characters) Add the following code at the bottom Host 10.0.1.1 192.~.~.~ KexAlgorithms +diffie-hellman-group1-sha1 Ciphers aes128-cbc

• 192. ~. ~. ~ Is the IP address of EV3

Press esc Press the : key Type wq (command to save and exit) Press enter

** 5 **. Check connection ssh root@192.~.~.~

• You will be asked for the password, but you do not need to enter it. If successful, it will look like ↓ root@EV3:~#

[Reference article] Lego EV3 Tutorial with leJOS on macOS How to use the vi command

6. Eclipse preparation and program execution

It is very easy to understand, so please refer to this. [LeJOS] Let's program mindstorm-EV3 in Java [Environment construction part 2]

◯ Sample code example

//Import the required code
import lejos.hardware.*;

//Create a class
public class HelloWorld
{
    //Create a static method
    public static void main(String[] args)
    {
        //Hello World!!And output to the screen of ev3
        System.out.println("Hello World!!");
        //Wait until any button is pressed
        Button.waitForAnyPress();
    }
}

Finally

Thank you for reading. Next time, I would like to write about the control of a single motor. If you find any mistakes or improvements, please let us know.