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lego-rcx-lejos

Running the leJOS VM on a Lego Mindstorms RCX in 2020 takes some effort. This has been done and documented a few years ago:

Hardware

Recently I got my hands on a Lego Robotics Invention System 1.5 from 1999. It contains an RCX 1.0 without a power jack, two touch sensors, a light sensor, two 9v motors and a serial IR Transmitter Tower. The USB IR Tower is reported not to work on 64-bit systems (no driver). I got the Serial IR Tower working using a LogiLink AU0002E RS232 adapter. And extensive technical details about the RCX hardware are still available: http://www.mralligator.com/rcx/

Original software

The original software (available here: https://philohome.com/sdk25/sdk25.htm) was documented to be designed for Windows(c) 95/98 and doesn't run on my 64-bit Windows 10 computer.

Alternative software

Then I looked for working alternatives to the Lego SDK. A few still available resources are:

RobotC 2.03 (2012): http://www.robotc.net/download/rcx/
BricxCC and NQC: http://bricxcc.sourceforge.net/ and http://bricxcc.sourceforge.net/nqc
BrickOS: http://brickos.sourceforge.net/
Quite C: http://www.elenafrancesco.org/old/lego/qc/index.html
https://pbrick.info/rcx-firmware/
leJOS: http://www.lejos.org/rcx.php

leJOS

I choose leJOS because I know the Java programming language. As the most recent version seems to be the best option to try, I first attempted to get leJOS RCX 3.0 RC2 working but that version turns out to require the USB IR Tower so I switched to leJOS 2.1.0. This version requires working with Java 1.1. Support for Java 1.1 was dropped in the Java Development Kit 1.6 so I got Java SE 5 (JDK) from https://www.oracle.com/java/technologies/java-archive-javase5-downloads.html. Even with this JDK, source code written for Java 4 or Java 5 can't be compiled to Java 1.1 binary class files, so the parameter -source 1.3 must be specified explicitly.

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