Embedded Motion Control/Ubuntu Installation

This document describes how to the install the necessary and sufficient software to start programming your own RCX from LEGO Mindstorms to control your Marslander. After reading this small manual, you should be able to run your own program on the RCX.

Installing Ubuntu 10.04

Ubuntu can be installed according 2 methods

1. Using an USB stick.
2. Using the hard drive.

Note that the second method is more convenient. For both methods the most recent installation instructions can be found on http://www.ubuntu.com/desktop/get-ubuntu/download. Make sure that you download the appropriate architecture i.e. 32 or 64-bit.

Installing the packages

Download the packages

First the following packages need to be downloaded

• brickos 32-bit, 64-bit.
• binutils-h8300-hms 32-bit, 64-bit.
• gcc-h83000-hms 32-bit, 64-bit.
• brickos-doc Download.

The main page can be found at http://packages.ubuntu.com/it/karmic/brickos.

Installing the packages

After all the files are download the installation is as easy as in Windows.

1. Double-click the package.
2. Click install package.
3. After the package is installed it can be closed.

Now a directory can be created for the project files for example /home/ubuntu/emc. Note that the /home/<user> is the same as the user directory in Windows.

Open the terminal, this can be found in Applications->Accessoires->Terminal. In the terminal do the following

ubuntu@ubuntu~$: cd ~
ubuntu@ubuntu~$: mkdir emc
ubuntu@ubuntu~$: cd emc
ubuntu@ubuntu~$: cp -r /usr/share/doc/brickos/examples/demo demo

The first line changes the directory (cd) to the home folder. Then the directory emc is created. Finally the demo directory is copied from the documentation directory.

Now everything is ready to use.

Putting a kernel into the RCX

In order for the RCX to be able to run your programs, it needs to be provided with dedicated firmware. The RCX is equipped with a ROM chip on which the standard Mindstorms firmware is stored. Every time the RCX loses power (e.g. when changing batteries), the firmware which was running on the RCX is replaced by this standard firmware. Therefore, every time the RCX has lost power, the dedicated firmware has to be installed again.

N.B.: If there is already a kernel running on the RCX (not the original one), then this one has to be deleted before a new one can be transferred to it. This can be done by pushing the Prgm button immediately after you push the On-Off button to swith the RCX off (this may take some practice).

First plug in the USB IR tower. To make sure you have permission to use the tower type in the terminal

ubuntu@ubuntu:~$ sudo chmod 666 /dev/usb/legousbtower0

You may test the tower with a simple

ubuntu@ubuntu:~$ echo test > /dev/usb/legousbtower0

The green LED on the tower should light for a second.

To install the firmware for BrickOS, power on your RCX, open the terminal and type

ubuntu@ubuntu:~$ firmdl3 --tty=/dev/usb/legousbtower0  /usr/lib/brickos/brickOS.srec

Now the kernel is being transferred to the RCX and when this is finished, your RCX is ready to be programmed with your own programs.

Downloading your program to the RCX

The programming language used to control the RCX is C. Suppose you wrote a program in C to display "hello world" on the LCD of the RCX. This simple file helloworld.c can be found in the demo directory ~/emc/demo. In order to compile this code we use the command make. This command uses the Makefile already present in the same directory. Therefore, all your C-code should be put into that directory. To compile type

ubuntu@ubuntu:~/emc/demo$ make helloworld.lx

This will start the compilation process and delivers (amongst others) the file helloworld.lx. This is the actual program that will run on the RCX. To download it to the RCX, type

ubuntu@ubuntu:~/emc/demo$ dll --tty=/dev/usb/legousbtower0 helloworld.lx -p1

where the option -pX is used to specify the program number on the RCX, here number 1 (there is room for 7 different programs, hence X is in the range 1 to 7). The program is now loaded on the RCX and by hitting the run button, the text hello world will be displayed on the screen.

If you want the tty part out in the future you may define a local variable by typing

export RCXTTY=/dev/usb/legousbtower0

However when opening a new terminal the local variable does not exist anymore. Therefore it might be convenient to add the line to your .bashrc. Do this by typing

ubuntu@ubuntu:~$ gedit ~/.bashrc

The application gedit will now open, add the line add the bottom of the file, save and close.

Now a second program which plays sound (sound.c) can be compiled and downloaded to the RCX by typing

ubuntu@ubuntu:~/emc/demo$ make sound.lx
ubuntu@ubuntu:~/emc/demo$ dll sound.lx -p3

You can now switch between these two programs (1 & 3) using the Prgm button on the RCX.